When creating a custom component in android it is often asked how to create and pass through the attrs property to the constructor.

It is often suggested that when creating a component in java that you simply use the default constructor, i.e. 

    new MyComponent(context);

rather than attempting to create an attrs object to pass through to the overloaded constructor often seen in xml based custom components. I&#39;ve tried to create an attrs object and it doesn&#39;t seem either easy or at all possible (without an exceedingly complicated process), and by all accounts isn&#39;t really required. 

My question is then: What is the most efficient way of construction a custom component in java that passes or sets properties that would have otherwise been set by the attrs object when inflating a component using xml?





How to pass custom component parameters in java and xml

I&#39;ve read on Wikipedia and other sites about [OSGi][1], but I don&#39;t really see the big picture. It says that it&#39;s a component-based platform, and that you can reload modules at runtime. Also the &quot;practical example&quot; given everywhere is the Eclipse Plugin Framework.

My questions are:

1. What is the clear and simple definition of OSGi?

2. What common problems does it solve?

By &quot;common problems&quot; I mean problems we face everyday, like &quot;What can OSGi do for making our jobs more efficient/fun/simple?&quot;


  [1]: https://en.wikipedia.org/wiki/OSGi

What does OSGi solve?

I am making a component  that contains 3 child components in this way: 

    &lt;header-component&gt;
    &lt;side-component&gt;
    &lt;main-component&gt;

The main component contains list of heroes. 
The header component contains two buttons that are suppose to switch the view on the main component to list or grid view.

The problem I have now is passing data from the header-component to the main component. So when I click grid button the view on the main content should change to grid view , same for the row view.

How can the data be passed between child components in angular 1.5 ? 

How to pass data between sibling components without using $scope?

In React, are there any real differences between these two implementations?
Some friends tell me that the `FirstComponent` is the pattern, but I don&#39;t see why. The `SecondComponent` seems simpler because the render is called only once.

First:

    import React, { PropTypes } from &#39;react&#39;
    
    class FirstComponent extends React.Component {
    
      state = {
        description: &#39;&#39;
      }
    
      componentDidMount() {
        const { description} = this.props;
        this.setState({ description });
      }
    
      render () {
        const {state: { description }} = this;    
        return (
          &lt;input type=&quot;text&quot; value={description} /&gt; 
        );
      }
    }
    
    export default FirstComponent;

Second:

    import React, { PropTypes } from &#39;react&#39;
    
    class SecondComponent extends React.Component {
    
      state = {
        description: &#39;&#39;
      }
    
      constructor (props) =&gt; {
        const { description } = props;
        this.state = {description};
      }
    
      render () {
        const {state: { description }} = this;    
        return (
          &lt;input type=&quot;text&quot; value={description} /&gt;   
        );
      }
    }
    
    export default SecondComponent;


Update:
I changed `setState()` to `this.state = {}` (thanks joews), However, I still don&#39;t see the difference. Is one better than other?

React component initialize state from props

I&#39;ve been watching videos and reading articles but this [specific article][1] make me so confused, at the start of the article it says

&gt; The applications in Angular follow modular structure. The Angular apps will contain many modules, each dedicated to the single purpose. Typically module is a cohesive group of code which is integrated with the other modules to run your Angular apps.
&gt;
&gt; A module exports some classes, function and values from its code. ***The Component is a fundamental block of Angular and multiple components will make up your application.***
&gt;
&gt; A module can be a library for another module. For instance, the angular2/core library which is a primary Angular library module will be imported by another component.


Are they exchangeable terms? Is a component a module? But not viceversa?


  [1]: https://www.tutorialspoint.com/angular2/angular2_modules.htm

What&#39;s the difference between an Angular component and module

This is driving me nuts, I&#39;m under the gun and can&#39;t afford to spend another whole day on this.

I am trying to manually set a control value (&#39;dept&#39;) within the component, and it&#39;s just not working - even the new value logs to console properly.

Here is the FormBuilder Instance:
```typescript    
initForm() {
  this.form = this.fb.group({
    &#39;name&#39;: [&#39;&#39;, Validators.required],
    &#39;dept&#39;: [&#39;&#39;, Validators.required],
    &#39;description&#39;: [&#39;&#39;, Validators.required],
  });
}
```
This is the event handler that receives the selected dept:
```typescript
deptSelected(selected: { id: string; text: string }) {
  console.log(selected) // Shows proper selection!
 
  // This is how I am trying to set the value
  this.form.controls[&#39;dept&#39;].value = selected.id;
}
```
Now when the form is submitted and I log out `this.form` the field is still blank!  I&#39;ve seen other ppl use `updateValue()` but this is beta.1 and I don&#39;t see that as a valid method to call on the control.

I have also tried to call `updateValueAndValidity()` with no success :(.

I would just use `ngControl=&quot;dept&quot;` on the form element, like I&#39;m doing with the rest of the form but its a custom directive/component.
```html
&lt;ng-select
  [data]=&quot;dept&quot;
  [multiple]=&quot;false&quot;
  [items]=&quot;depts&quot;
  (selected)=&quot;deptSelected($event)&quot; &lt;!-- This is how the value gets to me --&gt;
  [placeholder]=&quot;&#39;No Dept Selected&#39;&quot;&gt;
&lt;/ng-select&gt;
```

Manually Set Value for FormBuilder Control

My component has styles that depend on current datetime. In my component I&#39;ve got the following function.

      private fontColor( dto : Dto ) : string {
        // date d&#39;ex&#233;cution du dto
        let dtoDate : Date = new Date( dto.LastExecution );

		(...)

        let color =  &quot;hsl( &quot; + hue + &quot;, 80%, &quot; + (maxLigness - lightnessAmp) + &quot;%)&quot;;
    
        return color;
      }

`lightnessAmp` is calculated from the current datetime. The color changes if `dtoDate` is in the last 24 hours.

The exact error is the following:

&gt; Expression has changed after it was checked. Previous value: &#39;hsl( 123, 80%, 49%)&#39;. Current value: &#39;hsl( 123, 80%, 48%)&#39;

I know the exception appear in development mode only at the moment the value is checked. If the checked value is different of the updated value, the exception is thrown.

So I tried to update the current datetime at each lifecycle in the following hook method to prevent the exception:

      ngAfterViewChecked()
      {
        console.log( &quot;! changement de la date du composant !&quot; );
        this.dateNow = new Date();
      }

...but without success.

How to manage Angular2 &quot;expression has changed after it was checked&quot; exception when a component property depends on current datetime

I want to know if a class can inherit from a class and an interface. 
The example code below doesn&#39;t work but I think it conveys what I want to do.
The reason that I want to do this is because at my company we make USB, serial, Ethernet, etc device. I am trying to develop a generic component/interface that I can use to write programs for all our devices that will help keep the common things (like connecting, disconnecting, getting firmware) the same for all of our applications.

To add to this question:  If GenericDevice is in different project, can I put the IOurDevices interface in that project then then make the USBDevice class implement the interface if I add a reference to the first project? Because would like to just reference one project and then implement different interfaces depending on what the device is.

    class GenericDevice
    {
       private string _connectionState;
       public connectionState
       {
          get{return _connectionState; }
          set{ _connectionState = value;}
       }
    }
    
    interface IOurDevices
    {
       void connectToDevice();
       void DisconnectDevice();
       void GetFirmwareVersion();
    }
    
    class USBDevice : IOurDevices : GenericDevice
    {
       //here I would define the methods in the interface
       //like this...
       void connectToDevice()
       {
           connectionState = &quot;connected&quot;;
       }
    }
    
    //so that in my main program I can do this...
    
    class myProgram
    {
       main()
       {
          USBDevice myUSB = new USBDevice();
          myUSB.ConnectToDevice;
       }
    }


In C#, can a class inherit from another class and an interface?

I am working on an Angular project. I&#39;m struggling with refresh action in a component. &lt;br&gt;&lt;br&gt;
I would like to refresh the router&#39;s components on button click.
I have refresh button when I click on it the component/router need to be refresh.&lt;br&gt;&lt;br&gt;
I tried `window.location.reload()` and `location.reload()` these two are not suitable for my need. Please help if anyone aware of it.
 

How to Refresh a Component in Angular

I have the following simple short-circuit statement that should show either a component or nothing:

`{profileTypesLoading &amp;&amp; &lt;GeneralLoader /&gt;}`

If the statement is false, it renders a `0` instead of nothing.

I have done a `console.log(profileTypesLoading)` just to see quickly what the status of the `profileTypesLoading` property is and it&#39;s either 1 or 0 as expected.  0 should be false... causing nothing to render.  Right?

Any idea why this would happen?

React showing 0 instead of nothing with short-circuit (&amp;&amp;) conditional component

I have just started working with Angular 2. 

I was wondering what are the differences between components and directives in Angular 2?


What is the difference between component and directive?

I want if the input &#39;Contract type&#39; is empty, the button &#39;Save&#39; is not clickable

Save button: 

    &lt;div class=&quot;col-md-4&quot;&gt;
            &lt;cic-textbox [control]=&quot;formGroup.get(&#39;contractType&#39;)&quot;&gt;&lt;/cic-textbox&gt;
          &lt;/div&gt;

ALL Buttons:

     &lt;div class=&quot;cic-header-actions pull-left&quot; *ngIf=&quot;actions &amp;&amp; actions.length &gt; 
     0&quot;&gt;
          &lt;button class=&quot;btn btn-{{action.style}} m-l-xs&quot; *ngFor=&quot;let action of actions&quot; ng-disabled=&quot;!contractTypeValid&quot; (click)=&quot;execute(action)&quot;&gt;
              &lt;cic-icon [icon]=&quot;action.icon&quot;&gt;&lt;/cic-icon&gt;
              {{action.text }}
            &lt;/button&gt;
        &lt;/div&gt;

Definition contractType: 

     let contractType: DataDictionaryPropertyExtended = {
                Binding: &#39;VART:BEZEICHNUNG&#39;,
                Label: &#39;Vertragsart&#39;,
                LabelCols: 4,
                ContentCols: 8,
                IsDisabled: this.isDisabled,
                ValidationProperties: [
                    &lt;ValidationProperty&gt;{
                        Type: ValidationType.IsNotEmpty,
                        ErrorMessage: &#39;Vertragsart darf nicht leer sein.&#39;,
                    }
                ]
            };


BUTTON SAVE GREEN:

[![enter image description here][1]][1]

  [1]: https://i.stack.imgur.com/QE5M2.jpg

Disable Button in Angular 2

These are three different things you can add to a project and I am not quite sure if I understand the difference. They all seem to for example show up in the component toolbox when working with a `Form`. What are some common usage scenarios for each of them? What is the difference?

What is the difference between User Control, Custom Control and Component?

I have a data driven Angular application.  I have a toggle component which I pass in a toggled state.  My issue is that the two way data binding does not seem to work unless i pass in the toggle boolean as an object.  Is there a way to get this to work **without using an EventEmitter or passing the variable in as an object**.  This is to be a reusable component and the application is heavily data driven so passing the value in as an object in not an option.  My code is....

toggle.html

    &lt;input type=&quot;checkbox&quot; [(ngModel)]=&quot;toggled&quot; [id]=&quot;toggleId&quot; name=&quot;check&quot;/&gt;


toggle.component.ts

    import { Component, Input, EventEmitter, Output } from &#39;@angular/core&#39;;

    @Component({
      moduleId: module.id,
      selector: &#39;toggle-switch&#39;,
      templateUrl: &#39;toggle-switch.component.html&#39;,
      styleUrls: [&#39;toggle-switch.component.css&#39;]
    })

    export class ToggleSwitchComponent {

      @Input() toggleId: string;
      @Input() toggled: boolean;

    }

parent.component.html
  

    &lt;toggle-switch toggleId=&quot;toggle-1&quot; [(toggled)]=&quot;nongenericObject.toggled&quot;&gt;&lt;/toggle-switch&gt;

Angular2 Component @Input two way binding

So I&#39;ve created a simple wrapper component with template like:

    &lt;wrapper&gt;
       &lt;b-table v-bind=&quot;$attrs&quot; v-on=&quot;$listeners&quot;&gt;&lt;/b-table&gt;
    &lt;/wrapper&gt;

using `$attrs` and `$listeners` to pass down props and events.   
Works fine, but how can the wrapper proxy the `&lt;b-table&gt;` named slots to the child?

Vue - how to pass down slots inside wrapper component?

First, I am new to Java EE, came from a strong ASP .NET development background.
I have gone through the net, and I might miss this but it seems like there is no simple and straight-to-the-point tutorials on how I could connect backing bean class to a JSF components.

A good example is like this, currently I am trying to create a JSF page where there is a set of links as menu bar and a set of forms. What I am planning to do is, when clicking a link, a particular form will be rendered. 

In ASP.NET, I could easily retrieve the element and then set the attribute to be displayable. I am wondering if there is easy way (heck, even any way) to do this in JSF.

The forms is already in the page, it is just a matter of setting the &quot;render&quot; attribute to true when I click a particular link.

Conditionally displaying JSF components

There are lot of materials out there differentiating `value` attribute and `binding` attribute in JSF.

I&#39;m interested in how both approaches differ from each other. Given:

    public class User {
        private String name;
        private UICommand link;

        // Getters and setters omitted.
    }

&lt;!-- language: lang-xhtml --&gt;

    &lt;h:form&gt;
        &lt;h:commandLink binding=&quot;#{user.link}&quot; value=&quot;#{user.name}&quot; /&gt;
    &lt;/h:form&gt;

It is pretty straight forward what happens when a `value` attribute is specified. The getter runs to return the `name` property value of the `User` bean. The value is printed to HTML output.

But I couldn&#39;t understand how `binding` works. How does the generated HTML maintain a binding with the `link` property of the `User` bean?

Below is the relevant part of the generated output after manual beautification and commenting (note that the id `j_id_jsp_1847466274_1` was auto-generated and that there are two hidden input widgets).
I&#39;m using Sun&#39;s JSF RI, version 1.2.

&lt;!-- language: lang-html --&gt;

	&lt;form action=&quot;/TestJSF/main.jsf&quot; enctype=&quot;application/x-www-form-urlencoded&quot;
	    id=&quot;j_id_jsp_1847466274_1&quot; method=&quot;post&quot;  name=&quot;j_id_jsp_1847466274_1&quot;&gt;
    	&lt;input name=&quot;j_id_jsp_1847466274_1&quot; type=&quot;hidden&quot; value=&quot;j_id_jsp_1847466274_1&quot;&gt;
	    &lt;a href=&quot;#&quot; onclick=&quot;...&quot;&gt;Name&lt;/a&gt;
    	&lt;input autocomplete=&quot;off&quot; id=&quot;javax.faces.ViewState&quot; name=&quot;javax.faces.ViewState&quot;
	    	type=&quot;hidden&quot; value=&quot;-908991273579182886:-7278326187282654551&quot;&gt;
	&lt;/form&gt;

Where is the `binding` stored here?

How does the &#39;binding&#39; attribute work in JSF? When and how should it be used?

I would like to know how to get the value from an input on angular 4.
I looked over the documentation on angular and the example with the key event doesn&#39;t work very well for me and I can&#39;t find a proper example how to do this so please help me out

The problem:
I try to read the input&#39;s value and after submiting the value to another component that will add the value to a select tag(e.g. send the name of the person to a list for a select tag)

  [![My code][1]][1]

  [1]: https://i.stack.imgur.com/okEPd.png

Angular 4 - get input value

I have a component named search_detail which has another component inside it named calendar, 

**SearchDetail_component.html**

     &lt;li class=&quot;date&quot;&gt;
       &lt;div class=&quot;btn-group dropdown&quot; [class.open]=&quot;DatedropdownOpened&quot;&gt;
       &lt;button type=&quot;button&quot; (click)=&quot;DatedropdownOpened = !DatedropdownOpened&quot;   class=&quot;btn btn-default dropdown-toggle&quot; data-toggle=&quot;dropdown&quot;
    aria-haspopup=&quot;true&quot; [attr.aria-expanded]=&quot;dropdownOpened ? &#39;true&#39;: &#39;false&#39;&quot;&gt;
          Date &lt;span class=&quot;caret&quot;&gt;&lt;/span&gt;
      &lt;/button&gt;
      &lt;ul class=&quot;dropdown-menu default-dropdown&quot;&gt;
         &lt;calendar  &gt;&lt;/calendar&gt;
         &lt;button &gt; Cancel &lt;/button&gt;
         &lt;button (click)=&quot;setDate(category)&quot;&gt; Ok &lt;/button&gt;
       &lt;/ul&gt;                            
     &lt;/div&gt;
    &lt;/li&gt;

**SearchDetail_component.ts**

    import &#39;rxjs/add/observable/fromEvent&#39;;
    @Component({
        selector: &#39;searchDetail&#39;,
        templateUrl: &#39;./search_detail.component.html&#39;,
        moduleId: module.id
    
    })

**Calendar.component.ts**

    import { Component, Input} from &#39;@angular/core&#39;; 
    @Component({
        moduleId:module.id,
        selector: &#39;calendar&#39;,
        templateUrl: &#39;./calendar.component.html&#39;
    })
    
        export class CalendarComponent{
          public fromDate:Date = new Date();    
          private toDate:Date = new Date();
          private events:Array&lt;any&gt;;
          private tomorrow:Date;
          private afterTomorrow:Date;
          private formats:Array&lt;string&gt; = [&#39;DD-MM-YYYY&#39;, &#39;YYYY/MM/DD&#39;, &#39;DD.MM.YYYY&#39;, &#39;shortDate&#39;];
          private format = this.formats[0];
          private dateOptions:any = {
            formatYear: &#39;YY&#39;,
            startingDay: 1
          };
          private opened:boolean = false;
        
          public getDate():number {
            return this.fromDate.getDate()  || new Date().getTime();
          }
        }

I want to access the startdate and enddate on click of the ok button in the search detail page. how can i do?

How to Pass data from child to parent component Angular

I have a seemingly trivial question about props and functional components. Basically, I have a container component which renders a Modal component upon state change which is triggered by user click on a button. The modal is a stateless functional component that houses some input fields which need to connect to functions living inside the container component. 

My question: How can I use the functions living inside the parent component to change state while the user is interacting with form fields inside the stateless Modal component? Am I passing down props incorrectly? Thanks in advance.

**Container**

    export default class LookupForm extends Component {
    	constructor(props) {
    		super(props);
    		
    		this.state = {
    			showModal: false
    		};
    	}
    	render() {
    		let close = () =&gt; this.setState({ showModal: false });
    
    		return (
                ... // other JSX syntax
                &lt;CreateProfile fields={this.props} show={this.state.showModal} onHide={close} /&gt;
            );
        }

        firstNameChange(e) {
		  Actions.firstNameChange(e.target.value);
	    }
    };

**Functional (Modal) Component**

    const CreateProfile = ({ fields }) =&gt; {
      console.log(fields);
      return (
          ... // other JSX syntax
          
          &lt;Modal.Body&gt;
            &lt;Panel&gt;
              &lt;div className=&quot;entry-form&quot;&gt;
                &lt;FormGroup&gt;
                  &lt;ControlLabel&gt;First Name&lt;/ControlLabel&gt;
                  &lt;FormControl type=&quot;text&quot;
                    onChange={fields.firstNameChange} placeholder=&quot;Jane&quot;
                    /&gt;
                &lt;/FormGroup&gt;
      );
    };

Example: say I want to call `this.firstNameChange` from within the Modal component. I guess the &quot;destructuring&quot; syntax of passing props to a functional component has got me a bit confused. i.e:

`const SomeComponent = ({ someProps }) = &gt; { // ... };`

React: Passing down props to functional components

I&#39;m using react-select and I&#39;m customizing it,I didn&#39;t found an option to do this. Is there some workaround I can use to keep dropdown open when I&#39;m styling it?

react-select: how to keep dropdown open when styling in inspector?

I have already created a HOC in my react app following [this](https://reactjs.org/docs/higher-order-components.html), and its working fine. However i was wondering if there is a way to create a HOC as functional component(With or without state)??? since the given example is a class based component.

Tried to find the same over web but couldn&#39;t get anything. Not sure if thats even possible?? Or right thing to do ever??

Any leads will be appreciated :)


HOC - Functional Component

&lt;!-- language-all: lang-js --&gt;

How do I mock sub component in jasmine tests?

I have `MyComponent`, which uses `MyNavbarComponent` and `MyToolbarComponent`

    import {Component} from &#39;angular2/core&#39;;
    import {MyNavbarComponent} from &#39;./my-navbar.component&#39;;
    import {MyToolbarComponent} from &#39;./my-toolbar.component&#39;;
    
    @Component({
      selector: &#39;my-app&#39;,
      template: `
        &lt;my-toolbar&gt;&lt;/my-toolbar&gt;
        {{foo}}
        &lt;my-navbar&gt;&lt;/my-navbar&gt;
      `,
      directives: [MyNavbarComponent, MyToolbarComponent]
    })
    export class MyComponent {}

When I test this component, I do not want to load and test those two sub components; MyNavbarComponent, MyToolbarComponent, so I want to mock it.

I know how to mock with services using `provide(MyService, useClass(...))`, but I have no idea how to mock directives; components;

      beforeEach(() =&gt; {
        setBaseTestProviders(
          TEST_BROWSER_PLATFORM_PROVIDERS,
          TEST_BROWSER_APPLICATION_PROVIDERS
        );
        
        //TODO: want to mock unnecessary directives for this component test
        // which are MyNavbarComponent and MyToolbarComponent
      })
      
      it(&#39;should bind to {{foo}}&#39;, injectAsync([TestComponentBuilder], (tcb) =&gt; {
        return tcb.createAsync(MyComponent).then((fixture) =&gt; {
          let DOM = fixture.nativeElement;
          let myComponent = fixture.componentInstance;
          myComponent.foo = &#39;FOO&#39;;
          fixture.detectChanges();
          expect(DOM.innerHTML).toMatch(&#39;FOO&#39;);
        });
      });

Here is my plunker example;

http://plnkr.co/edit/q1l1y8?p=preview

angular2 test, how do I mock sub component

i&#39;m trying to emit function with parameters like that.

    template: `
        &lt;div class=&quot;searchDropDown&quot;&gt;
        &lt;div class=&quot;dropdown is-active&quot;&gt;
        &lt;div class=&quot;dropdown-trigger&quot;&gt;
          &lt;button class=&quot;button&quot; aria-haspopup=&quot;true&quot; aria-controls=&quot;dropdown-menu&quot;&gt;
            &lt;span&gt;{{selectedItem}}&lt;/span&gt;
          &lt;/button&gt;
        &lt;/div&gt;
        &lt;div class=&quot;dropdown-menu&quot; id=&quot;dropdown-menu&quot; role=&quot;menu&quot;&gt;
          &lt;div class=&quot;dropdown-content&quot;&gt;
            &lt;a class=&quot;dropdown-item&quot; v-for=&quot;item in drop&quot; @click=&quot;$emit(&#39;select-menu-item($event)&#39;)&quot;&gt;
              {{item.name}}
            &lt;/a&gt;
          &lt;/div&gt;
        &lt;/div&gt;
      &lt;/div&gt;
        &lt;/div&gt;
      `

here is the i&#39;m trying to pass item to method like a parameter.

here is my component which i try to emit function: 

    &lt;search-component v-bind=&quot;searchProps&quot; @select-menu-item=&quot;selectedITem($event)&quot;&gt;&lt;/search-component&gt;

and here is my method: 

    selectedITem(arg1) {
          console.log(&quot;cl&quot;)
          console.log(arg1)
        }


here is if i&#39;m not trying to pass parameter everything well work so my method **selectedITem** is working. When i try to pass parameter like that nothing happened and i&#39;m not getting some error.

Emit event with parameters in vue

*tl;dr: Basically I want to marry Angular&#39;s `ngOnDestroy` with the Rxjs `takeUntil()` operator. -- is that possible?*

I have an Angular component that opens several Rxjs subscriptions.
These need to be closed when the component is destroyed.

A simple solution for this would be:

    class myComponent {

      private subscriptionA;
      private subscriptionB;
      private subscriptionC;

      constructor(
        private serviceA: ServiceA,
        private serviceB: ServiceB,
        private serviceC: ServiceC) {}

      ngOnInit() {
        this.subscriptionA = this.serviceA.subscribe(...);
        this.subscriptionB = this.serviceB.subscribe(...);
        this.subscriptionC = this.serviceC.subscribe(...);
      }

      ngOnDestroy() {
        this.subscriptionA.unsubscribe();
        this.subscriptionB.unsubscribe();
        this.subscriptionC.unsubscribe();
      }

    }

This works, but it&#39;s a bit redundant. I especially don&#39;t like that
- The `unsubscribe()` is somewhere else, so you gotta remember that these are linked.
- The component state is polluted with the subscription.

I would much prefer using the `takeUntil()` operator or something similar, to make it look like this:

    class myComponent {

      constructor(
        private serviceA: ServiceA,
        private serviceB: ServiceB,
        private serviceC: ServiceC) {}

      ngOnInit() {
        const destroy = Observable.fromEvent(???).first();
        this.subscriptionA = this.serviceA.subscribe(...).takeUntil(destroy);
        this.subscriptionB = this.serviceB.subscribe(...).takeUntil(destroy);
        this.subscriptionC = this.serviceC.subscribe(...).takeUntil(destroy);
      }

    }

Is there a destroy event or something similar that would let me use `takeUntil()` or another way to simplify the component architecture like that?
I realize I could create an event myself in the constructor or something that gets triggered within `ngOnDestroy()` but that would in the end not make things that much simpler to read.

RxJS: takeUntil() Angular component&#39;s ngOnDestroy()

It&#39;s possible to send data from the parent to a child through @Input, or to call a method on the parent from the child with @Output, but I&#39;d like to do exactly the other way around, which is calling a method on the child from the parent. Basically something like that:

&lt;!-- language: typescript --&gt;

    @Component({
      selector: &#39;parent&#39;,
      directives: [Child],
      template: `
    &lt;child
      [fn]=&quot;parentFn&quot;
    &gt;&lt;/child&gt;
    `
    })
    class Parent {
      constructor() {
        this.parentFn()
      }
      parentFn() {
        console.log(&#39;Parent triggering&#39;)
      }
    }

and the child:

&lt;!-- language: typescript --&gt;

    @Component({
      selector: &#39;child&#39;,
      template: `...`
    })
    class Child {
      @Input()
      fn() {
        console.log(&#39;triggered from the parent&#39;)
      }

      constructor() {}
    }

Background is a kind of &quot;get&quot; request, i.e. for getting an up-to-date status from the child.

Now I know I could achieve that with a service and Subject/Observable, but I was wondering whether there is not something more straightforward?

Angular 2 - How to trigger a method on a child from the parent

Is there a decent free API/component for printing barcodes in C#?



Free Barcode API for .NET

I&#39;m trying to figure out how to notify another component about a state change. Let&#39;s say I have 3 components - App.jsx,Header.jsx,and SidebarPush.jsx and all I&#39;m simply trying to do is toggle a class with an onClick.

So the Header.jsx file will have 2 buttons when clicked will toggle the states to true or false. The other 2 components App.jsx and Header.jsx will need to know about these state changes so they can toggle a class
whenever those states change.



App.jsx
-------------------------------------
    
    import React from &#39;react&#39;;
    import Header from &#39;Header&#39;;
    import classNames from &quot;classnames&quot;;
    import SidebarPush from &#39;SidebarPush&#39;;
    import PageWrapper from &#39;PageWrapper&#39;;
    
    var MainWrapper = React.createClass({
        render: function() {
            return (
                &lt;div className={classNames({ &#39;wrapper&#39;: false, &#39;SidebarPush-collapsed&#39;: !this.state.sidbarPushCollapsed })}&gt;
                    &lt;Header/&gt;
                    &lt;SidebarPush/&gt;
                    &lt;PageWrapper&gt;
                    {this.props.children}
                    &lt;/PageWrapper&gt;
                &lt;/div&gt;
            );
        }
    });
    
    module.exports = MainWrapper;
    
    
    
    
Header.jsx
-------------------------------------
    
    
    
    import React from &#39;react&#39;;
    import ReactDom from &#39;react-dom&#39;;
    
    
    class Header extends React.Component {
        constructor() {
            super();
            this.state = {
                sidbarPushCollapsed: false,
                profileCollapsed: false
            };
            this.handleClick = this.handleClick.bind(this);
        }
        handleClick() {
            this.setState({
                sidbarPushCollapsed: !this.state.sidbarPushCollapsed,
                profileCollapsed: !this.state.profileCollapsed
    
            });
        }
        render() {
            return (
                &lt;header id=&quot;header&quot;&gt;
                    &lt;ul&gt;
                        &lt;li&gt;
                            &lt;button type=&quot;button&quot; id=&quot;sidbarPush&quot; onClick={this.handleClick} profile={this.state.profileCollapsed}&gt;
                                &lt;i className=&quot;fa fa-bars&quot;&gt;&lt;/i&gt;
                            &lt;/button&gt;
                        &lt;/li&gt;
                        &lt;li&gt;
                            &lt;button type=&quot;button&quot; id=&quot;profile&quot; onClick={this.handleClick}&gt;
                                &lt;i className=&quot;icon-user&quot;&gt;&lt;/i&gt;
                            &lt;/button&gt;
                        &lt;/li&gt;
                    &lt;/ul&gt;
                    &lt;ul&gt;
                        &lt;li&gt;
                            &lt;button id=&quot;sidbarOverlay&quot; onClick={this.handleClick}&gt;
                                &lt;i className=&quot;fa fa-indent&quot;&gt;&lt;/i&gt;
                            &lt;/button&gt;
                        &lt;/li&gt;
                    &lt;/ul&gt;
                &lt;/header&gt;
            );
        }
    };
    
    module.exports = Header;
    
    
    
    
SidebarPush.jsx
-------------------------------------
    
    import React from &#39;react&#39;;
    import ReactDom from &#39;react-dom&#39;;
    import classNames from &quot;classnames&quot;;
    
    
    class SidebarPush extends React.Component {
        render() {
            return (
                &lt;aside className=&quot;sidebarPush&quot;&gt;
                    &lt;div className={classNames({ &#39;sidebar-profile&#39;: true, &#39;hidden&#39;: !this.state.pagesCollapsed })}&gt;
                            ....
                    &lt;/div&gt;
                      
                    &lt;nav className=&quot;sidebarNav&quot;&gt;
                            ....
                    &lt;/nav&gt;
                &lt;/aside&gt;
            );
        }
    }
    
    
    export default SidebarPush;




React - how to pass state to another component

I have a scenario where I&#39;m passing data from a reducer into my react state. 

data:

    {
        &quot;id&quot;: 1,
        &quot;title&quot;: &quot;Test&quot;,
        &quot;content&quot;: {
            &quot;body&quot;: &quot;sdfsdf&quot;
            &quot;image&quot;: &quot;http://example.com&quot;
        }
    }


Using componentWillRecieveProps, this works perfectly for retrieving the title.

    componentWillReceiveProps(nextProps) {
        this.setState({
            title: nextProps.blog.title,
        })
    }

However, I&#39;m having difficulty retrieving the nested fields. When I do this:

    componentWillReceiveProps(nextProps) {
        console.log(&quot;new title is&quot;, nextProps.blog.title);
        console.log(&quot;new body content is&quot;, nextProps.blog.content[&quot;body&quot;]);
        this.setState({
            title: nextProps.blog.title,
            body: nextProps.blog.content[&quot;body&quot;]
        })
    }

I get this error: 

[![enter image description here][1]][1]

The error of an undefined body goes away after I click the debugger and the content is loaded. Is there anyway I can combat this issue? 

I tried to check for undefined like this:

    if (typeof nextProps.blog.content[&quot;body&quot;] != &#39;undefined&#39;){

But this doesn&#39;t work either and I believe it&#39;s because the blog is undefined. 


  [1]: https://i.stack.imgur.com/1bsyD.png

Checking for Undefined In React

I created a Plexus component to house common logic for several Mojos I want to create. I have been able to pass information like `localRepository` and project from the Mojo (and test cases).

I was wondering if there is a way to get the `MavenSession` or `MavenExecutionRequest` from within the component without having to pass them as parameters from a Mojo. I know my component will be running from a Maven Mojo.

I&#39;m using Maven 2 in this instance.

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