    if (__DEV__) {
        console.log(&#39;I am in debug&#39;);
    }

You can [see this approach][1] is being used in [React Native repository][2].


  [1]: https://github.com/facebook/react-native/search?p=1&amp;q=__DEV__&amp;unscoped_q=__DEV__
  [2]: https://github.com/facebook/react-native

I created a docker container from my OS X VM Docker host.  I created it using the run command and created the container based off the `ubuntu:xenial` image off docker hub.

I&#39;m now connected to my container after it&#39;s created and logged in as root and at the command prompt inside my container.

I tried to install homebrew and for some reason, I can&#39;t run the command to install Homebrew:

    ruby -e &quot;$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)&quot;

when I run that I get a bash:

&gt; curl: command not found

Not sure why I&#39;m not able to use curl here inside my container.

Can&#39;t run Curl command inside my Docker Container

I was trying to remove unwanted characters from a given string using `text.translate()` in Python 3.4.

The minimal code is:

	import sys 
	s = &#39;abcde12345@#@$#%$&#39;
	mapper = dict.fromkeys(i for i in range(sys.maxunicode) if chr(i) in &#39;@#$&#39;)
	print(s.translate(mapper))

It works as expected. However the same program when executed in Python 3.4 and Python 3.5 gives a large difference.

The code to calculate timings is

	python3 -m timeit -s &quot;import sys;s = &#39;abcde12345@#@$#%$&#39;*1000 ; mapper = dict.fromkeys(i for i in range(sys.maxunicode) if chr(i) in &#39;@#$&#39;); &quot;   &quot;s.translate(mapper)&quot;

The Python 3.4 program takes ***1.3ms*** whereas the same program in Python 3.5 takes only ***26.4μs***. 

What has improved in Python 3.5 that makes it faster compared to Python 3.4?

Why is str.translate much faster in Python 3.5 compared to Python 3.4?

I&#39;d like to add some debug-only UI to my React Native app, but I can&#39;t find any equivalent of `RCT_DEBUG` or `RCT_DEV` compile-time flags in the JavaScript environment. Is there one?

Use case: I want to add a status bar that shows the number of HTTP requests initiated by my app. Obviously this is not part of a shipping app, but it would help me check my work while in development and testing.

How can I determine if my React Native app is a debug or release build from JavaScript code?

<p>I'd like to add some debug-only UI to my React Native app, but I can't find any equivalent of <code>RCT_DEBUG</code> or <code>RCT_DEV</code> compile-time flags in the JavaScript environment. Is there one?</p>
<p>Use case: I want to add a status bar that shows the number of HTTP requests initiated by my app. Obviously this is not part of a shipping app, but it would help me check my work while in development and testing.</p>


I&#39;m trying to load a splash screen for an iOS app built in React Native. I&#39;m trying to accomplish this through class states and then a setTimeout function as follows:

&lt;!-- begin snippet: js hide: false --&gt;

&lt;!-- language: lang-html --&gt;

    class CowtanApp extends Component {
      constructor(props){
        super(props);
        this.state = {
          timePassed: false
        };
      }

      render() {
        setTimeout(function(){this.setState({timePassed: true})}, 1000);
        if (!this.state.timePassed){
          return &lt;LoadingPage/&gt;;
        }else{
          return (
            &lt;NavigatorIOS
              style = {styles.container}
              initialRoute = {{
                component: LoginPage,
                title: &#39;Sign In&#39;,
              }}/&gt;
          );
        }
      }
    }

The loading page works for a second, and then I guess when setTimeout tries to change the state to true, my program crashes: &#39;undefined is not an object (evaluating this.setState)&#39;. I&#39;ve been going at this for a couple of hours, any ideas on how to fix it?

setTimeout in React Native

I just came across this concept of 

    var copy = Object.assign({}, originalObject);

which creates a copy of original object into the &quot;`copy`&quot; object. However, my question is, does this way of cloning object create a deep copy or a shallow copy? 

PS: The confusion is, if it creates a deep copy, then it would be the easiest way to clone an object.

JS: Does Object.assign() create deep copy or shallow copy

I&#39;m a bit fuzzy on these concepts, If I build the same ToDo app completely in AngularJS and ReactJS--- what makes the React ToDo use one-way data binding vs the AngularJS&#39;s two-way data binding?

I understand that React sort of works like 

Render(data) ---&gt; UI.

How is this different from Angular?


Can anyone explain the difference between Reacts one-way data binding and Angular&#39;s two-way data binding

I am new to ReactJS and JSX and I am having a little problem with the code below. 

I am trying to add multiple classes to the `className` attribute on each `li`:

    


&lt;!-- language: lang-html --&gt;

    &lt;li key={index} className={activeClass, data.class, &quot;main-class&quot;}&gt;&lt;/li&gt;


My React component is:

    


&lt;!-- language: lang-jsx --&gt;

    var AccountMainMenu = React.createClass({
      getInitialState: function() {
        return { focused: 0 };
      },

      clicked: function(index) {
        this.setState({ focused: index });
      },

      render: function() {
        var self = this;
        var accountMenuData = [
          {
            name: &quot;My Account&quot;,
            icon: &quot;icon-account&quot;
          },
          {
            name: &quot;Messages&quot;,
            icon: &quot;icon-message&quot;
          },
          {
            name: &quot;Settings&quot;,
            icon: &quot;icon-settings&quot;
          }
        /*{
            name:&quot;Help &amp;amp; Support &amp;nbsp; &lt;span class=&#39;font-awesome icon-support&#39;&gt;&lt;/span&gt;(888) 664.6261&quot;,
            listClass:&quot;no-mobile last help-support last&quot;
          }*/
        ];

        return (
          &lt;div className=&quot;acc-header-wrapper clearfix&quot;&gt;
            &lt;ul className=&quot;acc-btns-container&quot;&gt;
              {accountMenuData.map(function(data, index) {
                var activeClass = &quot;&quot;;

                if (self.state.focused == index) {
                  activeClass = &quot;active&quot;;
                }

                return (
                  &lt;li
                    key={index}
                    className={activeClass}
                    onClick={self.clicked.bind(self, index)}
                  &gt;
                    &lt;a href=&quot;#&quot; className={data.icon}&gt;
                      {data.name}
                    &lt;/a&gt;
                  &lt;/li&gt;
                );
              })}
            &lt;/ul&gt;
          &lt;/div&gt;
        );
      }
    });

    ReactDOM.render(&lt;AccountMainMenu /&gt;, document.getElementById(&quot;app-container&quot;));





How to add multiple classes to a ReactJS Component?

I am looking for an example in handling Bubbling and Capturing in React.js. I found [one with JavaScript][1], but I am having trouble finding the equivalent for React.js.

How would I have to create an example for Bubbling and Capturing in React.js?


  [1]: https://stackoverflow.com/questions/4616694/what-is-event-bubbling-and-capturing

Example for Bubbling and Capturing in React.js

I want to realize a function about changing password. It requires users to input their previous password in an alert dialog.

I want to click the button &quot;Confirm the modification&quot; then jump to the other view controller for changing password. I have written some code, but I don&#39;t know how to write in the next moment.

```
UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@&quot;Change password&quot; message:@&quot;Please input your previous password&quot; preferredStyle:UIAlertControllerStyleAlert];

[alertController addTextFieldWithConfigurationHandler:^(UITextField *textField) {
	textField.placeholder = @&quot;please input your previous password&quot;;
	textField.secureTextEntry = YES;
}];

UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@&quot;cancel&quot; style:UIAlertActionStyleCancel handlers:nil];

UIAlertAction *okAction = [UIAlertAction actionWithTitle:@&quot;Confirm the modification&quot; style:UIAlertActionStyleDestructive handler:*(UIAlertAction *alertAction) {
	if (condition) {
		statements
	}
}];

[alertController addAction:cancelAction];
[alertController addAction:okAction];
[self presentViewController:alertController animated:YES completion:nil];
```

[![enter image description here][2]][2]

  [1]: http://i.stack.imgur.com/LwpuY.png
  [2]: http://i.stack.imgur.com/C0IEe.png

How to add textField in UIAlertController?

My podfile was working but after updating to cocoapods version 1.0.0.beta.1

pod install displays following error

    MacBook-Pro:iOS-TuneIn home$ pod install
    Fully deintegrating due to major version update
    Deleted 1 &#39;Copy Pods Resources&#39; build phases.
    Deleted 1 &#39;Check Pods Manifest.lock&#39; build phases.
    Deleted 1 &#39;Embed Pods Frameworks&#39; build phases.
    - libPods.a
    - Pods.debug.xcconfig
    - Pods.release.xcconfig
    Deleted 1 &#39;Copy Pods Resources&#39; build phases.
    Deleted 1 &#39;Check Pods Manifest.lock&#39; build phases.
    - libPods.a
    Deleted 1 &#39;Copy Pods Resources&#39; build phases.
    Deleted 1 &#39;Check Pods Manifest.lock&#39; build phases.
    - libPods.a
    Deleted 1 &#39;Copy Pods Resources&#39; build phases.
    Deleted 1 &#39;Check Pods Manifest.lock&#39; build phases.
    - libPods.a
    Deleted 1 &#39;Copy Pods Resources&#39; build phases.
    Deleted 1 &#39;Check Pods Manifest.lock&#39; build phases.
    - libPods.a
    - libPods.a
    Deleted 1 empty `Pods` groups from project.
    Removing `Pods` directory.
    
    Project has been deintegrated. No traces of CocoaPods left in project.
    Note: The workspace referencing the Pods project still remains.
    Updating local specs repositories
    Analyzing dependencies
    [!] The dependency `AFNetworking (= 2.6.3)` is not used in any concrete target.
    The dependency `MBProgressHUD (~&gt; 0.9.1)` is not used in any concrete target.
    The dependency `PDKeychainBindingsController (~&gt; 0.0.1)` is not used in any concrete target.
    The dependency `FMDB/SQLCipher` is not used in any concrete target.
    The dependency `ZXingObjC (~&gt; 3.1.0)` is not used in any concrete target.
    The dependency `SDWebImage (~&gt; 3.7.2)` is not used in any concrete target.
    The dependency `SignalR-ObjC (~&gt; 2.0.0.beta3)` is not used in any concrete target.
    The dependency `CJPAdController (from `https://github.com/nabeelarif100/CJPAdController.git`)` is not used in any concrete target.
    The dependency `ECSlidingViewController (~&gt; 2.0.3)` is not used in any concrete target.
    The dependency `VGParallaxHeader` is not used in any concrete target.
    The dependency `EMString` is not used in any concrete target.
    The dependency `Google/SignIn` is not used in any concrete target.
    The dependency `VIPhotoView (~&gt; 0.1)` is not used in any concrete target.
    The dependency `EncryptedCoreData (from `https://github.com/project-imas/encrypted-core-data.git`)` is not used in any concrete target.
    MacBook-Pro:iOS-TuneIn home$ 

Podfile:

    source &#39;https://github.com/CocoaPods/Specs.git&#39;
    platform :ios, &#39;7.0&#39;
    pod &#39;AFNetworking&#39;, &#39;2.6.3&#39;
    pod &#39;MBProgressHUD&#39;, &#39;~&gt; 0.9.1&#39;
    pod &#39;PDKeychainBindingsController&#39;, &#39;~&gt; 0.0.1&#39;
    pod &#39;FMDB/SQLCipher&#39;
    pod &#39;ZXingObjC&#39;, &#39;~&gt; 3.1.0&#39;
    pod &#39;SDWebImage&#39;, &#39;~&gt;3.7.2&#39;
    pod &#39;SignalR-ObjC&#39;,&#39;~&gt;2.0.0.beta3&#39;
    pod &#39;CJPAdController&#39;, :git =&gt; &#39;https://github.com/nabeelarif100/CJPAdController.git&#39;
    pod &#39;ECSlidingViewController&#39;, &#39;~&gt; 2.0.3&#39;
    pod &#39;VGParallaxHeader&#39;
    pod &#39;EMString&#39;
    pod &#39;Google/SignIn&#39;
    pod &#39;VIPhotoView&#39;, &#39;~&gt; 0.1&#39;
    pod &#39;EncryptedCoreData&#39;, :git =&gt; &#39;https://github.com/project-imas/encrypted-core-data.git&#39;

Pod install displaying error in cocoapods version 1.0.0.beta.1

In Interface Builder, I use a horizontal UIStackView and want to place the items as this :

       xx   xx   xx
every x symbolize an item. Item1 and item2 should be stuck one to the other, but item2 and item3 should be spaced and so on. That means I do not want constant spacing between all the items.

How can I do so ?  
(maybe an equivalent of flexible space of toolbars) 

Thanks !

Setting space between some items in stack view

I&#39;ve tried many cases, but none work for me. I tried:

    if resultTitles[indexPath.row].rangeOfCharacterFromSet(badCharacters) == nil {
        let badCharacters = NSCharacterSet.decimalDigitCharacterSet().invertedSet
        print(&quot;Index: \(indexPath.row)&quot;)
    }

also tried to 

    if ((resultTitles[0].toInt()) != nil) {
        print(&quot;ERROR&quot;)
    }

So, how can I check that my text contains only numbers?

How to check if text contains only numbers?

Ionic is awesome, but if you want to stay in the React-native world, I haven&#39;t found anything comparable and compatible. Let me know if you have any suggestions?

Is there any style framework for react-native similar to bootstrap for web?

I built an app with **ReactNative** both for iOS and android with a [`ListView`][1]. When populating the listview with a valid datasource, the following warning is printed at the bottom of the screen:

&gt; Warning: Each child in an array or iterator should have a unique &quot;key&quot;
&gt; prop. Check the render method of `ListView`.

What is the purpose of this warning? After the message they link to [this page](https://reactjs.org/docs/lists-and-keys.html#keys), where complete different things are discussed which have nothing to do with react native, but with web based reactjs.

My ListView is built with those statements:

    render() {
		var store = this.props.store;

        return (

            &lt;ListView
                dataSource={this.state.dataSource}
				renderHeader={this.renderHeader.bind(this)}
                renderRow={this.renderDetailItem.bind(this)}
				renderSeparator={this.renderSeparator.bind(this)}
                style={styles.listView}
                /&gt;

        );
    }

My DataSource consists of something like:

		var detailItems = [];

		detailItems.push( new DetailItem(&#39;plain&#39;, store.address) );
		detailItems.push( new DetailItem(&#39;map&#39;, &#39;&#39;) );

		if(store.telefon) {
			detailItems.push( new DetailItem(&#39;contact&#39;, store.telefon, &#39;Anrufen&#39;, &#39;fontawesome|phone&#39;) );
		}
		if(store.email) {
			detailItems.push( new DetailItem(&#39;contact&#39;, store.email, &#39;Email&#39;, &#39;fontawesome|envelope&#39;) );
		}
		detailItems.push( new DetailItem(&#39;moreInfo&#39;, &#39;&#39;) );

        this.setState({
            dataSource: this.state.dataSource.cloneWithRows(detailItems)
        });

And the ListView-Rows are rendered with stuff like:

			return (
				&lt;TouchableHighlight underlayColor=&#39;#dddddd&#39;&gt;
	                &lt;View style={styles.infoRow}&gt;
						&lt;Icon
						            name={item.icon}
						            size={30}
						            color=&#39;gray&#39;
						            style={styles.contactIcon}
						            /&gt;
						&lt;View style={{ flex: 1}}&gt;
							&lt;Text style={styles.headline}&gt;{item.headline}&lt;/Text&gt;
	                        &lt;Text style={styles.details}&gt;{item.text}&lt;/Text&gt;
						&lt;/View&gt;
                        &lt;View style={styles.separator}/&gt;
	                &lt;/View&gt;
	            &lt;/TouchableHighlight&gt;
	        );

Everything works fine and as expected, except the warning which seems to be complete nonsense to me.

Adding a key-property to my &quot;DetailItem&quot;-Class didn&#39;t solve the issue.

This is, what really will be passed to the ListView as a result of &quot;cloneWithRows&quot;:

    _dataBlob: 
    I/ReactNativeJS( 1293):    { s1: 
    I/ReactNativeJS( 1293):       [ { key: 2,
    I/ReactNativeJS( 1293):           type: &#39;plain&#39;,
    I/ReactNativeJS( 1293):           text: &#39;xxxxxxxxxx&#39;,
    I/ReactNativeJS( 1293):           headline: &#39;&#39;,
    I/ReactNativeJS( 1293):           icon: &#39;&#39; },
    I/ReactNativeJS( 1293):         { key: 3, type: &#39;map&#39;, text: &#39;&#39;, headline: &#39;&#39;, icon: &#39;&#39; },
    I/ReactNativeJS( 1293):         { key: 4,
    I/ReactNativeJS( 1293):           type: &#39;contact&#39;,
    I/ReactNativeJS( 1293):           text: &#39;(xxxx) yyyyyy&#39;,
    I/ReactNativeJS( 1293):           headline: &#39;Anrufen&#39;,
    I/ReactNativeJS( 1293):           icon: &#39;fontawesome|phone&#39; },
    I/ReactNativeJS( 1293):         { key: 5,
    I/ReactNativeJS( 1293):           type: &#39;contact&#39;,
    I/ReactNativeJS( 1293):           text: &#39;xxxxxxxxx@hotmail.com&#39;,
    I/ReactNativeJS( 1293):           headline: &#39;Email&#39;,
    I/ReactNativeJS( 1293):           icon: &#39;fontawesome|envelope&#39; },
    I/ReactNativeJS( 1293):         { key: 6, type: &#39;moreInfo&#39;, text: &#39;&#39;, headline: &#39;&#39;, icon: &#39;&#39; } ] },


As one key see, each record has a key property. The warning still exists.

  [1]: https://facebook.github.io/react-native/docs/listview.html#content

Warning: Each child in an array or iterator should have a unique &quot;key&quot; prop. Check the render method of `ListView`

I&#39;m trying to format a Date String in React Native.

Ex: 2016-01-04 10:34:23

Following is the code I&#39;m using.

    var date = new Date(&quot;2016-01-04 10:34:23&quot;);
    console.log(date);

My problem is, when I&#39;m emulating this on a iPhone 6S, it&#39;ll print Mon `Jan 04 2016 10:34:23 GMT+0530 (IST)` without any problem. But if I try with the iPhone 5S it prints nothing. And if you try to get the month by using a method like `date.getMonth()` it&#39;ll print `&quot;NaN&quot;`.

Why is this? What is the workaround?

Formatting a Date String in React Native

React Native doesn&#39;t support the CSS ```display``` property, and by default all elements use the behavior of ```display: flex``` (no ```inline-flex``` either). Most non-flex layouts can be simulated with flex properties, but I&#39;m flustered with inline text.

My app has a container that contains several words in text, some of which need formatting. This means I need to use spans to accomplish the formatting. In order to achieve wrapping of the spans, I can set the container to use ```flex-wrap: wrap```, but this will only allow wrapping at the end of a span rather than the traditional inline behavior of wrapping at word breaks.

The problem visualized (spans in yellow):

[![enter image description here][1]][1]

(via http://codepen.io/anon/pen/GoWmdm?editors=110)

Is there a way to get proper wrapping and true inline simulation using flex properties?





  [1]: http://i.stack.imgur.com/CgR94.png

Content Type	Original Author	Original Content on Stackoverflow
Question	escouten	View Question on Stackoverflow
Solution 1 - Javascript	rmevans9	View Answer on Stackoverflow

How can I determine if my React Native app is a debug or release build from JavaScript code?

Javascript Problem Overview

Javascript Solutions

Solution 1 - Javascript

Why is str.translate much faster in Python 3.5 compared to Python 3.4?

Can't run Curl command inside my Docker Container

Attributions