I&#39;ve used both extensively. We have been using React Native in production for about 5 months now, and have previously worked with Ionic / Angular, and Phonegap projects for 3 years.

Here are the pros and cons of React Native, in my opinion, from someone who has fairly extensive experience in both. I&#39;m not going to go into Ionic since you already have some experience there.

**React Native Cons:**

1. New technologies that you have to learn (React if you haven&#39;t already used it, Android environment &amp; understanding of Xcode)
2. New data architecture and frameworks (Redux/Mobx/Flux/Reflux/etc...)
3. Fairly new and documentation is still coming along but not completely there yet (Though the community is amazing at helping answer questions)
4. Learning how to style React Native is just similar enough to CSS to get you in trouble and frustrate you in the beginning

**React Native Pros:**

1. Very fast development time
2. Amazing user experience when loaded on device (true native feel in my experience vs hybrid)
3. Hot reloading
4. Flux &amp; similar data architecture (once you learn and understand it)
5. Fun to build once you learn it
6. Not a steep learning curve
7. Amazing community

If I were to meet someone and recommend one over the other I would definitely recommend React Native. That being said, PhoneGap / Cordova and Ionic are all still very solid and if you feel productive and are not in the position to spend some time learning a new technology, I would say stick with one of those.

[C++ Core Guidelines][1] has been presented recently (congrats!) and I am concerned about `gsl::not_null` type. As stated in [I.12: Declare a pointer that must not be null as `not_null`][2]:

&gt; To help avoid dereferencing nullptr errors. To improve performance by
&gt; avoiding redundant checks for nullptr. 
&gt;
&gt; ... 
&gt;
&gt; By stating the intent in
&gt; source, implementers and tools can provide better diagnostics, such as
&gt; finding some classes of errors through static analysis, and perform
&gt; optimizations, such as removing branches and null tests.

The intent is clear. However, we already have a language feature for that. Pointers that cannot be null are called references. And while references cannot be rebound once they are created, this problem is solved by `std::reference_wrapper`. 

The main difference between `gsl::not_null` and `std::reference_wrapper` I see in that the latter can be used only instead of pointers, while the former works on anything `nullptr`-assignable (quote from  [F.17: Use a not_null&lt;T&gt; to indicate that &quot;null&quot; is not a valid value][3]):

&gt; `not_null` is not just for built-in pointers. It works for
&gt; `array_view`, `string_view`, `unique_ptr`, `shared_ptr`, and other
&gt; pointer-like types.

I imagine the feature comparison table like the following:

`T&amp;`:

* Cannot store `nullptr`? - **Yes**
* Rebindable? - **No**
* Can be used instead of something other than pointers? - **No**

`std::reference_wrapper&lt;T&gt;`:

* Cannot store `nullptr`? - **Yes**
* Rebindable? - **Yes**
* Can be used instead of something other than pointers? - **No**

`gsl::not_null&lt;T*&gt;`:

* Cannot store `nullptr`? - **Yes**
* Rebindable? - **Yes**
* Can be used instead of something other than pointers? - **Yes**

Now here are the questions, finally:

1. Is my understanding of differences between these concepts correct?
2. Does that mean that `std::reference_wrapper` is now useless?

**PS** I created tags `cpp-core-guidelines` and `guideline-support-library` for this, I hope properly.


  [1]: https://github.com/isocpp/CppCoreGuidelines
  [2]: https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#-i12-declare-a-pointer-that-must-not-be-null-as-not_null
  [3]: https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#-f17-use-a-not_nullt-to-indicate-that-null-is-not-a-valid-value

gsl::not_null&lt;T*&gt; vs. std::reference_wrapper&lt;T&gt; vs. T&amp;

I am coming from MySQL, and in MySQL you can use AUTOINCREMENT for a row&#39;s unique id as the primary key.

I find that there is no AUTOINCREMENT in Postgresql, only SEQUENCE or UUID.I have read somewhere that we can use UUID as the primary key of a table. This has the added advantage of masking other user&#39;s id (as I want to build APIs that take the ID in as a parameter). Which should I use for Postgresql?

UUID or SEQUENCE for primary key?

I&#39;m embarking on a side project. Its a native hybrid app. I&#39;ve used Phonegap / Ionic / Angular a lot to build apps quickly. I&#39;m researching React Native at the moment. 
Has anyone who&#39;s used both of these have any comments or +/- about each one?

Phone gap vs React Native

<p>I'm embarking on a side project. Its a native hybrid app. I've used Phonegap / Ionic / Angular a lot to build apps quickly. I'm researching React Native at the moment.
Has anyone who's used both of these have any comments or +/- about each one?</p>


I just created one new cordova ios project via CLI, and i opened that project in Xcode 7.1 and while running on simulator am getting some error on mainViewController.xib, if we clicked on that error its showing xib file and on top of that showing one warning message  &quot;An internal error occurred. Editing functionality may be limited&quot; . So am unable to run this project.


I don&#39;t know whether this is due to Xcode bug or cordova bug or any other settings issue in my Xcode.

 
 [![enter image description here][1]][1]


  [1]: http://i.stack.imgur.com/Pk3pr.png

IOS project showing error &quot;An internal error occurred. Editing functionality may be limited&quot; on xcode 7.1

This **error occur only** when I try to `cordova run ios --device`

Even after `cordova build ios` command executed, non error is reported.

Whats I do wrong? And how to debug cordova projects on my iPhone (need this because need to test a Camera feature)


    WITH CONFIGURATION Debug ===
    
    Check dependencies
    Code Sign error: No provisioning profiles found: No non–expired provisioning profiles were found.
    
    ** BUILD FAILED **
    
    
    The following build commands failed:
            Check dependencies
    (1 failure)
    Error code 65 for command: xcodebuild with args: -xcconfig,/Users/ridermansb/Projects/jdapp/platforms/ios/cordova/build-debug.xcconfig,-project,CorrijaMe.xcodeproj,ARCHS=armv7 armv7s arm64,-target,CorrijaMe,-configuration,Debug,-sdk,iphoneos,build,VALID_ARCHS=armv7 armv7s arm64,CONFIGURATION_BUILD_DIR=/Users/ridermansb/Projects/jdapp/platforms/ios/build/device,SHARED_PRECOMPS_DIR=/Users/ridermansb/Projects/jdapp/platforms/ios/build/sharedpch
    ERROR running one or more of the platforms: Error: /Users/ridermansb/Projects/jdapp/platforms/ios/cordova/run: Command failed with exit code 2
    You may not have the required environment or OS to run this project


cordova run with ios error .. Error code 65 for command: xcodebuild with args:

So I know this has been questioned quite a lot. To be exact for example in these questions:  

1. https://stackoverflow.com/questions/31111377/run-nodejs-server-in-android  
2. https://stackoverflow.com/questions/11392590/how-to-run-my-node-js-project-on-android?lq=1  
and   
3. https://stackoverflow.com/questions/29145308/nodejs-on-ios-android?rq=1

Every option presented has a problem though:

 - I want to run it on my normal device so I would like to avoid installing another OS on my Device
 
 - Work on JXCore was stopped last month and (maybe as a result) I couldn&#39;t get it to compile (see https://stackoverflow.com/questions/36506305/cant-install-jxcore-cordova)
 - The Android Port of NodeJs [Anode](https://github.com/paddybyers/anode) has not been worked on since 2014 and wasn&#39;t really maintained back then anyways
 - The second answer in the second thread I linked to mentioned there is an official node distribution for Android now but apart from a link to the [Browse-Website of the latest dist](https://nodejs.org/dist/latest/) I couldn&#39;t find any info on how to actually use it
 - I also saw [this](http://www.goland.org/nodejsonandroid/) but it seems like the device has to be connected to a PC (or similar) to run the adb shell commands while I would like to make it as a separate App

With the time that past since these questions have been posted and as the &quot;best option&quot; JXCore seem to be now unusable:  
Is there a way to run a node.js application (a server in my case) on an Android device?

if you&#39;re wondering why I&#39;d want this: I made a WebApp with a Node.Js server and I now want a version you can launch locally from your phone without requiring an Internet connection. This means the server needs to run on an Android phone.


Running Node.Js on Android

My apologies if this is a very simple question, but how do you use google material icons without a  

    &lt;link href=&quot;https://fonts.googleapis.com/icon?family=Material+Icons&quot; rel=&quot;stylesheet&quot;&gt; 
?

I would like my app to be able to display the icons even when the user does not have an internet connection

How to host material icons offline?

After typing `cordova run android` in terminal, I&#39;m getting this error:

    Waiting for emulator to start...
    PANIC: Broken AVD system path. Check your ANDROID_SDK_ROOT value [/Users/username/Library/Android/sdk]!

This happens after exporting:

    export ANDROID_SDK_ROOT=&#39;/Users/username/Library/Android/sdk&#39;

Before exporting I got:

    Waiting for emulator to start...
    PANIC: Cannot find AVD system path. Please define ANDROID_SDK_ROOT

Any ideas where I&#39;m going wrong? I&#39;m sure this is the sdk root so why am I getting broken avd system path?


PANIC: Broken AVD system path. Check your ANDROID_SDK_ROOT value

I have already read several flexbox tutorial, but I still cannot make this simple task to work.

How can I make the red box to 100% width?

[![enter image description here][1]][1]

Code:

      &lt;View style={styles.container}&gt;
        &lt;Text style={styles.welcome}&gt;
          Welcome to React Natives
        &lt;/Text&gt;
        &lt;Text style={styles.line1}&gt;
          line1
        &lt;/Text&gt;
        &lt;Text style={styles.instructions}&gt;
          Press Cmd+R to reload,{&#39;\n&#39;}
          Cmd+D or shake for dev menu
        &lt;/Text&gt;
      &lt;/View&gt;

style:

    container: {
      flex: 1,
      justifyContent: &#39;center&#39;,
      alignItems: &#39;center&#39;,
      backgroundColor: &#39;#F5FCFF&#39;,
      borderWidth: 1,
      flexDirection: &#39;column&#39;,
    },
    welcome: {
      fontSize: 20,
      textAlign: &#39;center&#39;,
      margin: 10,
      borderWidth: 1,
    },
    line1: {
        backgroundColor: &#39;#FDD7E4&#39;,
    },
    instructions: {
      textAlign: &#39;center&#39;,
      color: &#39;#333333&#39;,
      marginBottom: 5,
      borderWidth: 1,
    },


Thank you!

**Update 1:**
Suggestion by Nishanth Shankar, adding 
`flex:1` for the wrapper, 
`flexDirection: &#39;row&#39;`

Output:

[![enter image description here][2]][2]

Code:

      &lt;View style={styles.container}&gt;
        &lt;View style={{flex:1}}&gt;
          &lt;Text style={styles.welcome}&gt;
            Welcome to React Natives
          &lt;/Text&gt;
        &lt;/View&gt;
        &lt;View style={{flex:1}}&gt;
          &lt;Text style={styles.line1}&gt;
            line1
          &lt;/Text&gt;
        &lt;/View&gt;
        &lt;View style={{flex:1}}&gt;
          &lt;Text style={styles.instructions}&gt;
            Press Cmd+R to reload,{&#39;\n&#39;}
            Cmd+D or shake for dev menu
          &lt;/Text&gt;
        &lt;/View&gt;
      &lt;/View&gt;

      container: {
        flex: 1,
        justifyContent: &#39;center&#39;,
        alignItems: &#39;center&#39;,
        backgroundColor: &#39;#F5FCFF&#39;,
        borderWidth: 1,
        flexDirection: &#39;row&#39;,
        flexWrap: &#39;wrap&#39;,
      },
      welcome: {
        fontSize: 20,
        textAlign: &#39;center&#39;,
        margin: 10,
        borderWidth: 1,
      },
      line1: {
          backgroundColor: &#39;#FDD7E4&#39;,
      },
      instructions: {
        textAlign: &#39;center&#39;,
        color: &#39;#333333&#39;,
        marginBottom: 5,
        borderWidth: 1,
      },


  [1]: http://i.stack.imgur.com/7LaIW.png
  [2]: http://i.stack.imgur.com/N7J8C.png

100% width in React Native Flexbox

I&#39;m making an android app using react native and I&#39;ve used TouchableOpacity component to create buttons.  
I use a text input component to accept text from the user and the button should **only be enabled** once the text input matches a certain string.  
I can think of a way to do this by initially rendering the button without the TouchableOpactiy wrapper and re-rendering with the wrapper once the input string matches.   
But I&#39;m guessing there is a much better way to do this. Can anyone help?

Disabling buttons on react native

How can I set minimum width or height for React Native component?

In css, I can use min-width/min-height

https://facebook.github.io/react-native/docs/flexbox.html#content

There is no minWidth/minHeight on react-native docs

Minimum width/height in React Native

Something similar to [NSLocale currentLocale] in Objective-C.

What&#39;s the best way to get device locale in react native (iOS)?

I would like to ask how react native handle or do the responsive font. For example in iphone 4s i Have fontSize: 14, while in iphone 6 I have fontSize: 18.

React Native Responsive Font Size

We need to keep our API server security with CORS restriction : 

    Access-Control-Allow-Origin : http://myonlinesite.com

But we also needs this API to be accessible for our mobile apps (Android+iOs).

All the solutions I found tell me to allow all origin : ```*``` , but this would be a big security failure for our API.

We are building our apps with Cordova, which WebView serves local files and therefore sends : ```origin: null``` , for all its http(s) requests. So we are thinking about adding ```null``` to the allowed origin. It&#39;s better, since it will block every other website attempting to fetch our API, but it will allow any mobile apps to fetch it...

Is there any more interesting solution for this ?

Thank you!

Content Type	Original Author	Original Content on Stackoverflow
Question	Joel	View Question on Stackoverflow
Solution 1 - Cordova	Nader Dabit	View Answer on Stackoverflow

Phone gap vs React Native

Cordova Problem Overview

Cordova Solutions

Solution 1 - Cordova

UUID or SEQUENCE for primary key?

gsl::not_null<T*> vs. std::reference_wrapper<T> vs. T&

Attributions