It is called nil coalescing operator. If `highs` is not `nil` than it is unwrapped and the value returned. If it is nil then `[ChartHighlight]()` returned. It is a way to give a default value when an optional is `nil`.

I want to describe with JSON schema array, which should consist of zero or more predefined values. To make it simple, let&#39;s have these possible values: `one`, `two` and `three`. 

Correct arrays (should pass validation):

    []
    [&quot;one&quot;, &quot;one&quot;]
    [&quot;one&quot;, &quot;three&quot;]

Incorrect:

    [&quot;four&quot;]

Now, I know the `&quot;enum&quot;` property should be used, but I can&#39;t find relevant information where to put it.

Option A (under `&quot;items&quot;`):
    
    {
        &quot;type&quot;: &quot;array&quot;,
        &quot;items&quot;: {
            &quot;type&quot;: &quot;string&quot;,
            &quot;enum&quot;: [&quot;one&quot;, &quot;two&quot;, &quot;three&quot;]
        }
    }

Option B:

    {
        &quot;type&quot;: &quot;array&quot;,
        &quot;items&quot;: {
            &quot;type&quot;: &quot;string&quot;
        },
        &quot;enum&quot;: [&quot;one&quot;, &quot;two&quot;, &quot;three&quot;]
    }

Correct way to define array of enums in JSON schema

In MVC 5, I had the following extension methods to generate absolute URLs, instead of relative ones:

    public static class UrlHelperExtensions
    {
        public static string AbsoluteAction(
            this UrlHelper url,
            string actionName, 
            string controllerName, 
            object routeValues = null)
        {
            string scheme = url.RequestContext.HttpContext.Request.Url.Scheme;
            return url.Action(actionName, controllerName, routeValues, scheme);
        }
    
        public static string AbsoluteContent(
            this UrlHelper url,
            string contentPath)
        {
            return new Uri(url.RequestContext.HttpContext.Request.Url, url.Content(contentPath)).ToString();
        }
    
        public static string AbsoluteRouteUrl(
            this UrlHelper url,
            string routeName,
            object routeValues = null)
        {
            string scheme = url.RequestContext.HttpContext.Request.Url.Scheme;
            return url.RouteUrl(routeName, routeValues, scheme);
        }
    }

What would the equivalent be in ASP.NET Core?

 - `UrlHelper.RequestContext` no longer exists.
 - You can&#39;t get hold of the `HttpContext` as there is no longer a static `HttpContext.Current` property.

As far as I can see, you would now require the `HttpContext` or `HttpRequest` objects to be passed in also. Am I right? Is there some way to get hold of the current request?

Am I even on the right track, should the domain now be an environment variable, which is simple appended to the relative URL? Would this be a better approach?

Getting absolute URLs using ASP.NET Core

I have seen such function:

    public func highlightValues(highs: [ChartHighlight]?)
    {
        // set the indices to highlight
        _indicesToHightlight = highs ?? [ChartHighlight]();

        // redraw the chart
        setNeedsDisplay();
    }

What&#39;s the purpose of `??` here? I searched, but it seems searching `??` is hard to find a proper answer.

what&#39;s the purpose of double question mark in swift

I have seen such function:
<pre><code class="hljs language-scss">public func highlightValues(highs: [ChartHighlight]?)
{
 // set the indices to highlight
 _indicesToHightlight = highs ?? [ChartHighlight]();

 // redraw the chart
 setNeedsDisplay();
}
</code></pre>
What's the purpose of <code>??</code> here? I searched, but it seems searching <code>??</code> is hard to find a proper answer.

I don&#39;t use a storyboard/xib for launch screen and get these errors in Xcode7+.
    
    - All interface orientations must be supported unless the app requires full screen.

    - A launch storyboard or xib must be provided unless the app requires full screen.



A launch storyboard or xib must be provided unless the app requires full screen

When Apple&#39;s official iOS Messages app is open and in the foreground, new messages from other contacts trigger a stock, native iOS notification alert banner. See image below.

Is this possible in 3rd party apps on the App Store? Local and/or Push Notifications for your app while your app is **open and in the foreground**?

When testing **my app**, notifications are received but **no iOS alert UI is shown**.

But this behavior **is** seen in Apple&#39;s official Messages app:

![Messages is open and in the foreground. Still shows a notification alert.][1]

The [Local and Remote Notification Programming Guide](https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/IPhoneOSClientImp.html) says:

 &gt; When the operating system delivers a local notification or remote notification and the target app is **not running in the foreground**, it can present the notification to the user through an **alert**, icon badge number, or sound.
 &gt;
 &gt; If the app is running in the **foreground** when the notification is delivered, the app delegate receives a local or remote notification.

So yes, we can receive the *notification data* while in the foreground. But I see no way to **present the native iOS notification alert UI**.

    -(void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo 
    {
        // I know we still receive the notification `userInfo` payload in the foreground.
        // This question is about displaying the stock iOS notification alert UI.

        // Yes, one *could* use a 3rd party toast alert framework. 
        [self use3rdPartyToastAlertFrameworkFromGithub]
    }

Is Messages then using a private API to display the alert while in the foreground?

For the purpose of this question, **please do not suggest any 3rd party &quot;toast&quot; pop-up alerts** on github or etc. I&#39;m only interested if this can be done using the **stock, native iOS** Local or Push Notification alerts UI *while your application is open and in the foreground*.


  [1]: http://i.stack.imgur.com/gwFJql.jpg

Displaying a stock iOS notification banner when your app is open and in the foreground?

Getting this error in Swift 2.0.

&gt; Binary operator &#39;|&#39; cannot be applied to two UIViewAutoresizing operands

Here is the code:

    let view = UIView(frame: CGRect(x: 0, y: 0, width: 320, height: 568))
    addSubview(view)
    view.autoresizingMask = UIViewAutoresizing.FlexibleWidth | UIViewAutoresizing.FlexibleHeight

Any idea what can be the problem?
![enter image description here][1]


  [1]: http://i.stack.imgur.com/xVzxK.png

Binary operator &#39;|&#39; cannot be applied to two UIViewAutoresizing operands

Recently i downloaded xcode 7 beta and facing the error:

-fembed-bitcode is not supported on versions of iOS prior to 6.0

Is there any work around to fix this issue with out changing deployment target?

Thanks in advance.



-fembed-bitcode is not supported on versions of iOS prior to 6.0

I got an email that my latest binary submission to Apple for an iOS/Watch OS app was invalid due to:

&gt; The app links to non-public libraries in PlugIns/iPrayed.appex/iPrayed
&gt; WatchKit App.app/_WatchKitStub/WK:
&gt; /System/Library/PrivateFrameworks/SockPuppetGizmo.framework/SockPuppetGizmo

I have submitted this build before without any issues, and only made a couple of changes to a few lines of code, without adding anything at all.  Any clue what this is about?

Non-Public Library SockPuppetGizmo

I want to be able to increment a counter atomically and I can&#39;t find any reference on how to do it. 

Adding more information based on comments:

   - Are you using GCD? No. I am not using GCD. Having to use a queue system to increment a number seems overkill.
   - _Do_ You understand basic thread safety? Yes I do otherwise I would not be asking about atomic increments.
   - Is this variable local? No. 
   - _Is it instance level?_ Yes it should be part of a single instance.

I want to do  something like this:

     class Counter {
          private var mux: Mutex
          private (set) value: Int
          func increment() {
              mux.lock()
              value += 1
              mux.unlock()
          }
     }


How do I atomically increment a variable in Swift?

I&#39;m going through the iOS tutorial from [Apple developer page][1].


  [1]: https://developer.apple.com/library/prerelease/ios/referencelibrary/GettingStarted/DevelopiOSAppsSwift/Lesson1.html#//apple_ref/doc/uid/TP40015214-CH3-SW1

It seems to me that `protocol` and `interface` almost have the same functionality.
 

 - Are there any differences between the two?
 
 - the different usage in the project?

 
**Updated** 

**Yes**, I did read the link above and I&#39;m still not sure what the differences and usage between `protocol` and `interface`. When I ask a question like this, I would like to see a simple explanation about the topic. Sometime it could be tough to get everything from the documentation.

Compare Protocol in Swift vs Interface in Java

In swift 2.0, `print()` automatically adds a newline character. In swift 1.2, `println()` and `print()` used to be separate functions. So how do I print some text and not add a newline to it since swift no longer has a print function that does not append newlines. 


print without newline in swift

I updated my project to Swift 2, and received a bunch of `redundant conformance of XXX to protocol YYY`. This happens especially often (or always) when a class conforms to `CustomStringConvertible`. Also some place with `Equatable`.

    class GraphFeatureNumbersetRange: GraphFeature, CustomStringConvertible { // &lt;--- get the error here
    ...
    }

I suspect that I don&#39;t need to explicitly conform to a protocol when I implement `var description: String { get }`, or whatever methods the protocol requires. Should I just follow fixit instructions and remove all these? Does Swift now automatically infer the conformance if a class implements all the protocol&#39;s methods?


Content Type	Original Author	Original Content on Stackoverflow
Question	Wingzero	View Question on Stackoverflow
Solution 1 - Ios	mustafa	View Answer on Stackoverflow

what's the purpose of double question mark in swift

Ios Problem Overview

Ios Solutions

Solution 1 - Ios

Getting absolute URLs using ASP.NET Core

Correct way to define array of enums in JSON schema

Attributions