The [syntax for function types][1] is `(in) -&gt; out`.

    typealias CompletionBlock = (NSString?) -&gt; Void
    // or
    typealias CompletionBlock = (result: NSData?, error: NSError?) -&gt; Void

&lt;!----&gt;

    var completion: CompletionBlock = { reason in print(reason) }
    var completion: CompletionBlock = { result, error in print(error) }

Note that the parentheses around the input type are only required as of Swift 3+.


  [1]: https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Functions.html

[Here](http://fuckingclosuresyntax.com/) is awesome blog about swift closure. 

Here are some examples:

As a variable:

    var closureName: (inputTypes) -&gt; (outputType)

As an optional variable:

    var closureName: ((inputTypes) -&gt; (outputType))?

As a type alias:

    typealias closureType = (inputTypes) -&gt; (outputType)

I&#39;m trying to join all the tests from multiple files in one file, something like this:

      describe(&#39;Controllers&#39;, function() {
        describe(&#39;messages.js&#39;, function() {
          require(&#39;./controllertests/messages&#39;).test(options);
        })
        describe(&#39;users.js&#39;, function() {
          require(&#39;./controllertests/users&#39;).test(options);
        })
      })

I&#39;m pretty sure this is not the best way to join tests, I&#39;m having some dificulty finding examples of how to do this :s

joining tests from multiple files with mocha.js

Consider the two classes:

    class A {
    	var x: Int
    	
    	init(x: Int) {
    		self.x = x
    	}
    	
    	convenience init() {
    		self.init(x: 0)
    	}
    }
    
    class B: A {
    	init() {
    		super.init() // Error: Must call a designated initializer of the superclass &#39;A&#39;
    	}
    }

I don&#39;t see why this isn&#39;t allowed. Ultimately, each class&#39;s designated initializer is called with any values they need, so why do I need to repeat myself in `B`&#39;s `init` by specifying a default value for `x` again, when the convenience `init` in `A` will do just fine?

Why can&#39;t Swift initializers call convenience initializers on their superclass?

We can declare block as below in Objective-C.

    typedef void (^CompletionBlock) (NSString* completionReason);

I&#39;m trying to do this in swift, it give error.

    func completionFunction(NSString* completionReason){ }
    typealias CompletionBlock = completionFunction

&gt; Error : Use of undeclared &#39;completionFunction&#39;

Definition :

    var completion: CompletionBlock = { }

How to do this? 

**Update:** 

According to @jtbandes&#39;s answer, I can create closure with multiple arguments as like

    typealias CompletionBlock = ( completionName : NSString, flag : Int) -&gt; ()

swift : Closure declaration as like block declaration

We can declare block as below in Objective-C.
<pre><code class="hljs language-objectivec">typedef void (^CompletionBlock) (NSString* completionReason);
</code></pre>
I'm trying to do this in swift, it give error.
<pre><code class="hljs language-swift">func completionFunction(NSString* completionReason){ }
typealias CompletionBlock = completionFunction
</code></pre>
> Error : Use of undeclared 'completionFunction'
Definition :
<pre><code class="hljs language-css">var completion: CompletionBlock = { }
</code></pre>
How to do this?
Update:
According to @jtbandes's answer, I can create closure with multiple arguments as like
<pre><code class="hljs language-ini">typealias CompletionBlock = ( completionName : NSString, flag : Int) -> ()
</code></pre>

I have a `UILabel` named `titleLabel` in my **storyboard** nib set to its default height. I want it to *programatically* expand in height to fit it&#39;s content. Here is what I have tried so far:
    
    // just setting content
    titleLabel.text = &quot;You don&#39;t always know what you are getting with mass-market cloud computing services. But with SimpliCompute, the picture is clear. SimpliCompute gives you powerful virtual servers you can deploy using just your web browser. That’s enterprise grade technology you can deploy and control on-the-fly.&quot;
    
    titleLabel.numberOfLines = 0
       
    titleLabel.preferredMaxLayoutWidth = 700

    titleLabel.lineBreakMode = NSLineBreakMode.ByWordWrapping

    titleLabel.sizeToFit()

None of this works for me in any combination! I always only see one line of text in my `UILabel`. What am I doing wrong?

I absolutely need the text content to be variable.

How do I set adaptive multiline UILabel text?

I&#39;m trying to convert my app to the Swift language.

I have this line of code:

    [[UIBarButtonItem appearanceWhenContainedIn:[UINavigationBar class], nil]
                         setTitleTextAttributes:textDictionary
                                       forState:UIControlStateNormal];

How to convert it to Swift?

In [Apple&#39;s docs][1], there is no such method.

  [1]: https://developer.apple.com/library/prerelease/ios/documentation/UIKit/Reference/UIAppearance_Protocol/index.html#//apple_ref/occ/intfcm/UIAppearance

appearanceWhenContainedIn in Swift

I&#39;m looking for behavior similar to Objective-C&#39;s `+(void)initialize` class method, in that the method is called once when the class is initialized, and never again thereafter.

A simple `class init () {}` in a `class` closure would be really sleek! And obviously when we get to use &quot;`class var`s&quot; instead of &quot;`static var`s in a struct closure&quot;, this will all match really well!

&quot;initialize&quot; class method for classes in Swift?

How would I get the hour of the day in Swift.
I have tried `NSCalendar` and `NSDateComponents`, but I&#39;m afraid I&#39;m just starting with Swift.

How to get the hour of the day with Swift?

Is there any way to hide suggestions list above keyboard? I couldn&#39;t find any solution in documentation.

iOS 8 - How to hide suggestion list above keyboard?

I always thought functions and methods were the same, until I was learning Swift through the &quot;Swift Programming Language&quot; eBook. I found out that I cannot use `greet(&quot;John&quot;, &quot;Tuesday&quot;)` to call a function that I declared inside a class, as shown in the eBook in the screen shot below:

![function declaration in swift][1]

I received a error saying that &quot;**Missing argument label &#39;day:&#39; in call**&quot; as per this screen shot:

![Error message in swift][2]

Here is the code:-

    import Foundation
    import UIKit
    
    class ViewController2: UIViewController {
        override func viewDidLoad() {
            super.viewDidLoad()
            
            //var dailyStatement = greet(&quot;John&quot;, &quot;Tuesday&quot;)
            var dailyStatement = greet(&quot;John&quot;, day: &quot;Tuesday&quot;)
            println(dailyStatement)
        }
    
        func greet(name: String, day: String) -&gt; String {
            return &quot;Hello \(name), today is \(day).&quot;
        }
    }


  [1]: http://i.stack.imgur.com/qPXcE.png
  [2]: http://i.stack.imgur.com/DJBrB.png

After some research, I found this post: https://stackoverflow.com/questions/155609/what-is-the-difference-between-a-method-and-a-function, and it seems to me that the function that I declared inside a class is actually called a method. So, the syntax that I use to call the method is different compared to the syntax that I use to call a function. 

I never realized this difference when I was programming in Objective-C. 

1. What are the differences between functions and methods in Swift?

2. When do we use functions and when do we use methods in Swift?

What are the differences between functions and methods in Swift?

The documentation says

&gt; NOTE
&gt; 
&gt; Swift classes do not inherit from a universal base class. Classes you
&gt; define without specifying a superclass automatically become base
&gt; classes for you to build upon.”
&gt; 
&gt; Excerpt From: Apple Inc. “[The Swift Programming Language.](https://itun.es/at/jEUH0.l)” iBooks.

It doesn&#39;t make much sense to me. There is a reason why Objective-C has a universal base class, and the same reason should apply to Swift, does it? `NSObject` manages retain/release semantics, a default implementation for `isEqual:`, `hash` and `description`. All this functionality is available in Swift too.

(Objective-C and Swift use the same runtime...)

So, what&#39;s up with that? Are Swift classes with no defined superclasses just `NSObject`s that pose as proper root classes under the hood? Or is the default object-behaviour duplicated for each new root-class? Or have they created another Swift-baseclass? The implementation of `retain` and `release` is really complex, because it needs to take multithreading and weak references into account at the same time.

Is there maybe a universal base class in Swift (despite what the documentation says)? It would be really handy, because in Objective-C I can e.g. write extensions that let me coalesce method invocations to the main runloop like `[obj.eventually updateCounter]` which can be read as &quot;call `-updateCounter` the next time the main runloop gets in control. If, in the meantime, I call this method again, it should be called only once anyways. With this extension one could implement `-[UIView setNeedsDisplay]` as `[self.eventually display];` This is no longer possible in Swift if there is no universal base class (or maybe it is, who knows?)

Content Type	Original Author	Original Content on Stackoverflow
Question	Mani	View Question on Stackoverflow
Solution 1 - Ios	jtbandes	View Answer on Stackoverflow
Solution 2 - Ios	BLC	View Answer on Stackoverflow

swift : Closure declaration as like block declaration

Ios Problem Overview

Ios Solutions

Solution 1 - Ios

Solution 2 - Ios

Why can't Swift initializers call convenience initializers on their superclass?

joining tests from multiple files with mocha.js

Attributions