Using block in swift

Question

I'm recently started working on swift. Here i'm facing the problem with blocks so please help to do this.

Class 1:

I'm using block in Objective-C like this:

typedef void (^AHServicesCallsWrapperBlock)(id, NSError *);

declaration of block variable:

@property (nonatomic, copy) AHServicesCallsWrapperBlock webServiceWrapperBlockHandler;

and passing block a value

self.webServiceWrapperBlockHandler([graphData objectForKey:@"data"], nil);

In Class 2: And i'm using this block in another view controller like:

AHServiceCallWrapper *webServicesCallsWrapper = [[AHServiceCallWrapper alloc] init];
webServicesCallsWrapper.webServiceWrapperBlockHandler = ^(id response, NSError *error)
{
     // do stuff
}

so how can we do this in swift...

look up closures in swift. there are quite a good amount of tutorials and explanations around. Closures are the equivalent to blocks in swift. google.com.au/… — Nick Red
– Nick Red, Commented Nov 5, 2015 at 5:27
how should i do using closures, i search lots of about but not getting properly — pritam
– pritam, Commented Nov 5, 2015 at 5:29

deoKasuhal · Accepted Answer · 2015-11-05 06:01:32Z

You can use closure in Swift, Closures are self-contained blocks of functionality that can be passed around and used in your code. Closures in Swift are similar to blocks in C and Objective-C.

Closure expression syntax has the following general form:

{ (parameters) -> return type in
    statements
}

Example :

If you need to define any closure as object in class like as below,

class AHServiceCallWrapper {
  var completionBlock: ((AnyObject, NSError) -> Void)? = nil

  func doSomeStuff() {
    var json = [AnyObject]()
    var error : NSError? = nil
    //Do some stuff if completed
     if let completionBlock = self.completionBlock {
            completionBlock(json, error);
     }
  }
}

Now, you can use the implementation like

let serviceCall = AHServiceCallWrapper()
serviceCall.completionBlock =  { (response, error) -> Void in
        //Do the stuff on completion 
    }
serviceCall.doSomeStuff()

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