Clever Geek Handbook

Completion Handlers in Swift

I'm new to rapid development and am trying to get information about closures and completion handlers. I have a function with the following declaration inside a structure called ObjectData p>

func getData(id1:Int, id2:Int, completion: (dataObject? -> Void))

I am trying to call this function like

ObjectData.getData(1, id2: 2){
    (let myObject) in
}

but I am getting the following error:

Cannot call 'getData' with argument list like '(NSNumber, id2: NSNumber, (_) -> _)'

Please help someone help

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4 answers


For better readability, change the title to this. Remember, you need to declare types, not variable names:

func getData(id1:Int, id2:Int, completion: (ObjectData?) -> (Void))

I now use this syntax to use closures:



self.getData(1, id2: 1) { (data) -> (Void) in

     // Some code executed in closure
}

If you'd like to explore further, you can find the complete syntax for closures here (note the corresponding website name). Hope this helps!

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Away from my Mac now, so I can't check, but try this:

ObjectData.getData(1, id2: 2, (dataObject) -> { 
...code...
});


Also can't check now, but I think this should work as well:

    ObjectData.getData(1, id2: 2)(dataObject){ 
...code...
}
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try to initialize your class first (e.g. var objectData = ObjectData ()) and then call the function with objectData.getData ... it should work just like this.

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In SWIFT 3, it is known as the completion of the close.

func getData(id1:Int, id2:Int, completion:@escaping(dataObject?) -> (Void)) {

    //Do the stuff before calling completion closure
    completion(value as? dataObject)   
}

ObjectData.getData(id1:1, id2: 2,completion:{(data) -> (Void) in
    //Do the completion stuff here
}
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