How to get an object index from an array in swift

Question

I am creating a class in swift work as a container of a set of protocols. Below is the source code. The KeyValueObserverDelegate protocol is added in KeyValueObserverService class by addObserver() method. The problem happens on removeObserver() method, the line is index = array.indexOf($0 == observer).

I got an error:

anonymous closure argument not contained in a closure.

I don't know what wrong with my class. How can I get the index of an object from an array?

class KeyValueObserverService{

    private var observerList:Dictionary<String, [KeyValueObserverDelegate]> = Dictionary()

    func addObserver(key:String, observer:KeyValueObserverDelegate){
        var array:Array<KeyValueObserverDelegate>?
        if observerList.keys.contains(key){
            array = observerList[key]
        } else {
            array = Array<KeyValueObserverDelegate>()
            self.observerList[key] = array
        }
        array?.append(observer)
    }

    func updateValueForKey(key:String, value:AnyObject?){
        let array = self.observerList[key];
        if array == nil{
            return
        }
        for  element in array!{
            element.valueChanged(value)
        }
    }

    func removeObserver(key:String, observer:KeyValueObserverDelegate){
        if self.observerList.keys.contains(key) == false{
            return
        }
        var array:[KeyValueObserverDelegate] = self.observerList[key]!;

        let index:Int?


        index = array.indexOf($0 == observer)

        array.removeAtIndex(index!)
    }
}

protocol KeyValueObserverDelegate :class{
    func valueChanged(value:AnyObject?)
}

vadian · Accepted Answer · 2016-03-23 11:43:36Z

1

Read the error message carefully

...not contained in a closure

By definition a closure is enclosed in a pair of curly braces

array.indexOf({$0 == observer})

or with trailing closure syntax

array.indexOf{$0 == observer}

Edit:

Since a protocol does not conform to Equatable by default use the identity operator

array.indexOf{$0 === observer}

edited Mar 23, 2016 at 11:43

answered Mar 23, 2016 at 8:32

vadian

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5 Comments

Joey Yi Zhao Over a year ago

Thanks for correcting me. After make this change, the error message becomes "Binary operator "==" cannot be applied to "KeyValueObserverDelegate" operands.

vadian Over a year ago

KeyValueObserverDelegate seems to be a custom type. You need to make the type conform to the Equatable protocol by implementing the == operator.

Joey Yi Zhao Over a year ago

KeyValueObserverDelegate is defined as a protocol, it is located at the bottom of my post. How can I conform to Equatable?

Joey Yi Zhao Over a year ago

KeyValueObserverDelegate is defined as a protocol, it is located at the bottom of my post. When I add Equable, my code will report a lot errors. Most of them are "KeyValueObserverDelegate can only be used as a generic constraint"

vadian Over a year ago

Either use the identity operator (===) or add an identifier property or something else unique to the protocol to be able to identify the particular observer. I edited the answer.

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