Geek20 Geek20 - 11 months ago 105
Objective-C Question

Objective-C code (array.indexOfObjectPassingTest) to Swift

How can I use the Objective-C code below in Swift, I tried but something is wrong.


NSUInteger index = [theArray indexOfObjectPassingTest:
^BOOL(NSDictionary *dict, NSUInteger idx, BOOL *stop)
return [[dict objectForKey:@"name"] isEqual:theValue];

Swift (Doesn't work):

let index = theArray.indexOfObjectPassingTest { (var dict: NSDictionary, var ind: Int, var bool: Bool) -> Bool in
return dict.objectForKey("name")?.isEqual("theValue")

Answer Source

I played with it and got this to work:

let theArray: NSArray = [["name": "theName"], ["name": "theStreet"], ["name": "theValue"]]

let index = theArray.indexOfObjectPassingTest { (dict, ind, bool) in return dict["name"] as? String == "theValue" }

if index == NSNotFound {
    print("not found")
} else {
    print(index)    // prints "2"

This can be further reduced. As @newacct mentioned in the comment, the return can be dropped since the closure is only a single line. Also, _ can be used in place of the parameters that aren't being used:

let index = theArray.indexOfObjectPassingTest { (dict, _, _) in dict["name"] as? String == "theValue" }

You can get rid of the parameter list in the closure entirely and use the default $0 value. Note in that case, the three parameters are combined as a tuple, so the first value of the tuple dict is referenced as $0.0:

let index = theArray.indexOfObjectPassingTest { $0.0["name"] as? String == "theValue" }