Convert Unmanaged<AnyObject>! to Bool in Swift

Question

I am trying to get the result of a method of an existing Objective C class, called using performSelector

let result = controlDelegate.performSelector("methodThatReturnsBOOL") as? Bool

I need to cast this result to Bool type of Swift.

The code mentioned above, gives a warning

"Cast from 'Unmanaged!' to unrelated type 'Bool' always fails"

and the result is always "false", even when the method returns YES.

Any suggestions for converting the result to Bool ?

Signature for methodThatReturnsBOOL

- (BOOL)methodThatReturnsBOOL
{
    return YES;
}

Answer 1

It's been a long time since this has remained unanswered so I'm adding what I have learned along the way.

To convert a BOOL value returned by an Objective C method you can simply cast it using,

if let result = controlDelegate.performSelector("methodThatReturnsBOOL") {
    print("true")
} else {
    print("false")
}

Here you can also assign the value true/false to a Swift Bool, if required.

Note : I tried casting Unmanaged<AnyObject> directly to Bool using takeRetainedValue() as suggested by many answers on SO, but that doesn't seem to work in this scenario.

Answer 2

This is the solution in Swift 3, as the methods are a bit different. This method also checks if Objective-C object responds to selector, to avoid crashing.

import ObjectiveC

let selector = NSSelectorFromString("methodThatReturnsBOOL")

guard controlDelegate.responds(to: selector) else {
    return
}

if let result = controlDelegate.perform(selector) {
    print("true")
}
else {
    print("false")
}