How to write a generic apply() function in Swift?

Question

Is there any way to get the following working in Swift 3?

 let button = UIButton().apply {
        $0.setImage(UIImage(named: \"UserLocation\"), for: .normal         


        

Answer 1

The HasApply protocol

First of all lets define the HasApply protocol

protocol HasApply { }

and related extension

extension HasApply {
    func apply(closure:(Self) -> ()) -> Self {
        closure(self)
        return self
    }
}

Next let make NSObject conform to HasApply.

extension NSObject: HasApply { }

That's it

Let's test it

let button = UIButton().apply {
    $0.titleLabel?.text = "Tap me"
}

print(button.titleLabel?.text) // Optional("Tap me")

Considerations

I wouldn't use NSObject (it's part of the Objective-C way of doing things and I assume it will be removed at some point in the future). I would prefer something like UIView instead.

extension UIView: HasApply { }