Swift: How to use instanceType in callback closure

Question

I want to pass self as instancetype to the callback closure of this function:

extension UIView {
    public func onTap(_ handler: @escaping (_ gesture: UITapGestureRecognizer, _ view: Self) -> Void) -> UITapGestureRecognizer {
        ...
    }
}

let view = UIView.init()
view.onTap { tap, v in
    ...
}

But I got an error:

Self' is only available in a protocol or as the result of a method in a class; did you mean 'UIView'?

How can I do this?

holex · Accepted Answer · 2018-02-01 13:04:09Z

1

that is just the perfect scenario (by book) when you can use protocols and extensions in Swift quite efficiently:

protocol Tappable { }

extension Tappable { // or alternatively: extension Tappable where Self: UIView {
    func onTap(_ handler: @escaping (UITapGestureRecognizer, Self) -> Void) -> UITapGestureRecognizer {
        return UITapGestureRecognizer() // as default to make this snippet sane
    }
}

extension UIView: Tappable { }

then for e.g.:

let button = UIButton.init()
button.onTap { tap, v in
    // v is UIButton...
}

while for e.g.:

let label = UILabel.init()
label.onTap { tap, v in
    // v is UILabel...
}

etc...

NOTE: you can read more about Extensions or the Protocols in the Swift Programming Language Book from Apple.

edited Feb 1, 2018 at 13:04

answered Feb 1, 2018 at 11:25

holex

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