Swift - protocol as type as target of button action

问题

I am trying to create - HeaderView which is subclass of UIView, it contains a close button and a title label.

class HeaderView: UIView {
    private var titleLabel: UILabel!
    private var closeButton: UIButton!
}

I don't want to add self as target of closeButton action but want to set myViewController as its target, moreover I want HeaderView class to be reusable.

So I declared a protocol:

protocol CloseViewProtocol {
    func closeViewAction(sender: UIButton!)
}

And declared a variable like this:

class HeaderView: UIView {
    private var titleLabel: UILabel!
    private var closeButton: UIButton!

    var closeButtonTarget: CloseViewProtocol?
}

to enforce (at compile time) that closeButtonTarget implements closeViewAction: method.

Now I can't do this:

closeButton.addTarget(closeButtonTarget, action: "closeViewAction:", forControlEvents: .TouchUpInside)

doing which compiler complains -

Cannot convert value of type 'CloseViewProtocol?' to expected argument type 'AnyObject?'

To resolve this I can do this:

let buttonTarget = closeButtonTarget as! UIViewController
closeButton.addTarget(buttonTarget, action: "closeViewAction:", forControlEvents: .TouchUpInside)

Is there any better way to achieve expected behavior?

回答1:

I like Andrius approach, but to answer the question, you have to add the class keyword to your protocol’s inheritance list:

protocol CloseViewProtocol: class {
    func closeViewAction(sender: UIButton!)
}

回答2:

This is a bit old school - protocol delegate, new patterns are more functional programming I would suggest using closures

var closeHanlder:()->Void?

Then have button as private var inside, and in View Controller do

headerViewInstance.closeHandler = self.handleCloseFunction

I should add that the button action gets handled in the headerView, whose action does what it needs and calls closeHandler?()

来源：https://stackoverflow.com/questions/32760481/swift-protocol-as-type-as-target-of-button-action

标签

swift

uibutton

protocols