在#selector Swift 2.2中传递参数

Question

I have a method:

func followUnfollow(followIcon: UIImageView, channelId: String) {
    let followUnfollow = followIcon
    let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(self.followIconTapped(_:)))
    followUnfollow.userInteractionEnabled = true
    followUnfollow.addGestureRecognizer(tapGestureRecognizer)
}

And also I have a method:

func followIconTapped(sender: UITapGestureRecognizer) {
    ...
}

And it's work all right. But I need to pass on channelId to followIconTapped() method.

I try this:

func followUnfollow(followIcon: UIImageView, channelId: String) {
    ...
    let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(self.followIconTapped(_:channelId)))
    ...
}

and then I try catch it:

func followIconTapped(sender: UITapGestureRecognizer, channelId: String) {
    ...
}

xCode say that channelId will never used. Why? When I build project I haven't any issue. But app is crash if I tap on followIcon .

Please, can you give me advice how to pass on channelId to followIconTapped()

Answer 1

creating a generic UITapGestureRecognizer instead use this:

class CustomTapGestureRecognizer: UITapGestureRecognizer {
    var channelId: String?
}

also use this:

override func viewDidLoad() {
    super.viewDidLoad()

    let gestureRecognizer = CustomTapGestureRecognizer(target: self, action: #selector(tapped(_:))
    gestureRecognizer.channelId = "Your string"
    view1.addGestureRecognizer(gestureRecognizer)
}

func tapped(gestureRecognizer: CustomTapGestureRecognizer) {
    if let channelId = gestureRecognizer.channelId {
        //print
    }
}

Answer 2

尝试为tapGestureRecognizer设置标签，并根据标签定义channelId 。

Answer 3

You cannot pass extra arguments to your method when you are using Selector . UITapGestureRecognizer can handle methods with signatures:

• private dynamic func handleTap() { ... }
• private dynamic func handleTapOn(gestureRecognizer: UIGestureRecognizer) { ... }

Selectors in swift aren't validate in other way then check syntactics. Thats why there is no error connected with method signature you pass to action method.

If you like use channelId in your handleTap method you have to keep your variable in some place. You can create property in your class and store there your variable to use in handleTap method.

class YourClass: BaseClass {

    // MARK: - Properties

    private var channellId: String? = nil 

    // MARK: - API

    func followUnfollow(followIcon: UIImageView, channelId: String) {
        self.channelId = channelId
        let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(handleTapOn(_:)))
    }

    // MARK: - Callbacks

    private dynamic func handleTapOn(recognizer: UIGestureRecognizer) {
        if let channelId = self.channelId {
            // Do sth
        }
    }

}