ViewController.Type 没有名为的成员 [英] ViewController.Type does not have a member named

问题描述

只是一个简单的任务，但我遇到了麻烦.尝试另辟蹊径，但失败了.

Just a simple task, but I'm in trouble. Trying to make a different way but it fails.

如何使用先前声明的变量初始化 NSTimer?var 和 let 都没有帮助.

How to init NSTimer with declared previously variable? Neither var nor let helps.

推荐答案

属性的初始值(在您的情况下:timer)不能依赖于该类的另一个属性(在您的情况下:间隔).

The initial value of a property (in your case: timer) cannot depend on another property of the class (in your case: interval).

因此你必须将赋值 timer = NSTimer(interval, ...) 移动到一个 method类，例如进入 viewDidLoad.因此，timer 必须定义为可选或隐式解包可选.

Therefore you have to move the assigment timer = NSTimer(interval, ...) into a method of the class, e.g. into viewDidLoad. As a consequence, timer has to be defined as an optional or implicitly unwrapped optional.

还要注意 Selector(...) 将文字 string 作为参数，而不是方法本身.

Note also that Selector(...) takes a literal string as argument, not the method itself.

所以这应该有效:

class ViewController: UIViewController {

    var interval : NSTimeInterval = 1.0
    var timer : NSTimer!

    func timerRedraw() {

    }

    override func viewDidLoad() {
        super.viewDidLoad()
        timer = NSTimer(timeInterval: interval, target: self, selector: Selector("timerRedraw"), userInfo: nil, repeats: true)

        // ...
    }

    // Other methods ...
}

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