[英]Swift can't call protocol method via delegate
I have two classes. 我有两节课。 One class is named
ViewController
and the other class is named TabView
. 一个类名为
ViewController
,另一个类名为TabView
。
My goal is to call a function changeTab()
which is inside the TabView class from the ViewController. 我的目标是从ViewController调用TabView类内部的函数
changeTab()
。
Somehow I am having trouble with it because everytime my delegate is nil
. 我莫名其妙地遇到了麻烦,因为每次我的代表都
nil
。
Here is my code for ViewController: 这是我的ViewController代码:
protocol TabViewProtocol: class {
func changeTab()
}
class ViewController: NSViewController {
// delegate
weak var delegateCustom : TabViewProtocol?
override func viewDidLoad() {
print(delegateCustom) // outputs "nil"
}
buttonClickFunction() {
print(delegateCustom) // outputs "nil"
delegateCustom?.changeTab() // doesn't work
}
}
Here is my code for TabView: 这是我的TabView代码:
class TabView: NSTabViewController, TabViewProtocol {
let myVC = ViewController()
override func viewDidLoad() {
super.viewDidLoad()
myVC.delegateCustom = self
}
func changeTab() {
print("test succeed")
}
}
Can someone explain me what I am doing wrong? 有人可以解释我在做什么吗? - I am new to delegates and protocols...
-我是代表和协议的新手...
You are using the delegate pattern wrongly. 您错误地使用了委托模式。 It is hard to tell which controller you want to define the protocol for and which one you want to adopt it - but here is one possible way.
很难说出要为哪个控制器定义协议以及要采用哪个协议-但这是一种可能的方法。
// 1. Define your protocol in the same class file as delegate property.
protocol TabViewProtocol: class {
func changeTab()
}
// 2. Define your delegate property
class ViewController: NSViewController {
// delegate
weak var delegateCustom : TabViewProtocol?
override func viewDidLoad() {
// It should be nil as you have not set the delegate yet.
print(delegateCustom) // outputs "nil"
}
func buttonClickFunction() {
print(delegateCustom) // outputs "nil"
delegateCustom?.changeTab() // doesn't work
}
}
// 3. In the class that will use the protocol add it to the class definition statement
class TabView: NSTabViewController, TabViewProtocol {
let myVC = ViewController()
override func viewDidLoad() {
super.viewDidLoad()
myVC.delegateCustom = self
// Should output a value now
print(myVC.delegateCustom) // outputs "self"
}
func changeTab() {
print("test succeed")
}
}
you are creating a new instance in this line: 您正在此行中创建一个新实例:
let myVC = ViewController()
you should get existing instance of your ViewController.then set 您应该获取ViewController.then的现有实例
myVC.delegateCustom = self
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