Swift中的可選閉包4

Question

我需要一個按需執行的閉包方法。

在斯威夫特3我以前做這樣的事情：

// Declare closure 
var checksPerformed: ((Void) -> Void)? // Declaration 

// Call when needed 
checksPerformed?() 

//Only executes when checksPerformed is called 
checksPerformed = { _ in 
    // do stuff here 
} 

在斯威夫特4這不再是這種情況。

和固定這樣的警告後沒有像以前一樣工作。 這樣做的新方法是什麼？

如果我更新聲明：var checksPerformed: (() ->())?我越來越

Answer 1

Distinguish between single-tuple and multiple-argument function types

// Declare closure 
var checksPerformed: (() ->())? // Declaration 

// Call when needed 
checksPerformed?() 

//Only executes when checksPerformed is called 
checksPerformed = { 
    // do stuff here 
} 

Answer 2

使用

var checksPerformed: (()->(Void))? 

如果你這樣做，一切都應該按預期工作。

不要分配關閉時使用_在：

//Only executes when checksPerformed is called 
checksPerformed = { 
    // do stuff here 
} 

//Call when needed 
checksPerformed?()