swift：将存储的属性用作计算属性是正确的 [英] swift: Is correct to use stored properties as computed properties

问题描述

我试图实现这个目标-c代码

I'm try to achieve this objective-c code

@property (strong) UIView *customView;

-(UIView*)customView
{
   if (!customView){
       self.customView = [[UIView alloc]init];
       self.customView.backgroundColor = [UIColor blueColor];
  }
   return customView;
}

为什么我要用它？从很多地方调用customView，所以我们必须在所有地方检查这个条件。为了避免这种重复，我写了这个。

Why am I use this? customView called from many place, so we have to check this condition in all place. To avoid this duplication, I wrote this.

所以我尝试创建存储的属性，并使用getter方法检查是否已创建。

So I'm try to create stored properties and also use getter method to check if already either created or not.

var mainView : UIView? {

  get{
   if let customView = self.mainView{
        return self.mainView
   }
   var customView : UIView = UIView() 
   self.mainView = customView
   self.mainView.backgroundColor = UIColor(blueColor)
   return customView 
 }
 set{
  self.mainView = newValue
  }
}

这是正确的吗？或其他任何方法吗？

Is this correct? or any other approach to do this?

注意：以上代码没有任何警告或错误。但与存储和计算属性混淆。请让我说清楚。

Note: There's no warning or error with above code. But confusion with stored and computed properties. Please make me clear.

推荐答案

不确定原因，但是懒惰的变量与计算属性相结合会导致错误：

Not sure why, but lazy variables combined with computed properties result in an error:

'lazy' attribute may not be used on a computed property

但这似乎有效：

class MyClass {
  @lazy var customView: NSView = {
    let view = NSView()
    // customize view
    return view
  }()
}

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