相当于懒惰的属性获取器的Swift [英] Swift equivalent of lazy Property getter

问题描述

以下表达式的Swift等效项是什么:

What is the Swift equivalent of the following expression:

@property (strong, nonatomic) UIView *topView;

- (UIView *)topView {
...
}

是以下内容:

var topView: UIView {
  get {
    ...
  }
}

如果前者为真，是否有办法定义外部吸气剂?

If the former is true, is there a way to define an external getter?

推荐答案

我认为您要问的是如何实现类似于以下内容的东西:

I think what you're asking is how to implement something similar to the following:

@property (nonatomic, strong) UIView *topView

- (UIView *)topView {
    if (_topView == nil) {
        _topView = //...
        // configure _topView...
    }
    return _topView;
}

这个懒惰的属性获取器很容易在Swift中实现:

This lazy property getter is easy to achieve in Swift:

lazy var topView: UIView = {
    let view = //...
    // configure view...
    return view
}()

这将导致一个只读变量，该变量仅在首次访问时才初始化.您发布的Swift代码是计算所得的只读属性，每次访问该属性都会对其进行评估.

This results in a read-only variable that is initialised only when first accessed. The Swift code you posted is a computed read-only property which is evaluated every time it is accessed.

这篇关于相当于懒惰的属性获取器的Swift的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！