如何快速访问视图子层 [英] How to access view sublayers in swift

问题描述

我想通过以下方式在swift 4.1中访问视图子层：

I would like to access view sublayers in swift 4.1 by writting :

for layer : CALayer in myView.layer.sublayers {
         // Code
}

，但收到错误：

类型'[CALayer]？'不符合协议'Sequence'

Type '[CALayer]?' does not conform to protocol 'Sequence'

是否意味着for循环无法访问 CALayer ？

Does that mean that CALayer is unreachable by for loop ?

推荐答案

子层属性是一个可选数组（默认情况下 nil ）。
您必须先将其解开，例如并具有可选的绑定：

The sublayers property is an optional array (and by default nil). You have to unwrap it first, e.g. with optional binding:

if let sublayers = myView.layer.sublayers {
    for layer in sublayers {
        // ...
    }
}

或者具有可选的链接和 forEach ：

Alternatively with optional chaining and forEach:

myView.layer.sublayers?.forEach { layer in
    // ...
}

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