为什么我可以在操场上设置私人场地 [英] Why I can set private field in playground

问题描述

我有一个简单的Vehicle类，其中有一个名为_odometer的 private 字段，然后，我有一个名为odometer的计算属性(它具有setter和getter)./p>

我认为_odometer不能设置，因为它是 private 字段，但是在操场上可以设置，为什么?这是我在操场上的代码:

如您所见，我创建了一个名为volvo的Vehicle实例.默认情况下，_odometer是500，但是我可以直接在volvo上将_odometer设置为 0 ，当打印出里程表"时，它是 0 . 为什么，我可以设置私有字段吗?

解决方案

Swift private在语义上与其他OO语言略有不同，它是源文件专用的.

在 Swift访问控制中:

私有访问将实体的使用限制为自己定义 源文件.使用私有访问权限隐藏实施细节 特定功能.

I have a simple Vehicle class which has a private field named _odometer, then, I have a computed-property named odometer(it has setter & getter).

I think _odometer should not be able to set since it is a private field, but in playground, it can be set, why? Here is my code in play ground:

As you can see, I created an instance of Vehicle named volvo. By default _odometer is 500, but I can directly set _odometer to 0 on volvo, when print out the 'odometer', it is 0. WHY I can set private field?

解决方案

Swift private is slightly semantically different than in other OO languages, it is private to the source file.

In Swift Access Control:

Private access restricts the use of an entity to its own defining source file. Use private access to hide the implementation details of a specific piece of functionality.

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