ObjC方法类型编码字符串中的位数是多少? [英] What are the digits in an ObjC method type encoding string?

问题描述

我正在阅读 Apple的有关Objective-C运行时类型编码字符串的文章 某些方法的类型字符串中包含数字.

I'm reading Apple's article about Objective-C runtime type encoding strings and some methods have numbers in their type strings.

v12@0:4@8中的数字是什么意思?

What do the numbers in v12@0:4@8 mean?

推荐答案

这看起来像是setter方法的编码，如下所示:

This looks like an encoding of a setter method like this:

- (void) setSomething:(id) anObject

要分解它:

• v表示空返回类型
• 12表示参数帧的大小(12个字节)
• @0表示在参数帧的字节偏移量0处存在一个Objective-C对象类型(这是每个Objective-C方法中的隐式self对象)
• :4表示在字节偏移量4处有一个选择器(这是每个方法中的隐式_cmd，它是用于调用该方法的选择器).
• @8表示在字节偏移量8处还有另一种Objective-C对象类型.

• v means void return type
• 12 means the size of the argument frame (12 bytes)
• @0 means that there is an Objective-C object type at byte offset 0 of the argument frame (this is the implicit self object in each Objective-C method)
• :4 means that there is a selector at byte offset 4 (this is the implicit _cmd in every method, which is the selector that was used to invoke the method).
• @8 means that there is another Objective-C object type at byte offset 8.

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