@implementation 中声明的变量 [英] variables declared in @implementation

问题描述

我正在处理一本书中的代码清单，它有一对变量(特别是 NSString *)在@implementation 中而不是在@interface 中声明和初始化，但在任何方法体之外.我以前从未见过这个，我想知道这在范围等方面有什么不同.

I'm working through a code listing from a book and it has a pair of variables (specifically NSString *) declared and initialised in the @implementation rather than the @interface but outside of any method body. I've not seen this before and I'm wondering what the difference this makes in scope and so on.

我已经快速浏览了 The Objective C Programming Language，但我看不到任何描述其效果的内容.

I've had a quick look in The Objective C Programming Language but I can't see anything describing what effect this has.

谢谢

安迪

推荐答案

@implementation 内部声明的变量具有全局作用域.

Variables declared inside @implementation have global scope.

如果您将它们声明为静态"，则它们仅在同一源文件中的方法中可见.

If you declare them as "static", they are only visible from the methods in the same source file.

所以:

@implementation MyClass

NSString *myString; // global scope, and accessible by all code in your project

或

@implementation MyClass

static NSString *myString; // global scope, but only accessible by code 
                           // in this source file

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