Objective-c中+和 - 方法之间的差异 [英] Difference between + and - methods in Objective-c

问题描述

用 - 声明的方法和用+

What is the difference between methods that are declared with - and methods that are declared with +

例如

- (void)methodname

+ (void)methodname

$ b b

推荐答案

以 - 为前缀的方法是实例方法。这意味着它们只能在类的实例上调用，例如：

Methods prefixed with - are instance methods. This means they can only be invoked on an instance of a class, eg:

[myStringInstance length];

以 + 为前缀的方法是类方法。这意味着它们可以在类上调用，而不需要一个实例，例如：

Methods prefixed with + are class methods. This means they can be called on Classes, without needing an instance, eg:

[NSString stringWithString:@"Hello World"];

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