差异类和实例方法 [英] Difference Class and Instance Methods

问题描述

类方法和实例方法之间的区别是什么?为什么我们需要单独使用它们? 有人可以解释一下吗?

Whats the difference between class methods and Instance methods. Why do we need them separately? Can somebody please explain?

类和实例方法

•实例响应实例方法

 - (id)init;
 - (float)height;
 - (void)walk;

•类响应类方法

 + (id)alloc;
 + (id)person;
 + (Person *)sharedPerson;

Taimur

推荐答案

实例方法仅在类的实例上可用，而类方法不需要实例，但在类上可用.

An instance method is only available on an instance of the class, while a class method does not need an instance but is available on the class.

类方法用+表示，而实例方法用其返回类型前的-表示.

Class Methods are denoted by a + while instance methods are denoted by a - before their return type.

让我们以NSObject为例. NSObject具有一个名为+ (id)alloc的类方法. alloc方法用于分配类的实例.显然，alloc必须是一个类方法，因为如果它是一个实例方法，那么您将从何处获得根"实例?

Let's take NSObject for example. NSObject has a class method named + (id)alloc. The alloc method is used to allocate an instance of the class. Obviously alloc must be a class method because if it was an instance method, where would you get the "root" instance from?

另一方面，- (id)init是一种实例方法，因为它可以初始化实例的状态.

On the other hand - (id)init is an instance method because it initializes the state of an instance.

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