类方法和实例方法的区别
类方法和实例方法有什么区别。为什么我们需要单独使用它们？ 有人可以解释一下吗？
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
Whats the difference between class methods and Instance methods. Why do we need them separately?
Can somebody please explain?
Class and Instance Methods
• Instances respond to instance methods
- (id)init;
- (float)height;
- (void)walk;
• Classes respond to class methods
+ (id)alloc;
+ (id)person;
+ (Person *)sharedPerson;
Taimur
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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。
类方法由
+表示，而实例方法在其返回类型之前由-表示。我们以 NSObject 为例。
NSObject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，那么您将从哪里获得“根”实例？另一方面，
- (id)init是一个实例方法，因为它初始化实例的状态。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.
Class Methods are denoted by a
+while instance methods are denoted by a-before their return type.Let's take
NSObjectfor example.NSObjecthas 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?On the other hand
- (id)initis an instance method because it initializes the state of an instance.一个例子：
Human->类你->实例人类可以消灭，你不能。你可以喝可乐，人类不能。Instance方法仅适用于个体，而
Class方法适用于具有相同可识别特征的整个群体。这是一个与许多、个人与整个社会之间的区别。
[SomeClass alloc]表示该类的新实例诞生就像你出生一样，
init适用于一个Instance，就像你的父母给你起名字，养活你，送你上学，这样你就有了生活的技能这个社会。An example:
Human->ClassYou->InstanceHumancouldextinguish,youcannot.Youcoulddrink a Coke,Humancannot.Instancemethod is only applied to individuals,While
Classmethod is applied to the whole group with the same identifiable features.It's the difference between one and many, individual and the whole society.
[SomeClass alloc]means a new instance of the class is bornjust like You are given birth,
initapplies to anInstance, like your parents give you a name, feed you and send you to school, so you have skills to live in this society.