Dark Horse Programmer--oc Language class method and self keyword

A) Comparison of object methods and class methods

Object methods

1> minus-Start

2> can only be called by an object

A member variable (instance variable) that can access the current object in the 3> object method

Class method

1> Plus + start

2> can only be called by Class (name)

Member variables (instance variables) cannot be accessed in the 3> class method

The benefits and applications of class methods

1> is not dependent on the object, the execution efficiency is high

2> can use class method, try to use class method

3> occasions: You can change to a class method when you do not need to use a member variable inside a method

II) Self

Use of self:

1> who calls the current method, self represents who

* Self appears in the object method, and self represents the object

* Self appears in the class method, and self represents the class

2> accessing member variables inside the current object using the "self-> member variable name" in the object method

[Self method name] can call object method \ class method

Common errors:

• Low-level error: calling function with self
• The object method is called with self in the class method, and the class method is called with self in the object method
• Self dead Loop

Example: Designing a Calculator class for summing and averaging

Declaration of the class:

Implementation of the class:

Dark Horse Programmer--oc Language class method and self keyword