[Objective-C] 08-self keyword

Note: This Objective-C topic is a prelude to iOS development. It also helps programmers with experience in object-oriented language development to quickly get started with Objective-C. If you have no programming experience or are not interested in Objective-C or iOS development, ignore this. Before learning this topic, we recommend that you first study the C language topic.

OC has a self keyword, which is similar to this in Java and represents the caller of the current method. However, there is a difference between self and this.

1. this in Java can only be used in dynamic methods, and cannot be used in static methods. 1. Use this keyword in dynamic methods.

1 public class Student {2     private int age;3     public void setAge(int age) {4         this.age = age;5     }6 }

This is used in row 4th. this indicates a Student object that calls the setAge method.

 

2. If this keyword is used in a static method, an error is reported.

 

Ii. self in OC can be used in both dynamic and static methods. 1. self is used in dynamic methods.

 1 @implementation Student 2  3 - (void)test2 { 4  5 } 6  7 - (void)test3 { 8     [self test2]; 9 }10 11 @end

* Two dynamic methods are defined in rows 3rd and 8th.

* The self keyword is used in row 8th. Here self represents a Student object that calls the test3 method.

* The function of the 8th line of code is to call the dynamic method test2 of the Student object.

 

2. self is in the static method

 1 @implementation Student 2  3 + (void)test2 { 4  5 } 6  7 + (void)test3 { 8     [Student test2]; 9     10     [self test2];11 }12 13 @end

* Two static methods are defined in rows 3rd and 7th, and the + number before the method is clearly displayed.

* Let's look at the second row. Here we use self. The self keyword is used in the static method test3.

* In the beginning, self indicates the caller of the current method. The current method is test3. Who is the caller of test3? It must be the Student class, because test3 is a static method. Therefore, self represents the Student class.

* Therefore, the functions of rows 8th and 10th are the same. The static method test2 is called.

 

3. self Summary

1> in a dynamic method, self represents an "object"

2> in static methods, self represents "class"

3> keep one sentence in mind. self indicates the caller of the current method.