OC Language Construction method

First, the construction method

(i) Call to construct method

Complete creation of an available object: Person*p=[person new];

the inner part of the New method calls two methods to accomplish 2 things,1) Use the Alloc method to allocate storage space (return allocated objects);2) use init method to initialize the object.

The new method can be opened as follows:

1. Call the class method +alloc Allocate storage space and return uninitialized objects

Person *p1=[person alloc];

2. Call object method -init to initialize, return the object itself

Person *P2=[P1 Init];

3. The above two processes are integrated into one sentence:

Person *p=[[person alloc] init];

Description: The Init method is the constructor method, the method used to initialize the object, note that this is an object method, and a minus sign begins. After the default initialization is complete, all member variables have a value of 0.

(ii) Code Examples of construction methods

Need 1, if I need to let each object create the initial value is ten, instead of 1, what should I do?

Demand 2, let students inherit human, ask students to initialize the object, the age is ten, the number is 1, how to do?

(iii) Construction method use note

(1) A subclass has member variables that include its own member variables and member variables inherited from the parent class, and the member variables that inherit from the parent class should be initialized first when overriding the constructor method.

(2) Principle: Initialize the parent class first, and then initialize the subclass.

(3) The purpose of overriding the construction method: In order for the object method to be created, the member variable will have some fixed value.

(4) Note:#1 First Call the constructor method of the parent class [Super Init]; #2 The initialization of the member variables inside the subclass.

Ii. Custom Construction methods

(i) Specification of custom construction methods

(1) must be an object method, starting with a minus sign

(2) The return value is typically an ID type

(3) method names usually start with Initwith

(ii) Code implementation of custom construction methods

Declaration of the Person class, which declares a custom construction method of two receive parameters

Implementation of the Person class

Student inherits from the person class and declares a constructor method that receives three parameters

Implementation of the Student class

Test the main program

(iii) Use of custom construction methods note

(1) Do your own thing

(2) The method of the parent class is given to the parent class's method to handle, and the subclass's method handles the subclass's own unique properties

OC Language Construction method