OC for iOS Development (eight)--supplement to the Little Knowledge supplement Init method

Small Knowledge Supplement

First, ID

1. Introduction

A universal pointer that can point to any OC object, equivalent to NSObject *

Definition of ID Type

struct Objc_object {        *ID;

2. Use

Note: Do not add * after ID

ID p = [person new];

3. Limitations

Call a non-existent method, the compiler will immediately error

Ii. extraction of files of. h and. m

1) Each class is distributed in different files

2) The declaration of the class is placed in the. h file, the implementation of the class is placed in the. m file

3) If you want to use a class, include the. h declaration file for a class

iii. addition of the Init method (emphasis)

1. Principle of object creation

New Split two-part song

U Allocate Memory (+ALLOC)

U initialization (-init)

Person *P1 =*p1 =*p = [[Person alloc] init];

2. Overriding the Init method

L WANT the member variable to have some default values right after the object is created

L Rewrite process of init method

-(ID) init{
1. Be sure to call Super's Init method: Initialize some member variables and other properties declared in the parent class
Self  = [super init];   Current Object Self
2. If the initialization succeeds, it is necessary to proceed with the     next initialization if (self = [super init])    {//Initialize        success   ;    }     return Self ;//3. Returns a value that has already been initialized}

3. Custom Construction methods

Some specifications of the L-structure method

• -(ID) initwithage: (int) Age {    if "self = [super init]")        {= age ;    }     return Self ;}

  Pass multiple parameters for initialization

  -(ID) initwithage: (int) Age Andno: (int) No;

  The return value is the ID type

• Method names start with Init

OC for iOS Development (eight)--supplement to the Little Knowledge supplement Init method