Objective-C-类（static）方法、实例方法、overwrite（覆写）、属性（property）复习

先来定义一个Human父类

定义部分：

//
//  Human.h
//  OOP
//
//  Created by jimmy.yang on 11-2-9.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import <Foundation/Foundation.h>


@interface  Human : NSObject  {
    BOOL  sex;
}

+( void ) toString;

-( void ) showSex;

@end

注：+(void)前的加号，就表示这一个是类方法(static 方法)，而-(void)表示这是一个实例方法

实现部分：

注意：下面的 -(id) init 即为构造函数。对应的，还有一个-(void)dealloc方法用来释放资源（类似于析构函数或c#中的dispose()方法）-注：dealloc方法以后在内存管理中详细学习，这里先不管它。

//
//  Human.m
//  OOP
//
//  Created by jimmy.yang on 11-2-9.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "Human.h"


@implementation  Human

//构造函数
-( id ) init
{
    NSLog (@ "init() in Human is called" );
    sex = TRUE;
    return ( self );
}

//static类方法
+ ( void )toString
{
    NSLog (@ "this is a class method of Human" );
}


//实例方法
- ( void )showSex
{
    NSLog (@ "my sex is %@" ,sex?@ "MALE" :@ "FEMALE" );
}


@end

再来定义一个Woman子类

定义部分：

//
//  Woman.h
//  OOP
//
//  Created by jimmy.yang on 11-2-9.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "Human.h"


@interface  Woman : Human {
    BOOL  married;
}

-( void ) canCook:( NSString *) foodName;

-( void ) setMarried:( BOOL )m;

-( BOOL ) Married;

@end

实现部分：

注意下面的：setMarried 与 Married 就是obj-C中属性的标准写法(当然以后还能看到其它简化的写法)

//
//  Woman.m
//  OOP
//
//  Created by jimmy.yang on 11-2-9.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "Woman.h"


@implementation  Woman

//Woman类的构造函数
-( id ) init{
    NSLog (@ "init() in Woman is called!" );
    if  ( self ==[ super  init]){
        sex = FALSE;
        married = FALSE;
    }
    return  ( self );
}

//overwrite父类中的toString()
+( void )toString
{
    NSLog (@ "This is Woman's ToString()" );
}

//Woman能做饭
-( void )canCook:( NSString *) foodName
{
    NSLog (@ "I can cook %@" ,foodName);
}

//属性的setter
-( void ) setMarried:( BOOL )m
{
    married = m;
}

//属性的getter
-( BOOL ) Married
{
    return  married;
}

@end

main方法中的调用：

#import <Foundation/Foundation.h>
#import "Human.h"
#import "Woman.h"

int  main ( int  argc, const  char  * argv[]) {
    NSAutoreleasePool  * pool = [[ NSAutoreleasePool  alloc] init];

    // insert code here...
    NSLog (@ "Hello, World!" );

    //调用类的“静态”方法
    [Human toString];

    NSLog (@ "----------------" );

    //创造一个Human的实例
    Human *man = [Human new ];

    //调用man的showSex方法
    [man showSex];

    NSLog (@ "----------------" );

    //定义一个Woman子类的实例
    Woman *wife = [Woman new ];
    [wife canCook:@ "Rice" ];

    //调用继承自父类的方法
    [wife showSex];

    //设置属性
    [wife setMarried:TRUE];

    //读取属性值
    NSLog (@ "wife's married = %@" ,wife.Married== NO ?@ "FALSE" :@ "TRUE" );

    NSLog (@ "----------------" );

    //调用overwrite后的toString方法
    [Woman toString];


    //Factory模式中常用的手法，在这里依然适用(只不过编译时会有警告 'Human' may not respond to '-canCook:')
    Human *wife2 = [Woman new ];
    [wife2 canCook:@ "soap" ];



    NSLog (@ "----------------" );

    [pool drain];
    return  0;
}

 运行结果：

2011-02-09 17:01:02.016 OOP[1725:a0f] Hello, World!
2011-02-09 17:01:02.053 OOP[1725:a0f] this is a class method of Human
2011-02-09 17:01:02.062 OOP[1725:a0f] ----------------
2011-02-09 17:01:02.075 OOP[1725:a0f] init() in Human is called
2011-02-09 17:01:02.091 OOP[1725:a0f] my sex is MALE
2011-02-09 17:01:02.094 OOP[1725:a0f] ----------------
2011-02-09 17:01:02.099 OOP[1725:a0f] init() in Woman is called!
2011-02-09 17:01:02.104 OOP[1725:a0f] init() in Human is called
2011-02-09 17:01:02.105 OOP[1725:a0f] I can cook Rice
2011-02-09 17:01:02.108 OOP[1725:a0f] my sex is FEMALE
2011-02-09 17:01:02.109 OOP[1725:a0f] wife's married = TRUE
2011-02-09 17:01:02.111 OOP[1725:a0f] ----------------
2011-02-09 17:01:02.116 OOP[1725:a0f] This is Woman's ToString()
2011-02-09 17:01:02.120 OOP[1725:a0f] init() in Woman is called!
2011-02-09 17:01:02.121 OOP[1725:a0f] init() in Human is called
2011-02-09 17:01:02.123 OOP[1725:a0f] I can cook soap
2011-02-09 17:01:02.125 OOP[1725:a0f] ----------------

作者： 菩提树下的杨过
出处： http://yjmyzz.cnblogs.com 
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原文：http://www.cnblogs.com/yjmyzz/archive/2011/02/09/1950305.html