objective-C 的OOP(下)-类，static方法、实例方法、overwrite

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] ----------------