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

2024-07-17 20:51:05   218人阅读

先来定义一个Human父类

定义部分：

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//
//  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。

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//
//  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：

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//
//  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)

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//
//  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：

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#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] ----------------


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