为了更好的使得自己理解并掌握oc的语法，我在看完大部分oc的基础后，开始自己在notepad++上编辑一个测试的示例程序。

本以为很简单的几个类的程序，让我调试了好长时间，看来这种代码的编写方式真的是不错。让我对一些细小的地方更加的留意。

测试的程序主要包含了一个父类Animal、一个子类Dog、一个category-DogExt、一个protocol Print以及一个测试主程序文件main.

测试结果如下：有一点不符合我的预期结果，就是函数instancesRespondToSelector. Dog这个类明明有一个类方法printDogCount

可是结果却显示没有这个函数。后来我直接performSelector却可以执行了。同时我知道NSObject包含了一个返回类名的方法class

我将@selector(printDogCount)替换为@selector(class)却完美执行。真是奇怪！！！难道是bug不成。以后在关注吧。

测试结果：

Animal initialize

Dog initialize

There is 1 Dog(s)

2011-11-05 00:35:12.989 Hello[1339:707] Buddy

2011-11-05 00:35:12.990 Hello[1339:707]  Wow!

There is 4 feet of Dog!

There is 2 Dog(s)

2011-11-05 00:35:12.991 Hello[1339:707] Tom

2011-11-05 00:35:12.992 Hello[1339:707]  Wow!

dog is not a member Animal

dog is kind of Animal

dog respondsToSelector 'Wow' and performs it

2011-11-05 00:35:12.992 Hello[1339:707] Buddy

2011-11-05 00:35:12.993 Hello[1339:707]  Wow!

Dog not instancesRespondToSelector 'printDogCount'

There is 2 Dog(s)

dog can play ball by category ext

2011-11-05 00:35:12.993 Hello[1339:707] Buddy has 4 feet

dog conformsToProtocol Print

There is 3 Dog(s)

dog3 retain count=1

dog3 retain count=2

dog3 retain count=3

dog3 retain count=2

dog3 retain count=1

There is 2 Dog(s)

There is 1 Dog(s)

There is 0 Dog(s)

源码

Animal.h

/*

Animal Class

*/

#import <Foundation/Foundation.h>

#import "Print.h" //a protocol

@interface Animal : NSObject <Print>

{

NSString* _name;

}

-(Animal*) init;

-(void) Wow;

-(int) FeetNumber;

-(NSString*) Name;

-(void) setName : (NSString*) name ;

@end

Animal.m

#import "Animal.h"

#import <stdio.h>

@implementation Animal

+(void) initialize {

printf("Animal initialize\r\n");

}

-(Animal*) init

{

self = [super init];

_name = [[NSString alloc] initWithString : @"Animal"]; //自己分配内存

return self;

}

-(void) dealloc

{

[_name release];

}

-(void) Wow

{

printf("Animal Wow!\r\n");

}

-(int) FeetNumber

{

return -1;

}

-(NSString*) Name

{

return _name;

}

-(void) setName : (NSString*)new_name

{

[_name release]; //释放内存

_name = [new_name copy]; //拷贝后存放

}

//protocol

-(void) Print

{

NSString* str =  [[NSString alloc] initWithFormat:@"%@ has %i feet\r\n",_name,[self FeetNumber]];

NSLog(@"%@",str);

[str release];

}

@end

Dog.h

#import <Foundation/Foundation.h>

#import "Animal.h"

@interface Dog : Animal

{

@public //测试成员变量存取权限

int public_var;

@protected

int protected_var;

}

+(void) printDogCount; //类方法

@end

Dog.m

#import "Dog.h"

#import <stdio.h>

@implementation Dog

static int count = 0; //类似与类的静态变量

+(void) initialize {

printf("Dog initialize\r\n");

}

-(Dog*) init

{

self = [super init];

[self setName : @"Dog" ];

count ++ ;

[Dog printDogCount];//调用类方法

return self;

}

-(void) dealloc

{

count --;

[Dog printDogCount];

[super dealloc];

}

+(void) printDogCount

{

printf("There is %d Dog(s)\r\n",count);

}

-(void) Wow

{

NSLog(@"%@",[self Name]);

NSLog(@" Wow!\r\n");

}

-(int) FeetNumber //狗有四条腿

{

return 4;

}

@end

DogExt.h

#import "Dog.h"

@interface Dog (Ext)

-(void) PlayBall;

@end

DogExt.m

#import "DogExt.h"

@implementation Dog (Ext)

-(void) PlayBall

{

printf("dog can play ball by category ext\r\n");

}

@end

Print.h

@protocol Print

-(void) Print;

@end

main.m

#import <Foundation/Foundation.h>

#import <Foundation/NSAutoreleasePool.h>

#import <stdio.h>

#import "Dog.h"

#import "DogExt.h"

int main( int argc, const char *argv[] ) {

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

Dog *dog = [[Dog alloc] init ];

[dog setName : @"Buddy"];

[dog Wow];

int dog_feet = [dog FeetNumber]; //通过成员调用类方法

printf("There is %d feet of Dog!\r\n",dog_feet);

id dog2 = [[Dog alloc] init ];

[dog2 setName : @"Tom"]; //有method就反应,没有就不反应

[dog2 Wow];

dog->public_var = 2; //测试成员变量存取权限

//dog->protected_var = 5;

//dynamic types

if( [dog isMemberOfClass : [Animal class]] == YES )

{

printf("dog is a member Animal\r\n");

}

else

{

printf("dog is not a member Animal\r\n");

}

if( [dog isKindOfClass : [Animal class]] == YES )

{

printf("dog is kind of Animal\r\n");

}

else

{

printf("dog is not kind of Animal\r\n");

}

if([dog respondsToSelector : @selector(Wow) ] == YES)

{

printf("dog respondsToSelector 'Wow' and performs it\r\n");

[dog performSelector : @selector(Wow)];

}

else

{

printf("dog not respondsToSelector 'Wow' \r\n");

}

if([Dog instancesRespondToSelector : @selector(printDogCount) ] == YES)

{

printf("Dog instancesRespondToSelector 'printDogCount' \r\n");

}

else

{

printf("Dog not instancesRespondToSelector 'printDogCount' \r\n");

}

[Dog performSelector : @selector(printDogCount)];

//Categories

[dog PlayBall];

//protocol

id <Print> id_print = dog;

[id_print Print];

if( [dog conformsToProtocol : @protocol(Print)] == YES)

{

printf("dog conformsToProtocol Print\r\n");

}

//Memory

Dog *dog3 = [[Dog alloc] init];

printf("dog3 retain count=%d\r\n",(int)[dog3 retainCount]);

Dog *ref1 = [dog3 retain];

printf("dog3 retain count=%d\r\n",(int)[dog3 retainCount]);

Dog *ref2 = [dog3 retain];

printf("dog3 retain count=%d\r\n",(int)[dog3 retainCount]);

[dog3 release];

printf("dog3 retain count=%d\r\n",(int)[dog3 retainCount]);

[ref1 release];

printf("dog3 retain count=%d\r\n",(int)[dog3 retainCount]);

[ref2 release];

[dog release];

[dog2 release];

[pool release];

}

注：创建工程时选择Mac OS X下的Command Line ,Type:Foundation 不选择自动垃圾收集

工程文件下载 Hello.zip