NSMutableDictionary

NSMutableDictionary 用于处理值对集合。保存到键的对象必须实现了copyWithZone:方法。和NSMutableArray一样添加到容器时对象收到retain消息，把对象从容器中移除时收到release消息，任何想在移除对象还要对该对象进行操作必须先对该对象发出一条retain消息，在使用完成后需要release。

#import <Foundation/Foundation.h>



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

{



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



    //创建Dictionary,Capacity仅控制初始化大小

    NSMutableDictionary *fruits = [NSMutableDictionary dictionaryWithCapacity:2];

    [fruits setObject:@"Orange" forKey:@"OrangeKey"];

    [fruits setObject:@"Apple" forKey:@"AppleKey"];

    [fruits setObject:@"Blueberry" forKey:@"BlueberryKey"];

    NSLog(@"%@", fruits);

    

    //获取一个对象

    id oneObj = [fruits objectForKey:@"AppleKey"];

    NSLog(@"%@", oneObj);



    //如果找不到应的条目，返加nil

    id noObj = [fruits objectForKey:@"aaa"];

    NSLog(@"%@", noObj);

    

    [pool drain];

    return 0;

}