常用方法
-(void)setObject:(id)anObject forKey:(id <NSCopying>)aKey;
添加一个键值对（会把aKey之前对应的值给替换掉）
-(void)removeObjectForKey:(id)aKey;
通过aKey删除对应的value
-(void)removeAllObjects;
删除所有的键值对


[dict1 setValue:@"lisi" forKey:@"ls"];

常用方法
-(void)setObject:(id)anObject forKey:(id <NSCopying>)aKey;
添加一个键值对（会把aKey之前对应的值给替换掉）
-(void)removeObjectForKey:(id)aKey;
通过aKey删除对应的value
-(void)removeAllObjects;
删除所有的键值对


[dict1 setValue:@"lisi" forKey:@"ls"];