OC - 字典常用方法

字典是无序的  数组是有序的 

字典分为：可变字典和不可变字典 

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--------不可变字典对象 NSDictionary * dict = [[NSDictionary alloc]initWithObjectsAndKeys:@ "one" ,@ "1" ,@ "two" ,@ "2" ,@ "three" ,@ "3" ,@ "four" ,@ "4" , nil];      //value = key      //初始化必须一一对应  字典的内容是键值对   key->value  内容可以是任意的对象指针      //key   一般是NSString *   value   可以是任意对象      //不能出现重复的key    key是唯一的   NSDictionary * dict1 = [NSDictionary dictionaryWithDictionary:dict];   NSArray * values = [NSArray arrayWithObjects:@ "one" ,@ "two" ,@ "three" , nil]; NSArray * keys = [NSArray arrayWithObjects:@ "1" ,@ "2" ,@ "3" , nil]; //key-value要一一对应 NSDictionary * dict2 = [[NSDictionary alloc]initWithObjects:values forKeys:keys];   [dict count] //键值对的个数    键值对必须成对出现 [dict objectForKey:@ "5" ] //根据key找到对应的value   //创建一个key的枚举器   把字典中key元素地址传给枚举器 NSEnumerator * enumer1 = [dict keyEnumerator]; id obj; while (obj = [enumer1 nextObject]) {      NSLog(@ "%@" ,[dict objectForKey:obj]); }       //创建值的枚举器(一般不使用，没有意义) NSEnumerator * enumer2 = [dict objectEnumerator]; while (obj = [enumer2 nextObject]) {       NSLog(@ "%@" ,obj); } //快速枚举 枚举的是key(不能改数据,只能读) for (id key in dict){       NSLog(@ "%@" ,key); }   NSArray * array = [urlItemDict allValues]; //获取所有value NSArray * array = [urlItemDict allKeys]; //获取所有key------可变字典对象

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------可变字典对象   NSMutableDictionary * dict = [[NSMutableDictionary alloc]initWithObjectsAndKeys:@ "one" ,@ "1" ,@ "two" ,@ "2" ,@ "three" ,@ "3" ,@ "four" ,@ "4" , nil];           [dict setObject:@ "seven" forKey:@ "7" ]; //增加键值对   key已经存在 则修改value        不存在则添加 [dict setObject:@ "nine" forKey:@ "1" ]; //修改value [dict removeObjectForKey:@ "1" ]; //删除键值对