OC学习 第八章 NSDictionary和NSMutabledictionary

OC学习 第七章 NSDictionary和NSMutabledictionary

一、NSDictionary

1.创建

NSDictionary*dic = [NSDictionarydictionary];//创建一个空的字典

NSDictionary*dic1 = [NSDictionarydictionaryWithObject:@"object"forKey:@"key"];//创建包含一个键值对的字典

NSDictionary*dic2 = [NSDictionarydictionaryWithObjectsAndKeys:

@"123",@"abc",@"234",@"aaa",nil];//创建包含多个键值对的字典

NSLog(@"%@",dic2);

NSDictionary*dic3 =@{

@“a”(key):@“12”(value),

@"b":@“23"
};

NSLog(@"%@",dic3);

2.字典的常用方法

int count = dic3.count;//字典键值对的个数

NSLog(@"%zi",dic3.count);

NSString *s = [dic3
objectForKey:@"a"];//获取某关键字（key）对应的值

NSString *s1 = dic3[@"b"];

NSLog(@"%@",s1);
3.字典的遍历
一、 先取出字典中所有的key，放入一个数组，然后对该数组进行遍历，便利过程中，根据key取值

NSArray*keyArr =
[dic3allKeys];

for(NSString*keyinkeyArr)
{

NSLog(@"%@
= %@",key,dic3[key]);

}
二、取出字典中所有的值，同上

NSArray*valueArr
= [dic3allValues];
三、
先获取字典中key的枚举器，然后遍历该枚举器，获取key对应的值

NSEnumerator *e = [dic3keyEnumerator];

id obj;

while (obj = [e nextObject]) {

NSLog(@"%@ = %@",obj,dic3[obj]);

}
二、NSMutabledictionary
1.创建 NSMutableDictionary *dic = [NSMutableDictionary dictionary];//初始化一个空的可变字典

NSMutableDictionary *dic1 = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"a",@"1", nil];

//增

[dic setObject:@"12" forKey:@"b"];

[dic setValue:@"234" forKey:@"c"];

NSLog(@"%@",dic);

//删

[dic removeAllObjects];//移除所有的键值对

[dic removeObjectForKey:@"c"];//移除某个key对应的键值对