一:字典的基本概念

    Foundation中的字典(NSDictionary，NSMutableDictionary)是由鍵-值對(duì)組成的數(shù)據(jù)集合.正如,我們?cè)谧值淅锊檎覇卧~的定義一樣.

通過(guò)key(鍵)，查找的對(duì)應(yīng)的value(值),key通常是字符串對(duì)象,也可以是其他任意類型對(duì)象.在一個(gè)字典對(duì)象中，key的值必須是唯一的.

此外,字典對(duì)象的鍵和值不可以為空(nil),如果需要在字典中加入一個(gè)空值，可以加入NSNull對(duì)象

二:不可變字典-NSDictionary

   1:初始化(以一個(gè)元素和多個(gè)元素進(jìn)行初始化):

     //以一個(gè)鍵值對(duì)象 進(jìn)行初始化

        NSDictionary *dict1=[NSDictionary dictionaryWithObject:numObj1 forKey:@"key1"];         NSLog(@"%@",dict1);         //以多個(gè)元素進(jìn)行初始化         NSDictionary *dict2=[NSDictionary dictionaryWithObjectsAndKeys:numObj1, @"key1",numObj2,@"key2", nil];         NSLog(@"%@",dict2);
 2:獲取字典的數(shù)量
	
 		//獲取字典的數(shù)量 	
  	
 		        NSInteger count=[dict2 count]; 	
  	
 		        NSLog(@"%ld",count); 	
  	
 		3:根據(jù)key獲取相應(yīng)的value對(duì)象 	
  	
 		//根據(jù)key獲取相應(yīng)的value對(duì)象 
        NSString *value=[dict2 objectForKey:@"key1"];         NSLog(@"%@",value);
4:把字典的key轉(zhuǎn)換成枚舉對(duì)象用于遍歷
  NSEnumerator *enumerator=[dict2 keyEnumerator];
5:獲取所有的key集合
 //獲取所有的key集合
        NSArray *keys= [dict2 allKeys];         NSLog(@"%@",keys);
6：獲取所有的value集合
 //獲取所有的value集合
        NSArray *values=[dict2 allValues];         NSLog(@"%@",values);
三:可變字典NSMutableDictionary繼承自NSDictionary
 1:初始化字典
  //初始化字典         NSMutableDictionary *mutableDic=[[NSMutableDictionary alloc]initWithObjectsAndKeys:@"v1",@"k1",@"v2",@"k2",@"v3",@"k3",@"v4",@"k4",@"v5",@"k5", nil];
2:向字典中添加指定的字典
 //向一個(gè)字典中添加一個(gè)字典
        NSDictionary *dict4=[NSDictionary dictionaryWithObject:@"v6" forKey:@"k6"];         [mutableDic addEntriesFromDictionary:dict4];         NSLog(@"%@",mutableDic);
3:向字典中添加value和key

//向字典中添加value和key         [mutableDic setValue:@"object" forKey:@"key"]; 
4：創(chuàng)建空的字典,然后設(shè)置新的一個(gè)字典
 //創(chuàng)建空的字典,然后設(shè)置新的一個(gè)字典,把會(huì)之前的字典全部覆蓋掉         NSMutableDictionary *mutableDict2=[NSMutableDictionary dictionary];         [mutableDict2 setDictionary:mutableDic];         NSLog(@"%@",mutableDict2);
5:刪除指定key的value值
 
 //移除指定key的value值         [mutableDict2 removeObjectForKey:@"k4"];         NSLog(@"%@",mutableDict2);
6：刪除移除key集合的value值
//刪除一組key的value值         NSArray *arrayKeys=[NSArray arrayWithObjects:@"k1",@"k2",@"k3", nil];         [mutableDict2 removeObjectsForKeys:arrayKeys];         NSLog(@"%@",mutableDict2); 
7:刪除字典中所有的value
  //刪除字典中所有的數(shù)據(jù)
        [mutableDict2 removeAllObjects];         NSLog(@"%@",mutableDict2); 
四:枚舉遍歷
 1:一般遍歷
 //一般遍歷
        NSArray *allKeys=[mutableDic allKeys];         for (NSInteger i=0; i<[allKeys count]; i++) {             NSString *obj=[mutableDic objectForKey:[allKeys objectAtIndex:i]];                          NSLog(@"%@",obj);         } 
 2：快速枚舉
 //快速遍歷
     for (id key in mutableDic) {         NSString *object=[mutableDic objectForKey:key];         NSLog(@"%@",object);     }
3：迭代器枚舉
 
  //枚舉器       NSEnumerator *enumerator1= [mutableDic keyEnumerator];         id key=[enumerator1 nextObject];         while (key) {             id object=[mutableDic objectForKey:key];             NSLog(@"%@",object);             key=[enumerator1 nextObject];         }