Objective－C的字典类NSDictionary

1.初始化

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1. //初始化一组数组，存入字典中作为关键字  
2. NSNumber *num = [NSNumber numberWithInt:100];  
3. NSDictionary *dic1 = [NSDictionary dictionaryWithObject:num forKey:@"key1"];  
4.   
5. //初始化多组数据  
6. NSDictionary *dic2 = [NSDictionary dictionaryWithObjectsAndKeys:@"hello",@"key2",@"world",@"key3",@"csdn",@"key4", nil nil];  
7.   
8. //用一个字典初始化另外一个字典  
9. NSDictionary *dic3 = [NSDictionary dictionaryWithDictionary:dic2];  
10.   
11. //打印输出  
12. NSLog(@"dic1 :  %@,dic2  :  %@,  dic3   :   %@",dic1,dic2,dic3);  

输出：dic1 :{

    key1 = 100;

},dic2  :  {

    key2 = hello;

    key3 = world;

    key4 = csdn;

},  dic3   :   {

    key2 = hello;

    key3 = world;

    key4 = csdn;

}

2.获取字典的值

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1. //获取长度  
2. int length = [dic2 count];  
3. NSLog(@"dic2 length = %d",length);  
4.   
5. //根据key获取key所对应的value  
6. NSLog(@"key3 value = %@",[dic2 objectForKey:@"key3"]);  
7.   
8. //可以获取所有的keys  
9. NSArray *allkeys =  [dic3 allKeys];  
10. NSLog(@"NSarray allkey = %@",allkeys);  
11.   
12. //可以获取所有的values  
13. NSArray *allvalues =  [dic3 allValues];  
14. NSLog(@"NSarray allvalues = %@",allvalues);  

输出：dic2  length ＝ 3

     key3 value = world

     NSarray allkey = (

          key4,

          key3,

          key2

     )

     NSarray allvalues = (

          csdn,

          world,

          hello

     )

3.可变字典

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1. //----- 初始化  
2. NSMutableDictionary *dic4 = [NSMutableDictionary dictionaryWithObjectsAndKeys:@"one",@"key4",@"two",@"key5", nil nil];  
3.   
4. //定义成空字典  
5. NSMutableDictionary *dic5 = [NSMutableDictionary dictionary];  
6.           
7. //将字典dic2整体添加到dic4钟  
8. [dic4 addEntriesFromDictionary:dic2];  
9.   
10. //添加一个元素  
11. [dic4 setValue:@"three" forKey:@"key6"];  
12.   
13. //根据key获取value  
14. NSLog(@"key6 =  %@",[dic4 objectForKey:@"key6"]);  

4.字典的遍历

（1）一般遍历

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1. NSArray *keys4 = [dic4 allKeys];  
2.           
3. for(int i=0;i<[dic4 count];i++)  
4. {  
5.           
6.     NSLog(@"dic4 key = %@,value=%@",[keys4 objectAtIndex:i],[dic4 objectForKey:[keys4 objectAtIndex:i]]);  
7. }  

输出：dic4 key = key3,value=world

     dic4 key = key6,value=three

     dic4 key = key4,value=csdn

     dic4 key = key2,value=hello

     dic4 key = key5,value=two

（2）高效的for遍历

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1. for (NSString *key in dic4)  
2. {  
3.      NSLog(@"dic4 key = %@ ,value = %@",key,[dic4 objectForKey:key]);  
4. }  

输出：dic4 key = key3,value=world

     dic4 key = key6,value=three

     dic4 key = key4,value=csdn

     dic4 key = key2,value=hello

     dic4 key = key5,value=two

（3）枚举遍历

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1. NSEnumerator *enum1 = [dic4 keyEnumerator];  
2. //获取key,如果不为空，则进行偏移  
3. id key = [enum1 nextObject];  
4. while (key)   
5. {            
6.     NSLog(@"key = %@ ,value = %@ ",key,[dic4 objectForKey:key]);  
7.               
8.     key = [enum1 nextObject];  
9. }  

输出：dic4 key = key3,value=world

     dic4 key = key6,value=three

     dic4 key = key4,value=csdn

     dic4 key = key2,value=hello

     dic4 key = key5,value=two