NSDictionary类使用

NSDictionary类使用
http://www.cnblogs.com/luyinghuai/archive/2011/02/15/1955238.html

字典就是关键字及其定义（描述）的集合。Cocoa中的实现字典的集合NSDictionary在给定的关键字（通常是一个NSString）下存储一个数值（可以是任何类型的对象）。然后你就可以用这个关键字来查找相应的数值。
不同于数组，字典（也被称为散列表或关联数组）使用的是键查询的优化存储方式。它可以立即找出要查询的数据，而不需要遍历整个数组进行查找。
可使用dictionaryWithObjectsAndKeys来创建字典
查询字典的值：objectForKey
NSMutableDictionary的dictionary方法可以创建一个可变字典，也可以使用dictionaryWithCapaticy：。
使用 setObject:forkey: 方法添加字典元素，如果关键字已存在，则用新植替换旧值。
类似的，NSMutableDictionary类允许随意添加或删除字典元素。
添加元素：setObject:forkey:
删除元素：removeObjectForKey:
Example:

	

		 1 //  2  // MyClass.h  3  // FoundationKit4  4  //  5  // Created by Elf Sundae on 10/22/10.  6 // Copyright 2010 Control-Strength. All rights reserved.  7 //  8   9 #import <Cocoa/Cocoa.h> 10  11  12 @interface MyClass : NSObject 13 { 14  NSString *firstName; 15  NSString *lastName; 16 } 17  18  19 - (void) setFirstName:(NSString *)m_firstName; 20 - (NSString *) firstName; 21  22 - (void) setLastName: (NSString *) m_lastName; 23 - (NSString *) lastName; 24  25  26 @end
	

 

	

		 1 //  2 // MyClass.m  3 // FoundationKit4  4 //  5 // Created by Elf Sundae on 10/22/10.  6 // Copyright 2010 Control-Strength. All rights reserved.  7 //  8   9 #import "MyClass.h" 10  11  12 @implementation MyClass 13  14 - (void) setFirstName:(NSString *)m_firstName{ 15  16  firstName = m_firstName; 17 } 18 - (NSString *) firstName{ 19 return firstName; 20 } 21  22 - (void) setLastName: (NSString *) m_lastName{ 23  lastName = m_lastName; 24 } 25 - (NSString *) lastName{ 26 return lastName; 27 } 28  29  30 - (NSString *) description 31 { 32 if (firstName == nil || lastName == nil) { 33 return @"No Name found."; 34  } else { 35 return [NSString stringWithFormat:@"%@ %@", 36  firstName,lastName]; 37  } 38  39 } 40  41 @end
	

 

	

		 1 /*  2  * 示例字典（NSDictionary,NSMutableDictionary）操作  3  *  4  * Elf Sundae  10/22/2010  5 */  6   7 #import <Foundation/Foundation.h>  8 #import "MyClass.h"  9  10 int main (int argc, const char * argv[]) { 11  NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; 12  13 // 创建字典：dictionaryWithObjectsAndKeys: 14  MyClass *my1 = [MyClass new]; 15  MyClass *my2 = [MyClass new]; 16  MyClass *my3 = [MyClass new]; 17  MyClass *my4 = [MyClass new]; 18  19  NSDictionary *myClassDict; 20  myClassDict = [NSDictionary dictionaryWithObjectsAndKeys: 21  my1, @"my1", 22  my2, @"my2", 23  my3, @"my3", 24  my4, @"my4", nil]; 25 // 获取值 objectForKey 26  MyClass *sub = [myClassDict objectForKey: @"my3"]; 27 if (sub == nil) { 28  exit(1); 29  } 30  [sub setFirstName:@"Elf"]; 31  [sub setLastName:@"Sundae"]; 32  33  NSLog(@"修改数据： %@",sub); 34  35 // 遍历字典 36  NSLog(@"***遍历字典myClassDict如下："); 37 for (id key in myClassDict) 38  { 39  NSLog(@"key: %@ ,value: %@",key,[myClassDict objectForKey:key]); 40  } 41  NSLog(@"***遍历字典myClassDict结束。"); 42  43 // MARK: ***  添加新元素  *** 44 // NSDictionary无法添加或删除元素，可以使用NSMutableDictionary. 45  NSMutableDictionary *myNewDict = [NSMutableDictionary dictionary]; 46 // 将原有字典添加到新字典的一对元素 47 //[myNewDict setObject:myClassDic forKey:@"旧的不可变字典myClassDic"]; 48  49 // 遍历添加已有数据(原字典) 50 for (id key in myClassDict) 51  { 52  [myNewDict setObject: [myClassDict objectForKey:key] 53  forKey:key]; 54  } 55  56  NSString *newkey = @"newKey"; 57  NSString *newValue = @"This is a new Value."; 58  [myNewDict setObject:newValue forKey:newkey]; 59  60 // 遍历myNewDict 61  NSLog(@"***遍历字典myNewDict如下："); 62 for (id key in myNewDict) 63  { 64  NSLog(@"key: %@ ,value: %@",key,[myNewDict objectForKey:key]); 65  } 66  NSLog(@"***遍历字典myNewDict结束。"); 67  68 // 删除元素 69  [myNewDict removeObjectForKey: @"newKey"]; 70  71 // 遍历myNewDict 72  NSLog(@"***遍历字典myNewDict如下："); 73 for (id key in myNewDict) 74  { 75  NSLog(@"key: %@ ,value: %@",key,[myNewDict objectForKey:key]); 76  } 77  NSLog(@"***遍历字典myNewDict结束。"); 78  79  [pool drain]; 80 return 0; 81 }
	

 

 

// 输出结果（省略日期 时间等信息）
修改数据： Elf Sundae
***遍历字典myClassDict如下：
key: my3 ,value: Elf Sundae
key: my4 ,value: No Name found.
key: my1 ,value: No Name found.
key: my2 ,value: No Name found.
***遍历字典myClassDict结束。
***遍历字典myNewDict如下：
key: newKey ,value: This is a new Value.
key: my3 ,value: Elf Sundae
key: my4 ,value: No Name found.
key: my1 ,value: No Name found.
key: my2 ,value: No Name found.
***遍历字典myNewDict结束。
***遍历字典myNewDict如下：
key: my3 ,value: Elf Sundae
key: my4 ,value: No Name found.
key: my1 ,value: No Name found.
key: my2 ,value: No Name found.
***遍历字典myNewDict结束。