本文主要是介绍字典:NSDictionary-回忆,希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!
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:
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
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
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。
这篇关于字典:NSDictionary-回忆的文章就介绍到这儿,希望我们推荐的文章对编程师们有所帮助!