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[OC Foundation框架 - 10] NSDictionary
通过唯一的key找到相应的value，类似于Map
NSDictionary是不可变的
1.创建
1 void dicCreate() 2 { 3 //Immutable 4 // NSDictionary *dic = [NSDictionary dictionary]; 5 6 NSDictionary *dic = [NSDictionary dictionaryWithObject:@"Simon" forKey:@"name"]; 7 8 dic = [NSDictionary dictionaryWithObjectsAndKeys:@"v1", @"k1", @"v2", @"k2", nil]; 9 10 NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil];11 NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil];12 dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys];13 14 NSLog(@"%@", dic);15 16 }
集中批量创建字典
1 NSDictionary *d11_1 = @{@"姓名":@"张三", @"年龄":@"21", @"性别":@"男"};
若存在同名的元素，采用最先定义的，多余的元素不会被计数
不允许nil作为键值
NSMutableDictioinary不能使用此方法，因为返回的是一个NSDictionary
2.基本操作
（1）键值对数量
（2）比较
（3）取值
（4）IO操作
1 void dicUse() 2 { 3 NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil]; 4 NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil]; 5 NSDictionary *dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys]; 6 7 NSLog(@"%@", [dic objectForKey:@"k1"]); 8 } 9 10 void dicUse2()11 {12 NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v1", @"v2", nil];13 NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil];14 NSDictionary *dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys];15 16 NSArray *keys2 = [dic allKeys];17 NSLog(@"%@", keys2);18 19 NSArray *keys3 = [dic allKeysForObject:@"v1"];20 NSLog(@"%@", keys3);21 22 23 NSArray *objs2 = [dic objectsForKeys:[NSArray arrayWithObjects:@"k1",@"k2",@"k4",nil] notFoundMarker:@"not found"];24 NSLog(@"%@", objs2);25 }
3.遍历
1 void dicLoop() 2 { 3 NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil]; 4 NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil]; 5 NSDictionary *dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys]; 6 7 //Loop all keys in dictionary 8 for (id key in dic) 9 {10 id value =http://www.mamicode.com/ [dic objectForKey:key];11 NSLog(@"%@ = %@", key, value);12 }13 }
4.迭代器
1 void dicEnumerator() 2 { 3 NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil]; 4 NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil]; 5 NSDictionary *dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys]; 6 7 //key enumerator 8 NSEnumerator *enumerator = [dic keyEnumerator]; 9 id key =nil;10 while (key = [enumerator nextObject])11 {12 id value =http://www.mamicode.com/ [dic objectForKey:key];13 NSLog(@"%@ = %@", key, value);14 }15 }
5.block迭代
1 void dicBlockLoop() 2 { 3 NSArray *objs = [NSArray arrayWithObjects:@"v1", @"v2", @"v3", nil]; 4 NSArray *keys = [NSArray arrayWithObjects:@"k1", @"k2", @"k3", nil]; 5 NSDictionary *dic = [NSDictionary dictionaryWithObjects:objs forKeys:keys]; 6 7 [dic enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) { 8 NSLog(@"%@ - %@", key, obj); 9 }];10 }
6.内存管理
1 void memoryManage() 2 { 3 Student *stu1 = [Student studentWithName:@"Simon"]; 4 Student *stu2 = [Student studentWithName:@"Joke"]; 5 Student *stu3 = [Student studentWithName:@"Man"]; 6 NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:stu1,@"stu1", 7 stu2, @"stu2", 8 stu3, @"stu3", nil]; 9 10 11 //When dictionary is destroyed, the keys & objects will be released one time12 NSLog(@"stu1 before dic release:%zi", stu1.retainCount);13 }
7.取出键、值
(1)
1 NSArray *da = [d allKeys];(2)
1 NSLog(@"%@", d[@"6"]);
8.NSDictionary是无序的，取出来的值不会按照存入的顺序排列
1 NSMutableDictionary *d = [NSMutableDictionary dictionary];2 for (int i=0; i<100; i++)3 {4 [d setObject:@"abc" forKey:[NSString stringWithFormat:@"%d", i]];5 }6 7 NSLog(@"%@", d);
out:
2014-11-19 02:36:25.850 03-NSArray[5171:303] {
0 = abc;
1 = abc;
10 = abc;
11 = abc;
0 = abc;
1 = abc;
10 = abc;
11 = abc;
...
[OC Foundation框架 - 10] NSDictionary
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