NSDictionary的初始化及用法

NSDictionary *dictionary=[NSDictionary dictionaryWithObject:@"aa" forKey:@"1" ];

NSLog(@"%@",dictionary);

NSDictionary *dictionary1=[NSDictionary dictionaryWithObjectsAndKeys:@"aaa",@"1", nil];

NSLog(@"%@",dictionary1);

NSDictionary *dictionary3 = @{@"1":@"a",@"2":@"aa",@"3":@"aaa"};

NSLog(@"%@",dictionary3);

NSDictionary *dictionary2=[NSDictionary dictionaryWithDictionary:dictionary];

//字典的方法：

//字典键值对的个数

NSLog(@"%zi",dictionary3.count);

//获取某一关键字的值

NSString *str = [dictionary3 objectForKey:@"2"];

NSLog(@"%@",str);

//取出所有关键对应的值

//先取出字典中所有的键，放入一个数组中，然后对这个数组便利

NSArray *arr = [dictionary3 allKeys];//取出所有的键值

for (NSString *obj in arr){

NSLog(@"%@",dictionary3[obj]);//根据键取值

}

//使用枚举器取出值

NSString *obj1;

NSEnumerator *e = [dictionary3 objectEnumerator];//获取所有value的值

while (obj1=[e nextObject]) {

NSLog(@"@@@%@",obj1);

}

//stop代表遍历停止

[dictionary3 enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {

if (stop) {

NSLog(@"key=%@,value=%@",key,obj);

}

}];