遍历字典遍历的是key而不是value!!!

最近项目中需要遍历字典筛选有用信息,在遍历时遇到一些崩溃,猛然醒悟,虽不值一提,可也是个知识点,记录一下.

NSDictionary * dic = @{@"student":@[@"jim"], @"score":@[@"80"], @"ages":@[@"18", @"20", @"24"]};
    for (id string in dic) {
        NSLog(@"string = %@", string);
    }

结果为:

string = score
 string = ages
 string = student

二如果你直接用了value的值

NSDictionary * dic = @{@"student":@[@"jim"], @"score":@[@"80"], @"ages":@[@"18", @"20", @"24"]};
    for (id string in dic) {
        NSLog(@"string = %@", string[0]);
    }

则会抛出异常:

-[__NSCFConstantString objectAtIndexedSubscript:]: unrecognized selector sent to instance 0x335a4c

意思是说本该是字符串的对象,却调用objectAtIndex方法,抛出异常.正确的方法是:

for (id string in dic) {
        id value = dic[string];
        NSLog(@"value = %@", value);
    }