ios - 从多维 NSDictionary 的子字典值创建排序数组

Question

我有一个包含子 NSDictionaries 的 NSDictionary，我想知道是否可以通过子词典的“name”键的值按字母顺序对主词典进行排序。

NSDictionary *student1 = @{@"first_name" : @"Scott", @"last_name" : @"Smith"};
NSDictionary *student2 = @{@"first_name" : @"John", @"last_name" : @"Donalson"};
NSDictionary *student3 = @{@"first_name" : @"Mary", @"last_name" : @"Patricia"};
NSDictionary *student4 = @{@"first_name" : @"Zack", @"last_name" : @"Elliot"};

NSDictionary *students = @{"001": student1, "002": student2, "003": student3, "004": student4};

我希望能够创建一个数组或可变数组，它只保存键，但根据子字典中某些键的值进行排序。像这样:

姓氏数组

["002", "004", "003", "001"];

名字数组

["002", "003", "001", "004"];

Answer 1

查看 NSDictionary 方法keysSortedByValueUsingComparator:

您提供一个比较器 block ，用于处理值(您的学生词典)并返回一个键数组。

https://developer.apple.com/library/ios/documentation/cocoa/reference/foundation/Classes/NSDictionary_Class/Reference/Reference.html#//apple_ref/doc/uid/20000140-SW21