对包含NSMutableDictionaries

Question

我试图找出对包含n个字典的数组进行排序的最佳/最有效方法。每个字典中的一个键/值对是日期字段。将所有字典添加到数组后，我想按降序排列数组。

例如，我有这样的代码：

NSMutableArray *myArray = [[NSMutableArray alloc] init];

NSMutableDictionary *dictionary1 = [[NSMutableDictionary alloc] init];
    NSDate *today = [NSDate date];
    [dictionary1 setObject:today forKey:@"date"];
    [dictionary1 setObject:@"Another value" forKey:@"anotherKey"];

[myArray addObject:dictionary1];

NSMutableDictionary *dictionary2 = [[NSMutableDictionary alloc] init];
    NSDate *tomorrow = [[NSDate date] dateByAddingTimeInterval:60*60*24];
    [dictionary2 setObject:tomorrow forKey:@"date"];
    [dictionary2 setObject:@"Yet another value" forKey:@"anotherKey"];

[myArray addObject:dictionary2];

现在我需要按降序日期对myArray进行排序。 （数组索引0应该是最新日期）

注意：在我的实际项目中，我没有以这种方式创建和添加词典。但是，例如，为了查看日期如何存储在字典中，我们假设我已将这两个放入数组中。

Answer 1

您可以在此处使用NSSortDescriptors：

NSMutableArray *myArray = [[NSMutableArray alloc] init];

NSMutableDictionary *dictionary1 = [[NSMutableDictionary alloc] init];
NSDate *today = [NSDate date];
[dictionary1 setObject:today forKey:@"date"];
[dictionary1 setObject:@"Another value" forKey:@"anotherKey"];

[myArray addObject:dictionary1];

NSMutableDictionary *dictionary2 = [[NSMutableDictionary alloc] init];
NSDate *tomorrow = [[NSDate date] dateByAddingTimeInterval:60*60*24];
[dictionary2 setObject:tomorrow forKey:@"date"];
[dictionary2 setObject:@"Yet another value" forKey:@"anotherKey"];

[myArray addObject:dictionary2];

NSSortDescriptor *sortDesciptor = [NSSortDescriptor sortDescriptorWithKey:@"date" ascending:NO];

//Create new sorted array
NSArray *sortedArray = [myArray sortedArrayUsingDescriptors:@[sortDesciptor]];

//Or sort your mutable one
[myArray sortUsingDescriptors:@[sortDesciptor]];

Answer 2

有很多方法可以做到这一点。您可以使用NSSortDescriptor，如Krivoblotsky所说。

您还可以使用#!/usr/bin/env ruby h, m, s = 12, 07, 13 $_.gsub!(/(\d\d):(\d\d):(\d\d)/) do hour, min, sec = [ $1.to_i + h, $2.to_i + m, $3.to_i + s ] if sec >= 60 then min += 1; sec -=60; end #only needed if s > 0 if min >= 60 then hr += 1; min -=60; end #must do before seconds offset '%02d:%02d:%02d' % [hour, min, sec] end NSMutableArray方法。代码看起来像这样：

sortUsingComparator

[myArray sortUsingComparator ^(NSDictionary *obj1, NSDictionary *obj2) { return [obj1["date"] compare: obj2["date"]] } ]; 方法需要sortUsingComparator块。

NSComparator接受两个id类型的对象，并返回NSComparator：

NSComparisionResult

由于NSDate支持compare方法，你可以编写1行比较器块来获取每个字典的日期条目，并返回比较它们的结果。