我想做的事情似乎很简单,但我在网上找不到任何答案。我有一个对象的NSMutableArray,假设它们是Person对象。我想对NSMutableArray按Person排序。birthDate是一个NSDate。

我认为这与这个方法有关:

NSArray *sortedArray = [drinkDetails sortedArrayUsingSelector:@selector(???)];

在Java中,我将使我的对象实现Comparable,或使用集合。使用内联自定义比较器排序…在Objective-C中怎么做呢?


当前回答

  let sortedUsers = users.sorted {
    $0.firstName < $1.firstName
 }

其他回答

从iOS 4开始,你也可以使用块来排序。

对于这个特殊的例子,我假设数组中的对象有一个'position'方法,它返回一个NSInteger。

NSArray *arrayToSort = where ever you get the array from... ;
NSComparisonResult (^sortBlock)(id, id) = ^(id obj1, id obj2) 
{
    if ([obj1 position] > [obj2 position]) 
    { 
        return (NSComparisonResult)NSOrderedDescending;
    }
    if ([obj1 position] < [obj2 position]) 
    {
        return (NSComparisonResult)NSOrderedAscending;
    }
    return (NSComparisonResult)NSOrderedSame;
};
NSArray *sorted = [arrayToSort sortedArrayUsingComparator:sortBlock];

注意:排序后的数组将被自动释放。

使用NSSortDescriptor对自定义对象的NSMutableArray进行排序

 NSSortDescriptor *sortingDescriptor;
 sortingDescriptor = [[NSSortDescriptor alloc] initWithKey:@"birthDate"
                                       ascending:YES];
 NSArray *sortArray = [drinkDetails sortedArrayUsingDescriptors:@[sortDescriptor]];

iOS 4块将拯救你:)

featuresArray = [[unsortedFeaturesArray sortedArrayUsingComparator: ^(id a, id b)  
{
    DMSeatFeature *first = ( DMSeatFeature* ) a;
    DMSeatFeature *second = ( DMSeatFeature* ) b;

    if ( first.quality == second.quality )
        return NSOrderedSame;
    else
    {
        if ( eSeatQualityGreen  == m_seatQuality || eSeatQualityYellowGreen == m_seatQuality || eSeatQualityDefault  == m_seatQuality )
        {
            if ( first.quality < second.quality )
                return NSOrderedAscending;
            else
                return NSOrderedDescending;
        }
        else // eSeatQualityRed || eSeatQualityYellow
        {
            if ( first.quality > second.quality )
                return NSOrderedAscending;
            else
                return NSOrderedDescending;
        } 
    }
}] retain];

http://sokol8.blogspot.com/2011/04/sorting-nsarray-with-blocks.html一点描述

-(NSMutableArray*) sortArray:(NSMutableArray *)toBeSorted 
{
  NSArray *sortedArray;
  sortedArray = [toBeSorted sortedArrayUsingComparator:^NSComparisonResult(id a, id b) 
  {
    return [a compare:b];
 }];
 return [sortedArray mutableCopy];
}

使用NSComparator进行排序

如果我们想对自定义对象进行排序,我们需要提供NSComparator,它用于比较自定义对象。该块返回一个NSComparisonResult值来表示两个对象的排序。为了对整个数组进行排序,NSComparator的用法如下。

NSArray *sortedArray = [employeesArray sortedArrayUsingComparator:^NSComparisonResult(Employee *e1, Employee *e2){
    return [e1.firstname compare:e2.firstname];    
}];

使用NSSortDescriptor进行排序 让我们假设,作为一个例子,我们有一个包含自定义类实例的数组,Employee具有属性firstname, lastname和age。下面的例子说明了如何创建一个NSSortDescriptor,该NSSortDescriptor可用于按年龄键升序对数组内容进行排序。

NSSortDescriptor *ageDescriptor = [[NSSortDescriptor alloc] initWithKey:@"age" ascending:YES];
NSArray *sortDescriptors = @[ageDescriptor];
NSArray *sortedArray = [employeesArray sortedArrayUsingDescriptors:sortDescriptors];

使用自定义比较进行排序 名称是字符串,当您对字符串进行排序以呈现给用户时,您应该始终使用本地化比较。通常您还希望执行不区分大小写的比较。下面是一个示例,使用(localizedStandardCompare:)按姓氏和名字对数组进行排序。

NSSortDescriptor *lastNameDescriptor = [[NSSortDescriptor alloc]
              initWithKey:@"lastName" ascending:YES selector:@selector(localizedStandardCompare:)];
NSSortDescriptor * firstNameDescriptor = [[NSSortDescriptor alloc]
              initWithKey:@"firstName" ascending:YES selector:@selector(localizedStandardCompare:)];
NSArray *sortDescriptors = @[lastNameDescriptor, firstNameDescriptor];
NSArray *sortedArray = [employeesArray sortedArrayUsingDescriptors:sortDescriptors];

如需参考及详细讨论,请参考: https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/SortDescriptors/Articles/Creating.html http://www.ios-blog.co.uk/tutorials/objective-c/how-to-sort-nsarray-with-custom-objects/