iphone - NSSortDescriptor 用于比较 Cocoa/iPhone 中的 CLLocation 对象

Question

我有一个 CLLocation 对象数组，我希望能够比较它们以获取与起始 CLLocation 对象的距离。数学很简单，但我很好奇是否有一个方便的排序描述符来执行此操作？我应该避免 NSSortDescriptor 并编写自定义比较方法 + 冒泡排序吗？我通常最多比较 20 个对象，因此不需要非常高效。

Answer 1

您可以为 CLLocation 编写一个简单的compareToLocation:类别，根据自身与另一个 CLLocation 对象之间的距离返回 NSOrderedAscending、NSOrderedDescending 或 NSOrderedSame。然后简单地做这样的事情:

NSArray * mySortedDistances = [myDistancesArray sortedArrayUsingSelector:@selector(compareToLocation:)];

编辑:

像这样:

//CLLocation+DistanceComparison.h
static CLLocation * referenceLocation;
@interface CLLocation (DistanceComparison)
- (NSComparisonResult) compareToLocation:(CLLocation *)other;
@end

//CLLocation+DistanceComparison.m
@implementation CLLocation (DistanceComparison)
- (NSComparisonResult) compareToLocation:(CLLocation *)other {
  CLLocationDistance thisDistance = [self distanceFromLocation:referenceLocation];
  CLLocationDistance thatDistance = [other distanceFromLocation:referenceLocation];
  if (thisDistance < thatDistance) { return NSOrderedAscending; }
  if (thisDistance > thatDistance) { return NSOrderedDescending; }
  return NSOrderedSame;
}
@end


//somewhere else in your code
#import CLLocation+DistanceComparison.h
- (void) someMethod {
  //this is your array of CLLocations
  NSArray * distances = ...;
  referenceLocation = myStartingCLLocation;
  NSArray * mySortedDistances = [distances sortedArrayUsingSelector:@selector(compareToLocation:)];
  referenceLocation = nil;
}