如何排序最近距离的对象数组（经度，纬度）？ [英] How to sort array of objects(latitude, longitude) by nearest distance?

问题描述

我已经从核心数据数组，我试图想我怎么可以在最近距离对数组进行排序：

 的for（int i = 0; I＆LT; allTask​​s.count;我++）{
        ID singleTask = allTask​​s [I]
        双纬度= [singleTask [@纬度]的doubleValue];
        双经度= [singleTask [@经度]的doubleValue];
    }
 

编辑：
当前位置和阵列中的所有位置之间的距离。
我知道如何计算距离，我不知道如何对它们进行排序。

解决方案

1. 得到您的currentPosition的CLLocation（这是通过CLLocationManager完成）




2. 计算每个项目，并保存距离+项目在字典一对距离




3. 排序字典allKeys阵列比较：选择

所以

  CLLocation *电流= ...;
*的NSMutableDictionary distsAndTasks [字典的NSMutableDictionary];对（在allTask​​s ID任务）{
    CLLocation * taskLoc = [[CLLocation页头] initWithLatitude：task.lat经度：task.long]; //！
    CLLocationDistance DIST = [taskLoc distanceFrom：当前];
    如果（distsAndTasks [@（DIST）]）{
        NSMutableArray里* equidstants = [distsAndTasks [@（DIST）mutableCopy]
        [equidstants ADDOBJECT：任务];
        distsAndTasks [@（DIST）] = equidstants;
    }
    其他{
        distsAndTasks [@（DIST）] = @ [任务];
    }
}NSArray的* sortedDists = [distsAndTasks.allKeys sortedArrayUsingSelector @选择器（比较:)//任务现在可以在一个有序的方式访问
对（在sortedDists的NSNumber * DIST）{
    NSArray的* tasksAtDistance = distsAndTasks [测距]
    的NSLog（@％@，tasksAtDistance）;
}
 

I've an array from core data and I'm trying to think how can I sort the array by the nearest distance:

for (int i=0; i<allTasks.count; i++) {
        id singleTask = allTasks[i];
        double latitude = [singleTask[@"latitude"] doubleValue];
        double longitude = [singleTask[@"longitude"] doubleValue];
    }

EDIT: The distance between current location and all the locations in the array. I know how to calculate the distance, I don't know how to sort them.

解决方案

1. get the CLLocation for your currentPosition (this is done via CLLocationManager)

2. calculate the distances for each item and store distance+item as a Pair in a Dictionary

3. Sort Dictionary allKeys array with compare: selector

so

CLLocation *current = ...;
NSMutableDictionary *distsAndTasks [NSMutableDictionary dictionary];

for(id task in allTasks) {
    CLLocation *taskLoc = [[CLLocation alloc] initWithLatitude:task.lat longitude:task.long];//!
    CLLocationDistance dist = [taskLoc distanceFrom:current];
    if(distsAndTasks[@(dist)]) {
        NSMutableArray *equidstants = [distsAndTasks[@(dist)] mutableCopy];
        [equidstants addObject:task]; 
        distsAndTasks[@(dist)] = equidstants; 
    }
    else {
        distsAndTasks[@(dist)] = @[task]; 
    }
}

NSArray *sortedDists = [distsAndTasks.allKeys sortedArrayUsingSelector@selector(compare:)

//the tasks can now be access in a sorted way
for(NSNumber *dist in sortedDists) {
    NSArray *tasksAtDistance = distsAndTasks[dist];
    NSLog(@"%@", tasksAtDistance);
}

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