按对象方法的结果对NSArray进行排序

Question

So I have an NSArray with custom objects called Church. And in each church there is an array of mass times. So there is a method in church which calculates the closest mass to the user's current time.

-(NSDate *)closestTimeTo:(NSDate *)currentTime

I want to be able to sort the NSArray of Church by the results (which are NSDate) returned by that method for each object. Basically to get a sorted list of masses sorted by the closest time and also location.

I'm using categories and can't store the closest times as properties since its a core data object. I also don't think its a good idea to save those values to core data as these methods will be called constantly due to location services.

Any ideas on how I can sort such array using the result of its objects' method?

Answer 1

Try the following block. It would help directly(or at least with minor modifications).

NSArray *sortedArray;
sortedArray = [yourArray sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
    NSDate *first = [(Church*)a closestTimeTo:currentTime];
    NSDate *second = [(Church*)b closestTimeTo:currentTime];
    return [first compare:second];
}];

Answer 2

Make a new method in your class that takes another Church class and returns NSOrderedSame , NSOrderedAscending or NSOrderedDescending , depending on whether you want that object to be first or last. Use your closestTimeTo method to find that out. Then use NSArray 's sortedArrayUsingSelector call with your method.