Question: What I want to do seems pretty simple, but I can't find any answers on the web. I have an NSMutableArray of objects, let's say they are 'Person' objects. I want to sort the NSMutable array by Person.birthDate which is an NSDate.
1. Either you implement a compare-method for your object:
- (NSComparisonResult)compare:(Person *)otherObject {
return [self.birthDate compare:otherObject.birthDate];
}
NSArray *sortedArray = [drinkDetails sortedArrayUsingSelector:@selector(compare:)];
2. or usually even better: (The default sorting selector of NSSortDescriptor is compare:)
NSSortDescriptor *sortDescriptor;
sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"birthDate"
ascending:YES] autorelease];
NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor];
NSArray *sortedArray;
sortedArray = [drinkDetails sortedArrayUsingDescriptors:sortDescriptors];
NSComparisonResult compare(Person *firstPerson, Person *secondPerson, void *context) {
if ([firstPerson birthDate] < [secondPerson birthDate])
return NSOrderedAscending;
else if ([firstPerson birthDate] > [secondPerson birthDate])
return NSOrderedDescending;
else
return NSOrderedSame;
}
int SortPlays(id a, id b, void* context) {
Play* p1=a;
Play* p2=b;
if (p1.score<p2.score) return NSOrderedDescending;
else if (p1.score>p2.score) return NSOrderedAscending;
return NSOrderedSame;
}
...
[validPlays sortUsingFunction:SortPlays context:nil];
4. Starting in iOS 4 you can also use blocks for sorting.
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];
featuresArray = [unsortedFeaturesArray sortedArrayUsingComparator: ^(id a, id b){ ... }]
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