How to sort NSMutableArray

Question

my class:

car -------------- price color 

I created an NSMutableArray that contains several of these car objects, how to sort NSMutableArray by price

Answer 1

Using a comparator , it might look like this:

 NSMutableArray *cars= [NSMutableArray arrayWithCapacity:5]; [cars addObject:[[[Car alloc] initWithColor:@"blue" price:30000.0] autorelease]]; [cars addObject:[[[Car alloc] initWithColor:@"yellow" price:35000.0] autorelease]]; [cars addObject:[[[Car alloc] initWithColor:@"black" price:29000.0] autorelease]]; [cars addObject:[[[Car alloc] initWithColor:@"green" price:42000.0] autorelease]]; [cars addObject:[[[Car alloc] initWithColor:@"white" price:5000.0] autorelease]]; [cars sortUsingComparator:^NSComparisonResult(Car *car1, Car *car2) { if (car1.price < car2.price) return (NSComparisonResult)NSOrderedAscending; if (car1.price > car2.price) return (NSComparisonResult)NSOrderedDescending; return (NSComparisonResult)NSOrderedSame; }]; NSLog(@"%@", cars); 

And this is my Car class:

 @interface Car : NSObject @property (nonatomic, copy)NSString *colorName; @property (nonatomic) float price; -(id)initWithColor:(NSString *)colorName price:(float)price; @end @implementation Car @synthesize colorName = colorName_; @synthesize price = price_; -(id)initWithColor:(NSString *)colorName price:(float)price { if (self = [super init]) { colorName_ = [colorName copy]; price_ = price; } return self; } - (void)dealloc { [colorName_ release]; [super dealloc]; } -(NSString *)description { return [NSString stringWithFormat:@"%@ %f", self.colorName, self.price]; } @end 

Answer 2

Using sortUsingComparator or sortUsingFunction messages in class .

Answer 3

Array sorting has a built-in cistern that you must use because of the fast enumeration. For dictionary keys, I use a bubble view similar to this:

 - (NSMutableArray*) bubbleSortDictKeys:(NSDictionary*)dict { if(!dict) return nil; NSMutableArray *sortedKeys = [NSMutableArray arrayWithArray: [dict allKeys]]; if([sortedKeys count] <= 0) return nil; else if([sortedKeys count] == 1) return sortedKeys; int n = [sortedKeys count] -1, i; BOOL swapped = YES; NSString *key1,*key2; NSComparisonResult result; while(swapped) { swapped = NO; for( i = 0; i < n; i++ ) { key1 = [sortedKeys objectAtIndex: i]; key2 = [sortedKeys objectAtIndex: i + 1]; result = [key1 compare: key2 options: NSCaseInsensitiveSearch]; if(result == NSOrderedDescending) { [key1 retain]; [key2 retain]; [sortedKeys exchangeObjectAtIndex:i withObjectAtIndex:i+1]; [key1 release]; [key2 release]; swapped = YES; } } } return sortedKeys; } 

Then you can use this function as follows:

 NSEnumerator *keys = [[self bubbleSortDictKeys:dict] objectEnumerator]; 

For reference, a list of built-in methods for sorting arrays is provided:

• sortedArrayHint
• sortedArrayUsingFunction: context:
• sortedArrayUsingFunction: context: tooltip:
• sortedArrayUsingDescriptors:
• sortedArrayUsingSelector:
• sortedArrayUsingComparator:
• sortedArrayWithOptions: usingComparator:

For completeness, in response to my comment below, you will learn how to use the sort descriptor for a key dictionary or any array:

 NSArray *arrayToSort, *sortedArray; arrayToSort = [NSArray arrayWithObjects:car1, car2, car3, nil]; NSSortDescriptor *descriptor = [[NSSortDescriptor alloc] initWithKey:@"color" ascending:YES]; sortedArray = [arrayToSort sortedArrayUsingDescriptors:[NSArray arrayWithObject:descriptor]]; // Use your sortedArray 

Enjoy.