Filter a NSMutableArray of objects and copy to a new NSArray

Question

I have a NSObject defined with a few properties and to keep this question simple, let's say the object is called Vehicle and there are three properties: Manufacturer, Model, Year.

I read all vehicles from a database and the result is a NSMutableArray of Vehicle objects.

I am trying to create a new array of vehicles that are filtered by manufacturer where the object = "Ford".

Is the correct approach:

NSPredicate *fordMotorCarsPredicate = [NSPredicate predicateWithFormat:@"ANY   Vehicle.Manufacturer = %@", @"Ford"];

fordMotorCarsArray = [listOfVehicles filteredArrayUsingPredicate:fordMotorCarsPredicate];

I know I could filter the list using an SQL query, but I'd like to know whether this can be achieved in Objective-C code.

Any ideas? Cheers, Ross.

possible duplicate of [Using NSPredicate to filter an NSArray based on NSDictionary keys](http://stackoverflow.com/questions/958622/using-nspredicate-to-filter-an-nsarray-based-on-nsdictionary-keys) — Maurício Linhares, Sep 16 '11 at 12:28

score 2 · Accepted Answer · answered Sep 16 '11 at 12:30

2

If each object in the mutable array has a manufacturer property then predicate should be

 [NSPredicate predicateWithFormat:@"manufacturer = %@", @"Ford"];

answered Sep 16 '11 at 12:30

diederikh

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Thanks. This is the easiest solution. Appreciate all the other answers. – rosst400 Sep 17 '11 at 04:45

score 1 · Answer 2 · answered Sep 16 '11 at 12:42

You can use a predicate only if the underlying objects are KVC-compliant for the key you are testing against. But that condition is actually a weak condition. It's enough for example to have a property by that name.

Now you can always filter your array manually:

- (NSMutableArray *) cars:(NSArray *)listOfVehicles builtBuy:(NSString*)manufacturer {
    NSMutableArray *resultCars = [[NSMutableArray alloc] init];
    for (Car *aCar in listOfVehicles) {
        if ([manufacturer isEqualToString:aCar.Manufacturer]) {
            [resultCars addObject:aCar];
        }
    }
    return [resultCars autorelease];
}

score 0 · Answer 3 · answered Sep 16 '11 at 12:33

Ther is an alternative to NSPredicat but i'm not sure it's worth it in your case... sow this is how you sort an array alfabetically,

somearray =[[NSMutableArray alloc] initWithArray:an array]; 

     NSSortDescriptor *sortDescriptor;
     sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"Vehicle" ascending:YES] autorelease];
     [somearray sortUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]];

however if you need a more specific sorting you can add a selector to the sort descriptor that will hold the logic of the sorting like this

NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"Vehicle" ascending:NO selector:@selector(VehicleSortingLogic:)];

I never used it with a selector before but it should work , hope this helps

Filter a NSMutableArray of objects and copy to a new NSArray

3 Answers3