filtering NSArray into a new NSArray in Objective-C

NSArray and NSMutableArray provide methods to filter array contents. NSArray provides filteredArrayUsingPredicate: which returns a new array containing objects in the receiver that match the specified predicate. NSMutableArray adds filterUsingPredicate: which evaluates the receiver’s content against the specified predicate and leaves only objects that match. These methods are illustrated in the following example.

NSMutableArray *array =
    [NSMutableArray arrayWithObjects:@"Bill", @"Ben", @"Chris", @"Melissa", nil];

NSPredicate *bPredicate =
    [NSPredicate predicateWithFormat:@"SELF beginswith[c] 'b'"];
NSArray *beginWithB =
    [array filteredArrayUsingPredicate:bPredicate];
// beginWithB contains { @"Bill", @"Ben" }.

NSPredicate *sPredicate =
    [NSPredicate predicateWithFormat:@"SELF contains[c] 's'"];
[array filteredArrayUsingPredicate:sPredicate];
// array now contains { @"Chris", @"Melissa" }

Assuming that your objects are all of a similar type you could add a method as a category of their base class that calls the function you're using for your criteria. Then create an NSPredicate object that refers to that method.

In some category define your method that uses your function

@implementation BaseClass (SomeCategory)
- (BOOL)myMethod {
    return someComparisonFunction(self, whatever);
}
@end

Then wherever you'll be filtering:

- (NSArray *)myFilteredObjects {
    NSPredicate *pred = [NSPredicate predicateWithFormat:@"myMethod = TRUE"];
    return [myArray filteredArrayUsingPredicate:pred];
}

Of course, if your function only compares against properties reachable from within your class it may just be easier to convert the function's conditions to a predicate string.

The Best and easy Way is to create this method And Pass Array And Value:

- (NSArray *) filter:(NSArray *)array where:(NSString *)key is:(id)value{
    NSMutableArray *temArr=[[NSMutableArray alloc] init];
    for(NSDictionary *dic in self)
        if([dic[key] isEqual:value])
            [temArr addObject:dic];
    return temArr;
}

Another category method you could use:

- (NSArray *) filteredArrayUsingBlock:(BOOL (^)(id obj))block {
    NSIndexSet *const filteredIndexes = [self indexesOfObjectsPassingTest:^BOOL (id _Nonnull obj, NSUInteger idx, BOOL *_Nonnull stop) {
                                       return block(obj);
                                   }];

    return [self objectsAtIndexes:filteredIndexes];
}