Subtract an array of complex objects from another array of same kind of objects ios

Question

I know that subtracting an NSArray from NSArray if it is a single basic object found here

But what i have is an object like this

@interface Set : NSObject
@property (nonatomic, strong) NSString *ItemId;
@property (nonatomic, strong) NSString *time;
@property (nonatomic, strong) NSString *Category_id;
@property (nonatomic, strong) NSString *List_id;
@property (nonatomic, strong) NSString *name;
@end

How can i delete an array having the set object from another array with the same? It can be done by iterations that i knw.Is there some other way ?

EDIT: For clarity

I have Array A with 5 Set objects and I have 4 Set Objects in Array B array A and Array B contain 3 set objects with common values..[Note : memory may be different] common

All I need is an Array C =Array A - Array B that has 2 objects in resulting array C

Thank You :)

[Remove duplicate objects from an NSMutableArray](http://stackoverflow.com/q/6518714/1603234) and check *micpringle* answer. — Hemang, Feb 21 '13 at 06:33
Checked it says that it is about removing duplicate by comparing and itrating in a loop...I knew that way.Is there some other method? — Lithu T.V, Feb 21 '13 at 06:40
let me understand... You have 2 arrays arr1 and arr2, both having objects of `Set`. You want to find `resultArr=arr1-arr2`. is it? — Anoop Vaidya, Feb 21 '13 at 06:48
@LithuT.V, Check my answer. It does the same thing. But note that under the hood it will be still enumerating objects. You cant avoid that. — iDev, Feb 21 '13 at 06:59

iDev · Answer 1 · 2013-02-21T06:56:24.613

You need to implement the - (NSUInteger)hash and - (BOOL)isEqual:(id)object method in Set class.

For eg:-

- (NSUInteger)hash {
   return [self.ItemId hash];
}

- (BOOL)isEqual:(id)object
{
    return ([object isKindOfClass:[self class]] &&
            [[object ItemId] isEqual:_ItemId])

}

After that try this:

NSMutableSet *set1 = [NSMutableSet setWithArray:array1];
NSMutableSet *set2 = [NSMutableSet setWithArray:array2];
[set1 intersectSet:set2]; //this will give you only the obejcts that are in both sets

NSArray *commonItems = [set1 allObjects];

[mutableArray1 removeObjectsInArray:commonItems];//mutableArray1 is the mutable copy of array1

mutableArray1 will have all objects in the same order as earlier after removing common objects.

βhargavḯ · Answer 2 · 2013-02-21T07:34:23.093

By using NSSet and NSPredicate we can meet your requirement.

Assessors *ass1 = [[Assessors alloc] init];
ass1.AssessorID = @"3";

Assessors *ass2 = [[Assessors alloc] init];
ass2.AssessorID = @"2";

Assessors *ass3 = [[Assessors alloc] init];
ass3.AssessorID = @"1";

Assessors *ass4 = [[Assessors alloc] init];
ass4.AssessorID = @"2";

NSSet *nsset1 = [NSSet setWithObjects:ass1, ass2,  nil];
NSSet *nsset2 = [NSSet setWithObjects:ass3, ass4, nil];

// retrieve the IDs of the objects in nsset2
NSSet *nsset2_ids = [nsset2 valueForKey:@"AssessorID"];

// only keep the objects of nsset1 whose 'id' are not in nsset2_ids
NSSet *nsset1_minus_nsset2 = [nsset1 filteredSetUsingPredicate:[NSPredicate predicateWithFormat:@"NOT AssessorID IN %@",nsset2_ids]];

for(Assessors *a in nsset1_minus_nsset2)
    NSLog(@"Unique ID : %@",a.AssessorID);

Here Assessors is my NSObject Class (Set in your case) and AssessorID is one property of that class.

Hope this can help.

Subtract an array of complex objects from another array of same kind of objects ios

2 Answers2