Compare two arrays and put equal objects into a new array

Question

How can I compare two NSArrays and put equal objects into a new array?

What is the type of the objects in your arrays? You want compare the object's value or just the object(the reference) itself? — EmptyStack, Aug 29 '11 at 10:47
both arrays contains strings, I want to put common strings to a new array — smartsanja, Aug 29 '11 at 10:55
Alright. Try this solution. http://stackoverflow.com/questions/7207805/getting-unique-numbers-from-two-arrays/7207883#7207883 — EmptyStack, Aug 29 '11 at 10:58
@Vijay — you copied your own answer and you link to it. Wouldn't be one enough? — vikingosegundo, Aug 29 '11 at 11:17
@viking just now i answered for both of them.by read from his comments i realize that he has nsstring in both.so that i have route him to that link.but before that i had thought any object he wants.nothing else — Vijay-Apple-Dev.blogspot.com, Aug 29 '11 at 11:21
have a look at this: http://stackoverflow.com/questions/6023548/finding-intersection-of-nsmutablearrays/6023588#6023588 same approach as EmptyStack, but gives intersection of the given arrays. — vikingosegundo, Aug 29 '11 at 11:22

score 6 · Accepted Answer · answered Aug 29 '11 at 10:57

NSArray *array1 = [[NSArray alloc] initWithObjects:@"a",@"b",@"c",nil];
    NSArray *array2 = [[NSArray alloc] initWithObjects:@"a",@"d",@"c",nil];
    NSMutableArray *ary_result = [[NSMutableArray alloc] init];
    for(int i = 0;i<[array1 count];i++)
    {
        for(int j= 0;j<[array2 count];j++)
        {
            if([[array1 objectAtIndex:i] isEqualToString:[array2 objectAtIndex:j]])
            {
                [ary_result addObject:[array1 objectAtIndex:i]];
                break;
            }
        }
    }
    NSLog(@"%@",ary_result);//it will print a,c

score 2 · Answer 2 · answered Aug 29 '11 at 10:55

Answer:

NSArray *firstArr, *secondArr;
// init arrays here
NSMutableArray *intersection = [NSMutableArray array];
for (id firstEl in firstArr)
{
    for (id secondEl in secondArr)
    {
        if (firstEl == secondEl) [intersection addObject:secondEl];
    }
}
// intersection contains equal objects

Objects will be compared using method compare:. If you want to use another method, then just replace if (firstEl == secondEl) with yourComparator that will return YES to equal objects: if ([firstEl yourComparator:secondEl])

@narayana, thanks a lot guys, I was able to solve it using if([[array1 objectAtIndex:i] isEqualToString:[array2 objectAtIndex:j]] — smartsanja, Aug 29 '11 at 11:15

score 1 · Answer 3 · edited May 23 '17 at 12:14

//i assume u have first and second array with objects

//NSMutableArray *first = [ [ NSMutableArray alloc]init];

//NSMutableArray *second = [ [ NSMutableArray alloc]init];                             

NSMutableArray *third = [ [ NSMutableArray alloc]init];


    for (id obj in first) {

        if ([second  containsObject:obj] ) {


            [third addObject:obj];

        }


    }


NSLog(@"third is : %@ \n\n",third);


more over if u have strings in both array then look at this answer of mine

Finding Intersection of NSMutableArrays

Compare two arrays and put equal objects into a new array

3 Answers3

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