Question

RetainAll method function is in java what is alternative method in objective-C

sample code in java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class MainClass {
  public static void main(String args[]) {
    String orig[] = { "1st", "2nd", "3rd", "4th", "5th", "1st", "2nd", "3rd",
        "4th", "5th" };
    String act[] = { "2nd", "3rd", "6th" };
    List origList = new ArrayList(Arrays.asList(orig));
    List actList = Arrays.asList(act);

    System.out.println(origList.retainAll(actList));
    System.out.println(origList);
  }
}

The out put which gives 2nd 3rd 2nd 3rd

Answer 1

There isn’t a simple method for this in NSArray, but you can achieve the same effect with a predicate:

NSArray *intersectionOfArrays = [orig filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"SELF IN %@", act]];

As Tim Dean points out, this is normally an operation on sets rather than arrays, and NSSet does have methods for doing it. If your application actually could use a set here, that’s probably the best approach instead of shoehorning set behavior into an array. But if you need to keep the original ordering, you’ll have to do it with a predicate.