title: Use NSPredicate for matching id's in two arrays
body: <p>Hello i have a maybe easy question but i cant handle it yet.</p>
  
  <ul>
  <li>I have a Modelclass 'Location' which holds an Array with Category ID's (12, 23, 56).</li>
  <li>Then i have an Array with all available Category ID's (1,2,3,4,5,6,7,...)</li>
  <li>All this Categories have an ID are shown in a TableView and are able to select or not.</li>
  <li>I show a punch of Markers on a MapView (Annotation Class is Location) which should be shown based on the selection of the filters in the mentioned Filter TableView.</li>
  </ul>
  
  <p>I need to implement a "Filter by Category" function which removes all markers and add them again but just based on the selection in the list.</p>
  
  <p>So i need to compare the array with the filter-id's in the Location Model with the Array with all the Filter-ID's in the TableView. i used the following function for this:</p>
  
  <pre><code>for (Location *currLocation in arrListOfLocationsNearby) {
  </code></pre>
  
  <p>for (NSString *currKatId in currLocation.arrKatIds) {</p>
  
  <pre><code>NSInteger intCurrKatId = [currKatId integerValue];
  NSLog(@"Current KatId %@ id: %d \n", currLocation.strAdr, intCurrKatId);
  
  for (Filter *currFilter in [SDM getSharedDataManager].arrListOfFilterOptions) {
  
   if (currFilter.isSelected) {
  
    NSInteger intCurrFilterId = [currFilter.strAtt_id intValue];
    NSLog(@"Current Filter %@ id: %d \n", currFilter.strAtt_text, intCurrFilterId);
  
    if ([currKatId intValue] == [currFilter.strAtt_id intValue]) {
     currLocation.isVisible = YES;
    }else {
     currLocation.isVisible = NO;
    }
   }
  }
  </code></pre>
  
  <p>}
    }</p>
  
  <p>I know this will be the most ineffective way to loop through everything. I want to use somehow NSPredicate for this but i never used them before and i can't find examples for my problem.</p>
  
  <p>Any Hints from you guys?</p>
  
  <p>regards m.</p>