title: Delete an object in core data
body: <p>I have an entity in my core data model like this:</p>
  
  <pre><code>@interface Selection : NSManagedObject
  
  @property (nonatomic, retain) NSString * book_id;
  @property (nonatomic, retain) NSString * contenu;
  @property (nonatomic, retain) NSNumber * page_id;
  @property (nonatomic, retain) NSNumber * nbrOfOccurences;
  @property (nonatomic, retain) NSString * next;
  @property (nonatomic, retain) NSString * previous;
  </code></pre>
  
  <p>I have created many <code>Selection</code>s and saved them in Core Data and now I would like to delete some selections with some criteria. For example, I would like to delete a <code>Selection</code> object if matches the following:                 </p>
  
  <pre><code>content = test
  page_id = 5
  book_id = 1331313
  </code></pre>
  
  <p>How I can do this?                </p>