title: How to remove elements in NSMutableArray or NSMutableDictionary during enumeration?
body: <p>I am using block based enumeration similar to the following code:</p>
  
  <pre><code>[[[rows objectForKey:self.company.coaTypeCode] objectForKey:statementType] 
      enumerateObjectsWithOptions:NSEnumerationConcurrent 
                       usingBlock:^(id coaItem, NSUInteger idx, BOOL *stop) { 
  // block code here
  }]
  </code></pre>
  
  <p>I would like to remove some of the objects during the enumeration process depending on the their object values. </p>
  
  <p>How could I do this? I know that manipulating an mutable array or dictionary (NSMutableArray or NSMutableDictionary) during enumeration is usually not possible. </p>
  
  <p>What would be the best way to implement this?</p>
  
  <p>Thank you!</p>