Remove items in a for loop without side effects?

Question

Can I remove items that I am looping through in an Objective-C for loop without side effects?

For example, is this ok?

for (id item in items) {
   if ( [item customCheck] ) {
      [items removeObject:item];   // Is this ok here?
}

Answer 1

No, you'll get an error if you mutate the array while in a fast enumeration for loop. Make a copy of the array, iterate over it, and remove from your original.

NSArray *itemsCopy = [items copy];

for (id item in itemsCopy) {
   if ( [item customCheck] )
      [items removeObject:item];   // Is this ok here
}

[itemsCopy release];