LimitIterator::key

参见

• LimitIterator::getPosition() - Return the current position
• LimitIterator::current() - Get current element
• LimitIterator::next() - Move the iterator forward
• LimitIterator::rewind() - Rewind the iterator to the specified starting offset
• LimitIterator::seek() - Seek to the given position
• LimitIterator::valid() - Check whether the current element is valid