The Rewindable Entity Iterator

Our EntityIterators are composed of a standard PDO PreparedStatement and a DataMapper. The DataMapper maps rows into objects in real time as we iterate over the the Statement. There is a limitation with PDO Statements in that you can only iterate over them one time.

For example:

// first loop works fine
foreach($statement as $result) {
    // do something with result
}

// but subsequent loops don't
foreach($statement as $result) {
    // never called 
}

Since our EntityIterator operates by iterating over the statement it can also only be looped over once. This causes all sorts of problems.

Your Job

Derive a RewindableEntityIterator from the EntityIterator class. Your new iterator should be rewindable and thus able to iterate over its elements repeatedly. To simplify the task we have used a ResultSet object instead of a PDO Statement. The EntityIterator iterates over the ResultSet object directly. Like the PDO Statement, the ResultSet does not have the ability to rewind.

A few constraints and notes

• Implement the RewindableEntityIterator class in the src directory
• Do not alter any other files in the src directory
• There are quite a few corner cases to consider
• There is a PHPUnit test file in the tests directory - add additional tests if it's helpful to you.
• Be conscious of time & space complexity

Good luck