Custom QValidator

This is an example of a custom QValidator written as an answer on this stackoverflow question.

The validator excepts the following inputs:

1. dddd
2. dddd-dddd

where in the second case the right hand side (rhs) must be bigger than the left hand side (lhs).

Acceptable inputs:

• 1234
• 1234-5678
• 9998-9999

Invalid inputs:

• 123
• 1234-23
• 1234-1234