2 MVC Variations
Traditional MVC is excellent as a starting point for discussion, but by no means it must be considered the one and only proper way of doing MVC. In fact, we saw how Traditional MVC is outdated within the context of modern UI development. New patterns have emerged, built around fundamental MVC concepts and nomenclature, but with additional tricks, extensions and alternative design choices to shorten development time and satisfy modern UI requirements, such as the following:
- a modal dialog must allow changing values, but revert them when the Cancel button is pressed.
- a modeless dialog allows changing values while the change is visible in another window, but must be reverted if “Restore” is pressed.
- prevent typing of invalid values, for example a string in a line edit supposed to accept only digits will not accept any key presses from non-digits.
- alternatively, allow invalid entries, but disable the Ok button and mark the incorrect value red.
- and so on…
As you can see, the complexity of an application made of hundreds of menus, text input areas and buttons, plus all the possible logical dependencies among them can grow considerably. Unexpected interactions and strange communication patterns emerge in the form of bugs or application freezes. Keeping this communication network well organized and confined by enforcing a structure is of paramount importance.
Design aims at managing complexity. The MVC details given in this book are guidelines, but need to consider the actual real problem at hand. Some flexibility is needed. Strict compliance generally produces a benefit, and has better communicative consistency within the development team, but may not always be appropriate for specific cases. In that case, reconsider the design, or relax some constraints, but aim at keeping logic encapsulated and object interaction simple and straightforward.
In this chapter we will examine alternative design in MVC able to deal with more complex use-case scenarios, constrained by requirements, architectural needs or self-documentation purposes.