[radicalbyte]

> The principles, however, can easily lead to more manageable or coherent code over time.

This. 1000 times over. This is why well factored code bases can often seem to have lots of redundant classes and interfaces to inexperienced developers. It's all about maintainability over time, building bulkheads around change.

> tools that generated the right code—interface builders for example

The irony is that these tools often fail when the benefit is considered over time. This comes through a lack of tools - their code works badly with SCM (no domain-specific diff tools). They throw away everything we've learnt about software engineering just to win the marketing demo's.

[codygman]

How do redundant classes and interfaces improve maintainability over time?

[muhuk]

Because they improve maintainability, they are not redundant.

[codygman]

I asked how redundant classes and interfaces improve maintainability over time.

I'll narrow down my question some more:

How does duplicated code improve maintainability over time?

[hakunin]

Author stated that classes and interfaces seem redundant, not actually redundant. Repeated code could improve maintainability because it may actually have different reasons to change, and only look similar on the surface. I've seen this often missed by inexperienced devs who get overzealous trying to DRY up everything.