template

All posts tagged template

Default Implementations Using Delegation

Posted by Jacob Zimmerman on 2017-01-07
Posted in: Design Patterns, Kotlin, Python. Tagged: , , . Leave a comment

Hey everyone! It’s my first post of the new year! Usually, I do a bunch of book reviews at the beginning of the year, and I will certainly do that in upcoming posts. UPDATE: No, I won’t. Not this year. Sorry.

Also, don’t worry that I may have given up on my video series; I haven’t. I’m simply being a moron and doing other, less important things in my free time. I’m sure I’ll whip myself into shape soon enough.

Lastly, I’ve received a bunch of free copies of my book from Apress, so I’ll be coming up with some way to give those away sometime soon.

Onto THIS article now.

Intro

I need to start this article with a disclaimer: this isn’t really even a good idea. It’s really just a thought experiment that I did, and I’d like to show you how it could be done if you ever wanted to do it. Continue Reading

The Clash of Template and Delegate Patterns

Posted by Jacob Zimmerman on 2015-06-20
Posted in: Design Patterns, Python, Refactoring. Tagged: , , , , . Leave a comment

Back in my delegate decorator article, I mentioned some weaknesses of the delegate pattern as a substitute to inheritance. The decorator solved one of those problems, but the other is still a problem. The problem comes when using something akin to the template pattern. Continue Reading

Replacing Inheritance with Composition

Posted by Jacob Zimmerman on 2015-05-09
Posted in: Design Patterns, General Practices, Java, Kotlin, Refactoring. Tagged: , , , , , , , . 4 Comments

Quite a while back, I posted about how, despite the fact that you should prefer composition over inheritance, you can best design classes for inheritance. Now, I wish to give some examples of how you can take your code that uses inheritance and change it to use composition instead, which will often actually make your code more flexible.

The code will be in java, but the concepts can transferred to any language that is object-oriented. Some languages might have constructs that make parts of this easier, too (Kotlin’s Delegates).

One thing is important to remember, though: Even if you switch “completely” to composition, you will still have some inheritance. This inheritance will be from interfaces and interface-like classes only, though. It barely counts as inheritance, really, since all it’s doing is restricting itself to an API and not inheriting implementation details. Continue Reading

Designing Classes for Extension

Posted by Jacob Zimmerman on 2014-12-06
Posted in: Design Patterns, General Practices, Java. Tagged: , . 2 Comments

Intro

In Effective Java by Joshua Bloch, it is explained that if you create a class, you should “design and document for inheritance or else prohibit it” (item 17). It gives some very good advice about making classes to be extended, but I always felt it lacking in patterns for doing so. I highly recommend Effective Java to any Java programmer, as it has good tips for just about every level of Java programmer (other than maybe a super expert).

I would dig into the tips that he provides, but that would be invading on his great work, and it would probably make my article too long for my liking. Continue Reading