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Make your objects immutable by default

More about the Good DojoIn my post last week, I discussed creating objects that are instantiated safely. Please go back and read if you are interested. At the end of the post, I mentioned that I'd also written the class so it was immutable when instantiated. This is important!!! I feel like a broken record in repeating this but I am sure at the time of writing your code, you aren't modifying your object all over the place and so are safe in the belief that protecting against mutability is overkill. Please remember though, your code could be around for a hell of a long time. You aren't writing your code for now...you are writing for the next fool that comes along (including you). Nothing is more upsetting that coming back to fix a bug on some wonderfully crafted code to say "Who has butchered my code?!", but often you were involved at the start of the process. You made the code easy to modify, allowing objects to be used / reused / modified without thinking o…

An instantiated object should be "ok"

I've been QA'ing quite a bit of work recently and one common theme I've noticed across both Java and C# projects I have been looking at is that we occasionally open ourselves up unessacarily to Exceptions by the way objects are being created.

My general rule of thumb (which I have seen mentioned in a Pluralsight video recently but also always re-iterate in various Robust Software talks I have done) is that you shouldn't be able to create an object and then call a method or access a property that then throws an exception. At worst, it should return null (I'm not going to moan about that now).

I've created an example below. We have two Dojos, one is good and one is bad. The bad dojo looks very familiar though. It's a little class written in the style that seems often encouraged. In fact, many classes start life as something like this. Then as years go on, you and other colleagues add more features to the class and it's instantiation becomes a second cl…