Pattern for a class that does only one thing
- by Heinzi
Let's say I have a procedure that does stuff:
void doStuff(initalParams) {
...
}
Now I discover that "doing stuff" is quite a compex operation. The procedure becomes large, I split it up into multiple smaller procedures and soon I realize that having some kind of state would be useful while doing stuff, so that I need to pass less parameters between the small procedures. So, I factor it out into its own class:
class StuffDoer {
private someInternalState;
public Start(initalParams) {
...
}
// some private helper procedures here
...
}
And then I call it like this:
new StuffDoer().Start(initialParams);
or like this:
new StuffDoer(initialParams).Start();
And this is what feels wrong. When using the .NET or Java API, I always never call new SomeApiClass().Start(...);, which makes me suspect that I'm doing it wrong. Sure, I could make StuffDoer's constructor private and add a static helper method:
public static DoStuff(initalParams) {
new StuffDoer().Start(initialParams);
}
But then I'd have a class whose external interface consists of only one static method, which also feels weird.
Hence my question: Is there a well-established pattern for this type of classes that
have only one entry point and
have no "externally recognizable" state, i.e., instance state is only required during execution of that one entry point?
