Andrew,
I want to create a class that has some attributes. However, there’s
some logic that needs to be executed when setting values on these
attributes. In some cases, I’ll need to throw an error like “you can’t
set that value on this object attribute”, I also need to be able to
modify the value on the way into the object sort of like a DECODE()
statement in SQL, etc.
You'll want to scroll half a dozen screenfuls downward on the same page
and check out the section titled "Triggers". These can be used to do
exactly the things you want.
Setting writer / reader, on the other hand, is just providing names to
the accessor routines which Moose creates automatically for you.
Harald is absolutely correct. I don't know if this will help or not,
but here's how I think of it.
In Moose, just as in C++,[1] there's a distinction between
initialization and assignment. When you call a constructor, you're
initializing the attributes. When you call a mutator,[2] you're
assigning to an attribute. A trigger is a way to hook into to both
methods of setting the attribute.[3]
And, if that _doesn't_ help, feel free to ignore me. :-)
-- Buddy
[1] And maybe in other OO languages as well (Java, perhaps?).
[2] What we generally call an accessor. But, if your attribute is rw,
then it's technically a mutator.
[3] C++ doesn't have such a thing. Yet another reason I prefer Moose. :-)
