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Re: Moose n00b question about writer / reader

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From:
Buddy Burden
Date:
April 20, 2015 00:37
Subject:
Re: Moose n00b question about writer / reader
Message ID:
55344A5E.5000804@gmail.com
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. :-)

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