[RGSS]A Question on the attr_writer/reader/accessor[Answered]

[Shadow Eye31]

Hello there.

I recently had an issue in creating a script due to my lack of general knowledge on RGSS. I have read several articles, tutorials, guides, and topics for learning RGSS, however, I find I learn much faster if I learn in an engaged way. Merely reading an article on a function or topic does not leave the same impression a lesson or conversation would, for example. To this end, I'd like to request some help with understanding attr_writer/reader/accessor.

I recently created a script for creating custom stats which I required help with. KK20 jumped in and provided the solution:

Quote: ShowHide

It's exactly what the message window says: You don't have a 'set' method for your variables. Easy way to do that would be to make your new stats be attr_writer

attr_writer :vit

I noticed you defined your 'get' methods, so I that's why I didn't suggest attr_accessor.

Once I set the attr_writer for all of the new variables I was using, everything worked. If I held a better understanding of these functions, I feel I wouldn't have had this issue. So here I am.

I believe attr_writer/reader provide the writing/reading function to a value, respectively. However, I have little to no understanding of attr_accessor, except that perhaps it provides both of these functions. Beyond those basic statements, I haven't the foggiest impression of their function and how to effectively utilize them.

Bottom Line-
For attr_reader/writer/accessor, would someone mind going in-depth in explaining these for me?
For attr_accessor, how would this differ from using attr_reader/writer and definitions? Is it more effective?

Thank you in advance if you decide to indulge my curiosity.

[Blizzard]

Here are the equivalents for these declarations.

class A
  
  attr_writer :vit
  
  # does the same thing as attr_writer
  def vit=(value)
    @vit = value
  end
  
end

class A
  
  attr_reader :vit
  
  # does the same thing as attr_reader
  def vit
    return @vit
  end
  
end

class A
  
  attr_accessor :vit
  
  # does the same thing as attr_accessor
  def vit
    return @vit
  end
  
  def vit=(value)
    @vit = value
  end

end

[Shadow Eye31]

Thanks for helping me out a bit on this. It's good to see the comparison.

Is there a definite advantage to using one over the other? Obviously, there's less code in using a declaration, so I mean aside from that.

Thanks in advance.

[Blizzard]

Basically it's simply shorter to use attr_accessor instead of attr_writer and attr_reader separately (and your code looks cleaner).

[Shadow Eye31]

Simple enough.

So, to ensure I am understanding everything, let's say I have this code:

class Game_Actor < Game_Battler

  attr_accessor   :vit

  alias alias_setup setup
  def setup(actor_id)
    alias_setup(actor_id)
    @vit = 0
  end

end

I would be able to call, use, and rewrite vit at will in other classes? Such as below:

class Scene_Awesome

  def awesomer
     if @actor.vit <= 9000
        @actor.vit += 1
     end
  end

end

Or would I still have to make a def vit somewhere to utilize it?

I apologize for pestering you with this, and thank you for helping me thus far.

[Blizzard]

Yes, that's all you need. There is no need for any additional method definitions.

Don't worry, we're all here to help.

[Shadow Eye31]

Got it. Thank you for all your help. Its been very, well, helpful!

[Heretic86]

I'll also point out that one of the differences is for Security Purposes.  Although security isnt an issue in RMXP, if you used Ruby for a Website, you may have more need of it.

For example, SQL Injection Attacks can occur because external input isnt checked for security. 

def value=(value)
  return unless is_secure?(value)
  @value = value
end

So if you tried something like foo.value = "Erase the Database", you can check the values passed before assigning the values. 

You might also want to use some Type Checking as well.  Say you write somethign that expects a Number, and someone passes an Object to it, that can cause you trouble in the stability of your program.  You can use Get Methods to maintain your programs stability as well.

[Blizzard]

If you actually allow commands like "DROP DATABASE 'name'", then your security problem lies elsewhere. It really depends on what the purpose is of your code. If you are distributing code for systems that need to be secure or specifically designed systems and a clearly defined interface, then you need these types of checks (and you may actually be using the completely wrong language in this case as this is not what Ruby was intended for). But if you are distributing scripts that people can edit, then this stuff isn't really needed since people should be able to add their own hacks as they please.