Redefining operators like += and -= for certain objects?

[Kain Nobel]

Good day everybody!

After updating certain scripts, there's something in my personal Window Movable module that I've always wanted to do. Now, to move a window, I can use either of these commands, which do the same thing (then 'update' recalls the method continuously until the self.x == @new_x)

@window.x_to(320)
@window.new_x = 320

But then, I've created other methods like x_plus and x_minus, which is something like this

def x_plus(n)
  @new_x = self.x + n
end

But, what if I wanted to enhance the @new_x (or @new_y or whatever) so that I could do the same thing via...

@window.new_x += 320 # Translates to @new_x = self.x + 320

Is there a way I can do that? Basically, I need to modify a property's operator methods, like @new_x += ? and @new_y -= ? and stuff like that. In other words, I'm trying to get rid of the dependancy on the x_to(), y_to(), fade_opacity() type methods, since all they do is set instances (and share the same @delay instance for move speed), and just redefine their operators to mimic my example.

 

[Dargor]

I think you can do that by adding a method to your window and in your case, the method name would be new_x=.

def new_x=(n)
  # your code here
end

 

[Kain Nobel]

Well, I'm trying to do it strictly for +/- but its not working, it just gives a syntax error pointing at the definition (although = works fine, but thats not what I'm needing.)

 

[Dargor]

Have you tried

def new_x+=(n)
  # your code here
end
def new_x-=(n)
  # your code here
end

I've never tried it before, except for the =, so I'm not suree if these 2 methods will work.
But the = method will also take + and - into consideration.

 

[Zeriab]

object += value # Is the same as
object = object + value

You just have to define +(value) methods for the class the object is an instance of.

Here's an code example which hopefully can help you understand how to do it:

class Foo
  def initialize
    @bar = 0
  end
  
  def +(val)
    @bar += val
    return self
  end
  
  def -(val)
    @bar -= val
    return self
  end
  
  def inspect
    "Foo = " + @bar.to_s
  end
end

class Bar
  attr_accessor :foo
  def initialize
     @foo = Foo.new
  end
end


a = Foo.new
p a
a += 4
p a
a -= 24
p a

b = Bar.new
p b
b.foo += 2
p b
b.foo -= 4
p b

*hugs*
- Zeriab

 

[Dargor]

I guess it works the same as redefining [] like in Game_Actors. That's cool, might be useful to me sooner or later.

 

[Zeriab]

The difference between foo 

 

[e]

Not that you couldn't write a method named "+=" though, just to confuse people like Zeriab :grin:

 

[Zeriab]

Yes indeed it would like those overloaded methods in C# where the number of arguments remains the same :x

 

[Kain Nobel]

How exactly do I tell which instance variables are being += or -= from? Theres only 5 or so instances that I need this behavior for, because they're special to the Window Movable script, but they're all Window-class properties, so I can't be doing self.width + 320 because that would be self.width = self.width + 320 and thats not the kind of behavior I want all the variables to do, just certain ones.

The 'movable' instances on the other hand will follow their own rules for the += / -= command though, because self.new_x += 5 would mean that it would slide over 5 pixels from its current spot, or self.new_o -= 160 means that opacity would fade from current to minus 160. I don't know how to do it only for @new_x, @new_y, @new_o, @new_co and @new_z.

 

[e]

You can specify singleton methods on objects like this :

def myObject.method_name(arg1, arg2, ..., argN)
  puts "I am SINGLETOR!"
end

That method would be available only the object myObject.

In your case, it could be:

def @windowA.+(aNumber)
  self.width += aNumber
end

Or whatever. I didn't read the whole topic. Just Google Ruby Singleton Methods for more.