Atribute and @variables. what's the difference?

[Valdred]

Yeah, what is the difference between attributes and variables?
I don't get it.

[Blizzard]

Attributes are usually a term from the object oriented paradigm. An object has an attribute, i.e. My attribute would be that I have blue eyes. A variable is a concept from programming (it's also one from mathematics, but that's irrelevant here) and it is used to describe or "contain" a value that represents an attribute.

In ruby instance variables are also called attributes.

[Fantasist]

As for a more limited clarification, what you define as "attr_reader", "attr_accessor", "attr_writer" are simply instance variables (variables starting with a single "@") with methods to modify them from outside the object:

attr_reader :eye_color

#=== That equals ===

def eye_color
   return @eye_color
end

attr_writer :eye_color

#=== That equals ===

def eye_color=(value)
   @eye_color = value
end

attr_accessor :eye_color

#=== That equals ===

def eye_color
   return @eye_color
end

def eye_color=(value)
   @eye_color = value
end

[Zeriab]

I'll assume you mean the difference between instance variables (@var) and attribute constructors (attr_XXXX) in rgss.
In that case the attribute constructors are shortcuts for creating getters and settings of instance variables. In other words. shortcuts for for allowing instance variables to be seen and/or changed from outside the object.
Instance variables keep instance relevant data. I.e. to the specific object.

[Valdred]

Thanks a lot guys. do @abc equal :abc? or did I misunderstand.

But one more thing.

What is the difference between attr_accessor and attr_reader?

[Blizzard]

@abc is the value of the variable while :abc is the variable object itself that contains the value.

attr_reader allows only read-only access of the variable object's value while attr_accessor allows writing (aka changing) the value as well. There's also attr_writer which allows only writing and no reading.

[Valdred]

I see, thank you very much for your help. *levels up*

[Zeriab]

:abc is a symbol.
You can consider it like an immutable string where equal strings refer to the same object.

a = :abc
b = :abc
p a == b  # => true
p a.id == b.id # => true

[Valdred]

ah, I see. Thank you.

*levels up & hugs*