CODEWITHSUNDEEP
ruby
the_prole
the_prole

Reputation: 8985

Do Ruby instance variables have access modifiers?

So what I learned is that when I call a variable on an object e.g.

my_object.variable

A method called variable is returning the value of variable

def variable
   @variable
end

In Java, there are access modifiers. How can Ruby make use of access modifiers if getter methods are named after their variables?

Upvotes: 2

Views: 277

Answers (2)

Ray Toal
Ray Toal

Reputation: 88418

First, there is a bit of terminology to clean up in the question before answering it.

One is that you never "call" variables. The Ruby expression

my_object.variable

is a method call. There is no such thing as a variable call. You call methods, not variables. Even if the method is named variable. :)

The second is if you did define the method like this

def variable
   @variable
end

either directly or by saying

attr_reader :variable

Then you have a method named variable and a variable named @variable.

Now to answer the question.

Ruby places access modifiers public, protected, and private on methods only, and not on variables. Access controls on variables don't really make sense, because they only be referenced within an object’s methods, and never with a prefix! In other words, you can never write this:

obj.@var

That's just a syntax error. You can write

obj.var

where var is the name of a method. And the access controls apply to that method only.

The fact that you may be making variables and methods with the same name (except for the @) actually doesn't matter. Only methods have access controls.

Hope that helps clear up some understandable confusion!

Upvotes: 7

spickermann
spickermann

Reputation: 106972

There are several ways to make a method private in Ruby.

Use private to make all later methods private:

class Foo
  def public_method
  end

private

  def private_method
  end
end

Or make a method private after you defined it:

class Foo
  def public_method
  end

  private :public_method # public_method is now private
end

Or - since the method definition returns a symbol too - this also works:

class Foo
  private def method_name
  end
end

Upvotes: 3

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