How to get private variables of instance object without calling method

Question

Is it possible to call a specific method (or getting instance variables) without instance method from instance object in Ruby?

class Foo
  def initialize(arg)
    @bar = arg
  end
end

f = Foo.new('test')
p f #=> "test" (in this case, get @bar variable without instance method)

For instance, if Example class is defined,

ex = Example.new
ex #=> #<Example:0x00000000000000>

I want to do, like this.

ex = Example.new('hello')
ex #=> "hello"

unclear what you're asking. What you want can be achieved my overriding the to_s method — Andrey Deineko
– Andrey Deineko, Commented Nov 17, 2016 at 14:26
you can use attr_reader :bar to get ruby to write the getter for you? — Joseph Weissman
– Joseph Weissman, Commented Nov 17, 2016 at 14:27
I want to get a value without instance method (including attr). For example, instance of String returns its value. When I call its initialize method s = String.new('foo') , I can access its value without instance method s #=> 'foo' . — Yohsuke Inoda
– Yohsuke Inoda, Commented Nov 17, 2016 at 14:30
Re-read your question: "how to call a method without a method". It doesn't make sense! — Sergio Tulentsev
– Sergio Tulentsev, Commented Nov 17, 2016 at 14:30
You're confusing two things together: string representation of an object and its actual value. These are very different. — Sergio Tulentsev
– Sergio Tulentsev, Commented Nov 17, 2016 at 14:32

Bartłomiej Gładys · Accepted Answer · 2016-11-17 14:39:31Z

1

You can use inspect for p and to_s for puts

class Foo
  def initialize(arg)
    @bar = arg
  end
  def inspect
    @bar
  end
  def to_s
    @bar
  end
end

f = Foo.new('test')
puts f #=> "test"
p f #=> "test"

edited Nov 17, 2016 at 14:39

answered Nov 17, 2016 at 14:34

Bartłomiej Gładys

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2 Comments

Sergio Tulentsev Over a year ago

For p you want .inspect

steenslag Over a year ago

@YohsukeInoda no you can't use it everywhere: p f.capitalize results in a NoMethodError.

steenslag · Accepted Answer · 2016-11-17 16:43:44Z

0

The return value of the initialize method is ignored; initialize always returns self, in this case an instance of Foo. Defining a to_s method just defines a string representation of the Foo instance.

f = Foo.new('test')

p f #=> "test"
p f.class #=> Foo

So after ex = Example.new('hello'), ex will always be a Example instance. It can not be a string or whatever.

edited Nov 17, 2016 at 16:43

answered Nov 17, 2016 at 16:23

steenslag

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