CODEWITHSUNDEEP
rubyclasscoding-styleinstance-variables
user4252294
user4252294

Reputation:

Setting not initialized instance variable

Is it elegant to use instance variables in a class which are not initialized and setting them using other methods? Or maybe there is a better way to do that?

class Klass
  def initialize(a)
    @a = a
  end

  def set_b(b)
    @b = b
  end
end

Upvotes: 2

Views: 116

Answers (2)

mhutter
mhutter

Reputation: 2916

In contrast to other languages, If you do not initialize an instance variable it will always be nil (whereas in certain other languages you could get something undefined).

As long as other methods of Klass do not depend on the instance variable actually having a value, this should be ok.

As for getters and setters, there are attr_accessor, attr_reader and attr_writer (see the docs).

class Klass
  attr_accessor :b
  # there's also attr_reader and attr_writer

  def initialize(a)
    @a = a
  end
end

k = Klass.new :foo
k.b = :bar

k.b
#=> :bar

k.a
#=> undefined method `a' for #<Klass:0x007f842a17c0e0 @a=:foo, @b=:bar> (NoMethodError)

Upvotes: 1

J&#233;r&#244;me
J&#233;r&#244;me

Reputation: 8066

The way you are doing it works but Ruby defined attr_accessor, attr_reader and attr_writer for that purpose.

attr_reader: create method to read 'a'

attr_writer: create method to write 'a'

attr_accessor: create methods to read and write 'a'

I think the best way to do that is to use attr_accessor:a

class Klass
  attr_accessor:a
  def initialize(a)
    @a = a
  end
end

Then you can do:

k = Klass.new "foo" #example 
k.a = "bar"

Upvotes: 0

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