CODEWITHSUNDEEP
ruby
dislikesAppleCores
dislikesAppleCores

Reputation: 320

What is 'self' inside initialize()?

say I have this:

class Post
  def initialize()
    vote_total = 0
  end
end

Obviously, this won't set an instance variable, and to do so, inside initialize this needs to be written

self.vote_total = 0

My question is...what is self inside the initialize method?

irb(main):022:0> class Post
irb(main):023:1> puts self
irb(main):024:1> def initialize()
irb(main):025:2> puts self
irb(main):026:2> vote_total = 0
irb(main):027:2> puts self
irb(main):028:2> end
irb(main):029:1> end
Post
=> nil
irb(main):030:0> post = Post.new
#<Post:0x007f9448d76f98>
#<Post:0x007f9448d76f98>
=> #<Post:0x007f9448d76f98>

I understand the difference but functional similarity between

@instance_variables

obj.method_instance_variables

but I don't understand whats going on in that vote_total line. what is self there, and what is getting vote_total defined?

Upvotes: 1

Views: 3649

Answers (1)

BroiSatse
BroiSatse

Reputation: 44725

initialize is an instance method so self refers to new instance of the class. When you execute self outside of any method (in class body), self refers to the class itself).

OTHER NOTES:

Neither of:

vote_total = 0
self.vote_total = 0

set an instance variable 'per se'. First call creates local variable vote_total, second call executes method vote_total=. If your class has attr_accessor or attr_reader on top, then this method is defined as 

def vote_total=(value)
  @vote_total = value
end

which is setting the variable. If you have none of those and you don't define it any other way (number of ways is extremely huge), then self.vote_total = :foo will raise undefined method 'vote_total=' exception.

Upvotes: 3

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