Ruby Instance Variable Syntax

Question

I'm finishing The Well Grounded Rubyist and I've noticed some instance variable calls that I don't quite understand. Straight from TWGR (Section 15.2.2):

class Person
  attr_reader :name
  def name=(name)
    @name = name
    normalize_name
  end

  private
  def normalize_name
    name.gsub!(/[^-a-z'.\s]/i, "")
  end
end

Is the name variable in the normalize_name method an implicit instance variable? Would @name.gsub!(/[^-a-z'.\s]/i, "") have worked just as well? Is there some convention I should be aware of?

coreyward · Accepted Answer · 2012-03-17 03:49:08Z

2

What's happening in normalize_name is that name resolves to the method self.name, which is defined by the attr_reader class macro at the top of the class. If you were to use attr_accessor instead, the name= method would be defined as well (but it wouldn't include the call to normalize_name.

These getter and setter methods automatically access instance variables. The name method defined by attr_accessible :name looks like this, essentially:

def name
  @name
end

answered Mar 17, 2012 at 3:49

coreyward

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2 Comments

rringler Over a year ago

Would referencing the @name variable directly instead of the name method have worked? Is there an advantage to using the name method?

coreyward Over a year ago

Yup. They do the same basic thing, but it's safer to use the getter — what if later down the line you decide to modify the data on read instead of on write?

Jörg W Mittag · Accepted Answer · 2012-03-17 09:55:08Z

0

Is the name variable in the normalize_name method an implicit instance variable?

No, it's not an instance variable. Instance variables start with an @ sigil, this doesn't, ergo, it cannot possibly be an instance variable. In fact, it's not a variable at all, it's a message send.

answered Mar 17, 2012 at 9:55

Jörg W Mittag

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