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Ruby Build an Address Book in Ruby Class Design Contact Class: Part 1

Posted by Alexander Mooney
Alexander Mooney
7,321 Points

Why do we use attr_writer instead of attr_accessor?

Wouldn't it be simpler to just use attr_accessor instead of writing out a reader for each attribute? Am I misunderstanding how accessor, reader, and writer work?

class Contact
  attr_writer :first_name, :middle_name, :last_name

  def first_name
    @first_name
  end

  def middle_name
    @middle_name
  end

  def last_name
    @last_name
  end

  def full_name
    full_name = first_name
    if !@middle_name.nil?
      full_name += " "
      full_name += middle_name
    end
    full_name += ' '
    full_name += last_name
    full_name
  end
end

2 Answers

Bill Rogers
Bill Rogers
12,944 Points

Forgive me if I'm wrong, but I'm pretty sure you are correct in that, in this context, accessor would give you:

def first_name=(value)
  @first_name = value
end

and 

def first_name
  @user
end

Whereas writer gives you the first method above, and then you write out the second by hand. Could be for practice?

Alexander Mooney
Alexander Mooney
7,321 Points

I thought that may be it, but wanted to confirm rather than just assuming and being wrong. Thanks for the answer!

Tiago Ferrão
Tiago Ferrão
10,873 Points
Tiago Ferrão
Tiago Ferrão
10,873 Points

indeed! this is how I wrote the whole class in less than 10 lines and it seems to work with the same behaviour:

class User attr_accessor :first_name, :middle_name, :last_name

def full_name if middle_name.nil? full_name = first_name + " " + last_name else full_name = first_name + " " + middle_name + " " + last_name end end end

Alphonse Cuccurullo
Alphonse Cuccurullo
2,513 Points
Alphonse Cuccurullo
Alphonse Cuccurullo
2,513 Points

Whats with the += stuff in this syntax? Couldnt you just have did the + symbol? also why did you input end after the @middle name? Im having problems understanding the order of all this syntax someone help please?

Rodrigo Castro
Rodrigo Castro
15,652 Points
Rodrigo Castro
Rodrigo Castro
15,652 Points

Hi Alphonse,

Writing 'full_name += last_name' is the same as writing 'full_name = full_name + last_name', however the former is shorter. The 'end' after the @middle_name is used to close the method body which will return the @middle_name variable.

hope it helps.