Why don't these writable atributes work?

ruby-talk
1

Both of these code examples for making class properties don't work
although they are pretty much straight out of the book "Programming
Ruby". What I am doing wrong here?

error is: undefined method `firstName' for #<User:0xb7f76b24
@firstName="Newton"> (NoMethodError)

···

----------------------
class User

  attr_writer :firstName

  def initialize(firstName)
    @firstName = firstName
  end
end

user = User.new('Hal')
user.firstName = 'Newton'
print user.firstName
--------------------------------

class User

  def firstName=(newFirstName)
    @firstName = newFirstName
  end

  def initialize(firstName)
    @firstName = firstName
  end
end

user = User.new('Hal')
user.firstName = 'Newton'
print user.firstName

--------------------------------

Thanks,

Edward Tanguay
All my projects: http://www.tanguay.info

2

Edward wrote:

Both of these code examples for making class properties don't work
although they are pretty much straight out of the book "Programming
Ruby". What I am doing wrong here?

error is: undefined method `firstName' for #<User:0xb7f76b24
@firstName="Newton"> (NoMethodError)
----------------------

you didn't create an attribute reader:

attr_accessor :firstName - creates both reader and writer

attr_writer :firstName - creates a writer

attr_reader :firstName - creates a reader (the one that you need)

You can also create a reader by hand:

def firstName
  @firstName
end

lopex

3

'attr_writer :firstName' only creates the 'firstName=' method just
like 'attr_reader :firstName' will only create the 'firstName' method.
What you need is 'attr_accessor :firstName' which creates both.

Farrel

···

On 17/09/06, Edward <edward@tanguay.info> wrote:

Both of these code examples for making class properties don't work
although they are pretty much straight out of the book "Programming
Ruby". What I am doing wrong here?

error is: undefined method `firstName' for #<User:0xb7f76b24
@firstName="Newton"> (NoMethodError)
----------------------
class User

        attr_writer :firstName

        def initialize(firstName)
                @firstName = firstName
        end
end

user = User.new('Hal')
user.firstName = 'Newton'
print user.firstName
--------------------------------

class User

        def firstName=(newFirstName)
                @firstName = newFirstName
        end

        def initialize(firstName)
                @firstName = firstName
        end
end

user = User.new('Hal')
user.firstName = 'Newton'
print user.firstName

--------------------------------

Thanks,

Edward Tanguay
All my projects: http://www.tanguay.info

4

Edward wrote:

Both of these code examples for making class properties don't work
although they are pretty much straight out of the book "Programming
Ruby". What I am doing wrong here?

error is: undefined method `firstName' for #<User:0xb7f76b24
@firstName="Newton"> (NoMethodError)
----------------------
class User

  attr_writer :firstName

Just an additional note: the usual conventions for method and variable identifiers in Ruby is to separate words by underscore and use camel case only for class and module names. So that would rather be

class User
   attr_accessor :first_name
end

Kind regards

  robert