Confused with object initialization/instance variables

Question

I use the following class definition

 class Workflow
    # class << self; attr_acessor :id, :name, :url  end
    # Please ignore the troubleshooting attemp above it didn't help, I got the ObjectNil

    def self.initialize ( id, name, url )
      @id = id
      @name = name
      @url = url
    end

    # @return [Object]
    def  self.list
      ret = Array.new
      wf = Hash.new
      vco = Vco.new
      vco.getAll.each do |link|
        link['attributes'].each do |attr|
          wf[ attr['name'] ] = attr[ 'value' ]
        end
        ret.push( self.new( wf[ 'id' ], wf[ 'name' ], wf[ 'itemHref' ]  ) )
      end
      return   ret
    end

used as:

  <% @workflows.each do |wf| %>
      <tr>
        <td><%= wf.id %></td>
        <td><%= wf.name %></td>
        <td><%= wf.url %></td>
      </tr>
  <% end %>

Thus the method Workflow.list should return an array of workflows. However, it doesn't do so as expected. When I use

        ret.push( self.new( wf[ 'id' ], wf[ 'name' ], wf[ 'itemHref' ]  ) )

I'm getting the "wrong number of arguments(3 for 0)" error. But when I use instead

       ret.push( self.initialize( wf[ 'id' ], wf[ 'name' ], wf[ 'itemHref' ]  ) )

the method list returns a list of url strings (it is the last assignment in the method, and should be that) What am I doing wrong?

@sawa Sorry, "initialiSe" was a typo made during the post preparation. In real code there was initialiZe. — Vsevolod Semouchin
– Vsevolod Semouchin, Commented May 21, 2013 at 11:03

Arup Rakshit · Accepted Answer · 2013-05-21 10:42:41Z

1

to remove that error on self.new call, change the def self.initialize ( id, name, url ) to def initialize ( id, name, url ). self.new tries to create a Workflow instance,by calling default initialize method, which don't take any arguments,but you are providing it arguments,which in turn throws error.

edited May 21, 2013 at 10:42

answered May 21, 2013 at 10:35

Arup Rakshit

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10 Comments

Vsevolod Semouchin Over a year ago

Just tested it "def initialize ( id, name, url )" and "ret.push( self.new( wf[ 'id' ], wf[ 'name' ], wf[ 'itemHref' ] ) )" now getting error "undefined method `id' for #<Workflow:0x4006e90>"

Arup Rakshit Over a year ago

@Vsevolod use as wf[@id]

Vsevolod Semouchin Over a year ago

:( "undefined method `[]' for #<Workflow:0x4573a58> -- but in my understanding instance variables in Ruby are the same as objct properties in other languages, or I#m speaking nonsense?

Arup Rakshit Over a year ago

ue attr_acessor :id, :name, :url in the class.

Anand Shah Over a year ago

@Priti :

self.new tries to create a Workflow instance,by calling default initialize method, which don't take any arguments,but you are providing it arguments,which in turn throws error.

- self.new will call the initialize method which is accepting 3 arguments.

|

Anand Shah · Accepted Answer · 2013-05-21 10:36:52Z

0

First you've got def self.initialize which should be changed to def initialize since its a constructor. Constructor is a method that gets called when you do Class.new since you've defined the constructor as a class method you are getting the error.

Second the constructor is called initialize and you are making a call to initialise (typo?) if not fix that part as well.

answered May 21, 2013 at 10:36

Anand Shah

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1 Comment

Vsevolod Semouchin Over a year ago

Sorry, "initialiSe" was a typo made during the post preparation. In real code there was initialiZe

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