CODEWITHSUNDEEP
ruby
PhillieJs
PhillieJs

Reputation: 21

Why do I get an argument error?

This is copied from Eloquent Ruby book:

class Document

    def words 
        @content.split 
    end 
    def word_count 
        word.size

    end 
end 


doc = Document.new("Ethics", "Spionza", "By that which is...")

doc.word_count

I get this error:

`initialize': wrong number of arguments (3 for 0) (ArgumentError)

I do not understand why. What's wrong with this example?

Upvotes: 1

Views: 677

Answers (3)

SteveTurczyn
SteveTurczyn

Reputation: 36860

As has been mentioned, you need to define an initialize method.

In Ruby, the initialize method is an instance method called automatically when you use the .new class method, and the class method arguments are passed to the instance method.

You have three arguments: "Ethics", "Spionza" and ""By that which is..."

So because there's no #initialize method, the Ruby default is used, which expects no arguments but you're passing three.

(and you misspelled "Spinoza" :) )

In your use case it should probably look like this.

class Document

  def initialize(category, author, content)
    @category = category
    @author = author
    @content = content
  end

  def words 
    @content.split 
  end 

  def word_count 
    words.size
  end
end



doc = Document.new("Ethics", "Spionza", "By that which is...")

doc.word_count

Upvotes: 2

orde
orde

Reputation: 5273

As @fiskeben points out, you need to define an initialize method and specify the appropriate arguments. The example below accepts 2 arguments, which are set as instance variables.

Note that the method body of the word_count method has been changed to access the @content instance variable (since it's not clear where the word variable in word.size is defined).

class Document

  def initialize(name, content)
    @name = name
    @content = content
  end

  def words 
    @content.split 
  end 

  def word_count 
    @content.size
  end 
end 


doc = Document.new("Book Name", "Book Content")

puts doc.word_count

Upvotes: 0

fiskeben
fiskeben

Reputation: 3467

You haven't specified a constructor (def initialize) and the default constructor only takes zero arguments.

Add the initialize method to your class.

Upvotes: 1

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