Question

Can you tell me why this isn’t working?

The code below outputs student1 & student2 properly, but I cannot get the class method to work on student3.

All I am trying to do is assign a class method .create_with_species , with the species attribute = to “Human”.

However, when I run the program, I get an error that “local variable or method sex is undefined”. I’m a newbie and I can’t figure out what I’ve done wrong!

It was my understanding that since I had identified “sex” in the Initialize method I should be able to use it within a class method such as create_with_species. I tried explicitly defining sex in the class method, as student.sex = sex, but still got the same error.

class Students

  attr_accessor :sex, :age, :species

  def self.create_with_species(species)
    student = Students.new(sex,age)
    student.species = species
    return student
  end

  def initialize(sex, age)
    @sex = sex
    @age = age
    puts "----A new student has been added----"
  end

end

student1 = Students.new("Male", "21")
puts student1.sex
puts student1.age
puts

student2 = Students.new("Female", "19")
puts student2.sex
puts student2.age

student3 = Students.create_with_species("human")

Answer 1

sex and age are not defined. Do you mean to use a class variable? Using @age or @sex will result in nils, as no class attributes are set and the instance is not yet created, hence no instance variables set either. You don’t need to state Students.new in create_with_species. new will suffice because you are scoped in Students. I think you would be better off passing a hash object to initialize, and just set the species variable there. It will be nil if not assigned explicitly, or you can have a default value.

Try this:

class Students

  attr_accessor :sex, :age, :species

  def initialize(options)
    @sex = options[:sex]
    @age = options[:age]
    @species = options[:species]
    puts "----A new student has been added----"
  end

end

student1 = Students.new(:sex => "Male", :age => "21")
puts student1.sex
puts student1.age
puts student1.species
puts

student2 = Students.new(:sex => "Female", :age => "19")
puts student2.sex
puts student2.age

student3 = Students.new(
    :sex => "Hermi", :age => "2", :species => "alien"
)