CODEWITHSUNDEEP
rubyclassinstance
Sean Bernardino
Sean Bernardino

Reputation: 195

How do I create an instance of a class from a loop in Ruby?

I'm trying to initialize an instance of a class from within a loop and am not sure how I would name the object so that it has a new name with each iteration so I don't have five objects/instances all called 'my_animal'?

my_array = ["Fluffy", "Lala", "Jo", "Cersei", "Berlin"]
my_array.each do |e|
    my_animal = Animal.new(e)
end


class Animal
attr_accessor :name
    def initialize (name)
        @name = name
    end


end

Upvotes: 1

Views: 1742

Answers (4)

Cary Swoveland
Cary Swoveland

Reputation: 110665

You could do this:

my_array = ["Fluffy", "Lala", "Jo", "Cersei", "Berlin", "Jo"]
arr = my_array.each_with_index.with_object([]) do |(e,i),a|
    a << Animal.send(:new, "#{e}#{i}")        
end
  #=> [#<Animal:0x007fe3e4087b20 @name="Fluffy0">,
  #    #<Animal:0x007fe3e4087a80 @name="Lala1">,
  #    #<Animal:0x007fe3e40879e0 @name="Jo2">,
  #    #<Animal:0x007fe3e4087940 @name="Cersei3">,
  #    #<Animal:0x007fe3e4087878 @name="Berlin4">,
  #    #<Animal:0x007fe3e31d5618 @name="Jo5">] 

arr.map(&:name)
  #=> ["Fluffy0", "Lala1", "Jo2", "Cersei3", "Berlin4", "Jo5"]

Alternatively, the following way conveys additional information:

my_array = ["Fluffy", "Lala", "Jo", "Cersei", "Lala", "Jo", "Berlin", "Jo"]
arr = my_array.each_with_object([]) do |s,a|
  instance = a.reverse.find { |i| i.name =~ /^#{s}/ }
  if instance
    old_name = instance.name
     prefix, nbr = old_name.split(/(\d+)/)
    new_name = "#{prefix}#{((nbr.to_i)+1).to_s}"
  else 
    new_name = "#{s}0"
  end        
  a << Animal.send(:new, new_name)        
end
  #=> [#<Animal:0x007fe3e402e458 @name="Fluffy0">,
  #    #<Animal:0x007fe3e402e1b0 @name="Lala0">,
  #    #<Animal:0x007fe3e402dc38 @name="Jo0">,
  #    #<Animal:0x007fe3e402d120 @name="Cersei0">,
  #    #<Animal:0x007fe3e402c540 @name="Lala1">,
  #    #<Animal:0x007fe3e4097d68 @name="Jo1">,
  #    #<Animal:0x007fe3e4096d00 @name="Berlin0">,
  #    #<Animal:0x007fe3e4096698 @name="Jo2">] 
arr.map(&:name)
  #=> ["Fluffy0", "Lala0", "Jo0", "Cersei0", "Lala1", "Jo1", "Berlin0", "Jo2"]

Upvotes: 2

David Lilue
David Lilue

Reputation: 631

What happend on your code, its that every instance you create on my_animal = Animal.new(e) its lost. You have to keep trace of all of them on some structure. Like a dictionary (hash) or array.

This could be helpful:

class Animal
    attr_accessor :name

    def initialize (name)
        @name = name
    end
end

my_array = ["Fluffy", "Lala", "Jo", "Cersei", "Berlin"]

my_instances = {}

my_array.each do |e|
    my_animal = Animal.new(e)

    my_instances[e] = my_animal
end

Now you have a name (string) of your array with an object. It will be something like:

my_instance = { "Fluffy" => #<Animal:0x0000000280d638 @name="Fluffy">,
                "Lala"   => #<Animal:0x0000000280d5e8 @name="Lala">,
                "Jo"     => #<Animal:0x0000000280d598 @name="Jo">,
                "Cersei" => #<Animal:0x0000000280d548 @name="Cersei">,
                "Berlin" => #<Animal:0x0000000280d4f8 @name="Berlin">
              }

Upvotes: 1

Stephan Rodemeier
Stephan Rodemeier

Reputation: 717

You can try to put them in a Hash, then you can access them like my_animals["Lala"].

class Animal
  attr_accessor :name
  def initialize (name)
    @name = name
  end
end

my_array = ["Fluffy", "Lala", "Jo", "Cersei", "Berlin"]
my_animals = Hash.new

my_array.each do |e|
  my_animals[e] = Animal.new(e)
end

Upvotes: 1

Etain LaFae
Etain LaFae

Reputation: 11

Push all new objects into an array rather than a static variable and then you can access them numerically.

Upvotes: 1

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