Try create my own Struct via Ruby

Question

I can't inherit the Struct. I must implement class which act like Struct. Is there a way improve my code for use "ClassName" and functional like Struct ? And write k=Dave.new("Rachel" , "Greene") ???

class MyStruct
  def self.new(*attributes)
    puts "ppp"
    dynamic_name = "ClassName"
    Kernel.const_set(dynamic_name,Class.new()  do
      attributes.each do |action|
        self.send(:define_method, action) {
          puts "call #{action}" 
        }
      end  
    end
    )
  end
end

# class ClassName
  # def new *args 
    # puts "iii"
  # end
# end



Dave = MyStruct.new(:name, :surname)

k=Dave.new()     # k=Dave.new("Rachel" , "Greene")
k.surname
k.name

Uri Agassi · Accepted Answer · 2014-06-01 13:22:47Z

5

Here is a version of your code which works:

class MyStruct
  def self.new(*attributes)
    Class.new do
      self.send(:attr_accessor, *attributes)
      self.send(:define_method, :initialize) do |*values|
        values.each_with_index { |val, i| self.send("#{attributes[i]}=", val) }
      end  
    end
  end
end

Dave = MyStruct.new(:name, :surname)
k = Dave.new('Rachel', 'Green')
# => #<Dave:0x00000001af2b10 @name="Rachel", @surname="Green"> 
k.name
# => "Rachel"
k.surname
# => "Green"

You don't need to const_set inside the method - Dave = is enough
I'm creating here an attr_accessor for each of the attributes, so you are getting a getter and a setter for each
In the initialize method I'm sending each value to its corresponding setter, to set all values. If there are less values than anticipated, the last attributes will not be set, if there are more - an exception will be thrown (undefined method '=')

answered Jun 1, 2014 at 13:22

Uri Agassi

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3 Comments

user3500854 Over a year ago

WoW ! Thank you so much. Good luck for you!

user3500854 Over a year ago

Sorry If I bother you. Why I can't write k["name"] ?

Cary Swoveland Over a year ago

A small thing: self.send can be written send.

bodacious · Accepted Answer · 2014-06-01 13:14:36Z

3

Have you looked at the Struct class in Ruby?

http://www.ruby-doc.org/core-2.1.2/Struct.html

class MyStruct < Struct.new(:first_name, :last_name)

end

MyClassObj = MyStruct.new("Gavin", "Morrice")

Also, you shouldn't ever overwrite self.new, define initialize instead

answered Jun 1, 2014 at 13:14

bodacious

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2 Comments

user3500854 Over a year ago

Sorry , but for my task I can't inherit the Struct. I must implement class which act like Struct.

Cary Swoveland Over a year ago

Isn't "shouldn't ever" a bit extreme? Suppose, for example, you wanted to compile a list of class instances in a class instance variable? I would view that as a job for the class, so would put it in new, rather than have instances invoke self.class.instance_variable_get... and ...set in initialize.

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