Scientist::Experiment.new creates Scientist::Default instance even when it should have been overridden #92

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1. mermop

   changed the title [-]`Scientist::Experiment.new` creates `Scientist::Default` instance even when it should have been overridden[/-] [+]Scientist::Experiment.new creates Scientist::Default instance even when it should have been overridden[/+] on Oct 19, 2018
2. mermop commented on Oct 19, 2018

   

   mermop

   on Oct 19, 2018

   Author

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   For the moment I've moved this block of code into an initializer:

   module Scientist::Experiment
     def self.new(name)
       LdapExperiment.new(name: name)
     end
   end

   Which seems to work, so maybe it's just worth noting that strategy in the README

   👍React with 👍1Reacted by Shan Gardezi
3. benterprise commented on Jan 15, 2019

   

   benterprise

   on Jan 15, 2019

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   I also ran into this problem and got around it by using the initializer above

   👍React with 👍1Reacted by Merrin Macleod
4. Linuus commented on Sep 5, 2019

   

   Linuus

   on Sep 5, 2019

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   Super late response but maybe it helps someone else :)

   Rails lazy loads classes in development. So, your experiment file has not been loaded yet and thus, the default experiment has not been overridden. That's why it works after you instantiate your experiment once which forces Rails to load the file.
5. myhandisout commented on Jun 9, 2021

   

   myhandisout

   on Jun 9, 2021

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   Hi friends! Thank you for your great work with this gem ✨

   I am having a problem in Rails apps where Scientist::Experiment defaults to the original Default object until the custom one is called - leading to some head-scratching about why the try block is not running even when enabled? is set to true.

   I'm unsure whether this is a problem with the Rails load order because of how I've arranged my files, whether the examples in the README could be a little better, or whether there's genuinely a bug here.

   $ bundle exec rails console
   Loading development environment (Rails 5.1.6)
   irb(main):001:0> Scientist::Experiment.new "something"
   => #<Scientist::Default:0x00007fd667bbcd40 @name="something">
   irb(main):002:0> LdapExperiment.new(name: "something")
   => #<LdapExperiment:0x00007fd667b6ee10 @name="something">
   irb(main):003:0> Scientist::Experiment.new "something"
   => #<LdapExperiment:0x00007fd667b34968 @name="something">
   

   I've followed the instructions in the README, which are delightful and comprehensive.

   # app/experiments/ldap_experiment.rb
   require "scientist/experiment"
   
   class LdapExperiment
     include Scientist::Experiment
   
     attr_accessor :name
   
     def initialize(name:)
       @name = name
     end
   
     def enabled?
       # ...
     end
   
     def publish(result)
       # ...
     end
   end
   
   module Scientist::Experiment
     def self.new(name)
       LdapExperiment.new(name: name)
     end
   end

   # app/models/whatever.rb
   class Whatever
     include Scientist
     def do_something
       science "role lookup" do |e|
         e.use { do_one_thing }
         e.try { do_some_other_thing }
       end
     end
   end

   This is occurring in Rails 3.2.x and Rails 5.1.x applications, with version 1.2.0 of the gem.
6. benoittgt commented on Feb 28, 2023

   

   benoittgt

   on Feb 28, 2023

   Last edited by benoittgt

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   I did that, and it's ugly

   class User < ApplicationRecord
   
     # Force loading of class otherwise `scientist` load the default
     # experiment class which is not what we want
     DefaultExperiment # our custom class that is enabled withe proper result
     extend Scientist # because it is on class method
   
   end