How to Require Activerecord in Irb

How to require ActiveRecord In IRB

Try require('active_record')

If you take a look at the gem Github repo the actual file name is active_record.rb so the above code should work.

https://github.com/rails/rails/tree/master/activerecord/lib

Requiring ActiveRecord on IRB - Ruby (NO Rails)

Two things to change here:

1. Always put quotes around the path you're requiring. The reason Ruby is saying "undefined local variable or method" is that it's trying to interpret config as a variable name. Put the name in quotes and it won't.
2. Use require_relative when loading files that are part of your application. require only looks in the default Ruby load paths.

Try this:

    require_relative 'config/application.rb'

Do I need a model to insert through IRB?

yes error is due to not having a Department class or model. You can just create a department.rb and inherited from active record in your app/models directory with your favourite editor. for example with vim you can do

vim app/models/department.rb

edit the above file to have following

class Department < ActiveRecord::Base
end

and then reload the irb session with reload!

What all things can you access when you require a gem?

Thats up to the gem developer. To see how your Name- and Objectspace changed there should be many clever ways.

I answer shortly how to find out which new Module (-Constants) there are:

  initial_modules = Module.constants
  # -> [:Object, :Module, :Class, :BasicObject, :Kernel, :NilClass, ...]

  require 'rails'

  Module.constants - initial_modules # all NEW constants
  # -> [:Pathname, :OpenSSL, :Digest, :SecureRandom, :Concurrent, :I18n, :CGI, :ActiveSupport, :Set, :SortedSet, :Timeout, :TimeoutError, :Logger, :LoggerSilence, :DateAndTime, :Psych, :StringScanner, :ScanError, :Date, :DateTime, :YAML, :Base64, :TSort, :Rails, :BigDecimal, :BigMath, :TZInfo, :ThreadSafe, :Threadsafe, :SynchronizedDelegator, :JSON, :OpenStruct, :Singleton, :Mutex_m, :ActionPack, :Rack, :ActionDispatch, :Mime]

As you see, this also comes with a lot of new stuff that is required (but not provided) by Rails, like Date, OpenSSL, etc.pp.
Actually, requirements can happen at runtime, too, such that this lists grows as you use the code.
Hope that helps a bit.

forcing an unmaintained ActiveRecord adapter to Rails version 6

@rmlockerd and @ruby_object were both correct in helping to debug, but at the end of the day I'd just written the section of code in a way that didn't work.

debugging was key

While doing a practice db migration in rails using irb, receiving error message NameError:uninitialized constant ActiveRecord

You need to require 'active_record'. I agree that you may run into other issues trying to migrate by hand.

uninitialized constant ActiveRecord

start your irb session with

rails console

and not:

irb

rails console would load your rails environment and your model for you, so you can do things like:

User.all or User.new without loading the class as it has been preloaded by rails console already

How to write tests for ActiveRecord extension gem

You probably want to have a look at acts_as_fu gem: https://github.com/nakajima/acts_as_fu.

Btw, you can use db in your rspec tests, but you don;t want to do this to test extensions.

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