Spawn

A ridiculously simple fixtures replacement for your web framework of choice.

Spawn is a very small library that can effectively replace fixtures or any other huge library for the same task.

In the examples below we are using Faker to generate random data, but you can use any method.

Note that the object the spawner block yields is not an instance of User, but an OpenStruct that records the attributes passed and will in turn relay that information when the User is instantiated.

With ActiveRecord:

class User < ActiveRecord::Base
  spawner do |user|
    user.name = Faker::Name.name
    user.email = Faker::Internet.email
  end
end

With Sequel:

class User < Sequel::Model
  extend Spawn

  spawner do |user|
    user.name = Faker::Name.name
    user.email = Faker::Internet.email
  end
end

With Ohm:

class User < Ohm::Model
  extend Spawn

  attribute :name
  attribute :email

  spawner do |user|
    user.name = Faker::Name.name
    user.email = Faker::Internet.email
  end
end

If you don't want to pollute your class definition, you can of course use it from outside:

User.spawner do |user|
  user.name = Faker::Name.name
  user.email = Faker::Internet.email
end

Then, in your test or in any other place:

@user = User.spawn

Or, if you need something special:

@user = User.spawn :name => "Michel Martens"

This sends to User.new all the attributes defined in the spawner block, along with the hash of attributes passed when spawning.

If you want a reference to the model before the validity is checked, you can pass a block:

@user = User.spawn { |u| u.name = "Michel Martens" }

Spawn will execute the right hand side of your assignment even if you provide a value for some particular key. Consider the following example:

User.spawner do |user|
  user.profile = Profile.spawn # Profile.spawn is executed even if you provide a value for :profile.
end

User.spawn(:profile => Profile.first)

Here, you will be creating an extra instance of Profile, because when the block is evaluated it calls Profile.spawn. If the right hand side of your assignment is costly or has side effects, you may want to avoid this behavior by using ||=:

User.spawner do |user|
  user.profile ||= Profile.spawn
end

Then, if you pass a :profile:

User.spawn(:profile => Profile.first)

You can verify that Profile.spawn is never called. Although this may sound evident, it can bite you if you rely on the RHS not executing (e.g. if you're using Spawn to populate fake data into a database and you want to control how many instances you create).

$ sudo gem install spawn

Thanks to Foca, Pedro and Diego for the suggestions and improvements to this tiny library.

Copyright (c) 2009 Michel Martens and Damian Janowski

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.