Initial commit

.gitignore

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+/.bundle/
+/.yardoc
+/Gemfile.lock
+/_yardoc/
+/coverage/
+/doc/
+/pkg/
+/spec/reports/
+/tmp/

.rspec

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+--format documentation
+--color

.travis.yml

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+sudo: false
+language: ruby
+rvm:
+  - 2.2.2
+before_install: gem install bundler -v 1.13.1

Gemfile

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+source 'https://rubygems.org'
+
+# Specify your gem's dependencies in use_case_pattern.gemspec
+gemspec

README.md

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+# UseCasePattern
+
+A module that helps you to implement the Use Case design pattern.
+
+## Installation
+
+Add this line to your application's Gemfile:
+
+```ruby
+gem 'use_case_pattern'
+```
+
+And then execute:
+
+    $ bundle
+
+Or install it yourself as:
+
+    $ gem install use_case_pattern
+
+## Usage
+
+TODO: Write usage instructions here
+
+## Development
+
+After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.
+
+To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).
+
+## Contributing
+
+Bug reports and pull requests are welcome on GitHub at https://github.com/abletech/use_case_pattern.

Rakefile

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+require "bundler/gem_tasks"
+require "rspec/core/rake_task"
+
+RSpec::Core::RakeTask.new(:spec)
+
+task :default => :spec

bin/console

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+#!/usr/bin/env ruby
+
+require "bundler/setup"
+require "use_case_pattern"
+
+# You can add fixtures and/or initialization code here to make experimenting
+# with your gem easier. You can also use a different console, if you like.
+
+# (If you use this, don't forget to add pry to your Gemfile!)
+# require "pry"
+# Pry.start
+
+require "irb"
+IRB.start

bin/setup

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+#!/usr/bin/env bash
+set -euo pipefail
+IFS=$'\n\t'
+set -vx
+
+bundle install
+
+# Do any other automated setup that you need to do here

lib/use_case_pattern.rb

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+require "use_case_pattern/version"
+require "use_case_pattern/base"
+
+module UseCasePattern
+  def self.included(receiver)
+    receiver.send :include, UseCasePattern::Base
+  end
+end

lib/use_case_pattern/base.rb

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+require "active_support"
+require "active_model"
+
+module UseCasePattern
+  module Base
+    extend ActiveSupport::Concern
+    include ActiveModel::Validations
+
+    module ClassMethods
+      # The perform method of a UseCase should always return itself
+      def perform(*args)
+        new(*args).tap { |use_case| use_case.perform }
+      end
+
+      # raise an exception if perform generates any errors
+      def perform!(*args)
+        new(*args).tap { |use_case| use_case.perform! }
+      end
+    end
+
+    # implement all the steps required to complete this use case
+    def perform
+      raise NotImplementedError
+    end
+
+    def perform!
+      perform
+
+      if failure?
+        raise "Unexpected error #{errors.full_messages.join(', ')}"
+      end
+    end
+
+    # inside of perform, add errors if the use case did not succeed
+    def success?
+      errors.none?
+    end
+
+    def failure?
+      errors.any?
+    end
+  end
+end

lib/use_case_pattern/version.rb

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+module UseCasePattern
+  VERSION = "1.0.0"
+end

spec/spec_helper.rb

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+$LOAD_PATH.unshift File.expand_path("../../lib", __FILE__)
+require "use_case_pattern"

spec/use_case_pattern/base_spec.rb

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+require "spec_helper"
+
+describe UseCasePattern::Base do
+  describe "#perform" do
+    context "when the including class has defined a perform method" do
+      it "should call the perform method" do
+        expect(SimpleUseCase).to receive(:perform)
+        SimpleUseCase.perform
+      end
+    end
+
+    context "when the including class has defined a perform method and initializer" do
+      subject(:use_case){ UseCaseWithConstructor.perform(10) }
+
+      it "should call the initializer" do
+        expect(UseCaseWithConstructor).to receive(:new).with(10).and_call_original
+        use_case
+      end
+
+      it "should have no errors" do
+        expect(use_case.errors.full_messages).to eq([])
+      end
+    end
+  end
+end
+
+class SimpleUseCase
+  include UseCasePattern
+
+  def perform
+  end
+end
+
+class UseCaseWithConstructor
+  include UseCasePattern
+
+  def initialize(args)
+    @args = args
+  end
+
+  def perform
+  end
+end

spec/use_case_pattern_spec.rb

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+require "spec_helper"
+
+describe UseCasePattern do
+  it "has a version number" do
+    expect(UseCasePattern::VERSION).not_to be nil
+  end
+end

use_case_pattern.gemspec

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+# coding: utf-8
+lib = File.expand_path('../lib', __FILE__)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+require 'use_case_pattern/version'
+
+Gem::Specification.new do |spec|
+  spec.name          = "use_case_pattern"
+  spec.version       = UseCasePattern::VERSION
+  spec.authors       = ["Nigel Ramsay"]
+  spec.email         = ["[email protected]"]
+
+  spec.summary       = "A module that helps you to implement the Use Case design pattern"
+  spec.description   = "A module that helps you to implement the Use Case design pattern"
+  spec.homepage      = "https://github.com/abletech/use_case_pattern"
+
+  spec.files         = `git ls-files -z`.split("\x0").reject do |f|
+    f.match(%r{^(test|spec|features)/})
+  end
+
+  spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
+  spec.require_paths = ["lib"]
+
+  spec.required_ruby_version = '~> 2.0'
+
+  spec.add_runtime_dependency "activemodel", [">= 4.0.0", "~> 5.0.0"]
+  spec.add_runtime_dependency "activesupport", [">= 4.0.0", "~> 5.0.0"]
+
+  spec.add_development_dependency "bundler", "~> 1.13"
+  spec.add_development_dependency "rake", "~> 10.0"
+  spec.add_development_dependency "rspec", "~> 3.0"
+end