SafeFinder

SafeFinder lets you define a model's Null Object through a simple DSL, and returns that when you don't find an instance of that model.

Installation

Add this line to your application's Gemfile:

gem 'safe_finder'

And then execute:

$ bundle

Or install it yourself as:

$ gem install safe_finder

Usage

Basic

Let's say you have a Post class, and it has title and content column.

First, you need to include SafeFinder in your model:

class Post < ActiveRecord::Base
  include SafeFinder
end

Now you can query like this, and if it doesn't find anything it returns a Null Object:

# It returns a Null Object
null_object = Post.safely.find_by_title("Not Exists")

null_object.class   # NullPost
null_object.title   # nil
null_object.content # nil

Custom Attributes and Methods

And you can customize the Null Object's attributes or methods using a DSL:

class Post < ActiveRecord::Base
  include SafeFinder
  
  safe_attribute :title, "Null"
  safe_method :some_method do
    "Do Something"
  end
end

null_object = Post.safely.find_by_title("Not Exists")
null_object.title # "Null"
null_object.some_method # "Do Something"

Get a Null Object directly

Just simply use:

Post.null_object # <NullPost:0x007fa8a4713be0>

Inheritance

All Null Objects inherit SafeFinder::NullObject, so you can add it in

app/models/safe_finder/null_object.rb

by generate it with

rails g safe_finder:model

and define general methods for every Null Object

module SafeFinder
  class NullObject
    def hello
      "Hello"
    end
  end
end

null_object = Post.null_object
null_object.hello # "Hello"

TODOs

• Add association support, like user.post should also returns Null Object when it's nil
• More use cases in readme

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.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/st0012/SafeFinder.