# TemplateParams Runtime type-check for **template preconditions**, including instance variables and local variables. Think of this as the method signature of a template, as the **documentation**. ## Installation 1. Add it to your Gemfile and run `bundle`. ```ruby gem 'template_params' ``` 2. If you're using rails, add a helper method. ```ruby # app/helpers/application_helper.rb def template_param(*args, &block) ::TemplateParams::Assertion.assert(*args, &block) end ``` If you're not using rails, let me know how you install it, and I'll put that here. ## Usage ```ruby # Assert `poll` is defined. If not, raises an `ArgumentError` (the "arguments" # of the template are invalid). template_param { poll } # Assert `@course` is defined. Meaningless because instance variables are # always defined. template_param { @course } # Assert `poll.is_a?(::Poll)`. If not, raises a `TypeError`. template_param(::Poll) { poll } # Assert `@course.is_a?(::Course)` template_param(::Course) { @course } # Assert `@course` is either a `::Course` or `nil` template_param(::Course, allow_nil: true) { @course } ``` ## Development After checking out the repo, run `bin/setup` to install dependencies. Then, run `bundle exec rspec` 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/[USERNAME]/template_assertions. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](contributor-covenant.org) code of conduct. ## License The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).