Predicateable

Predicateable is a Ruby mixin that dynamically defines predicate methods (like admin?, young?) based on the return value of a method. It's ideal for cleanly querying symbolic states without writing repetitive predicate methods.

Features

• Defines ? predicate methods dynamically.
• Supports prefixing (e.g. account_type_admin?).
• strict: option ensures only symbols are matched.
• Works seamlessly with respond_to?.
• Pure Ruby, no dependencies.

Installation

Add this line to your Gemfile:

gem "predicateable"

And run:

bundle install

Or install it directly:

gem install predicateable

Usage

Basic Example

class User
  include Predicateable

  attr_reader :age, :account_type

  predicate :age_group, [:young, :middle, :old]
  predicate :account_type, [:guest, :member, :admin], prefix: true

  def initialize(age:, account_type:)
    @age = age
    @account_type = account_type
  end

  def age_group
    case age
    when 0...30 then :young
    when 30...60 then :middle
    else :old
    end
  end
end

user = User.new(age: 45, account_type: :admin)

user.middle?                # => true
user.age_group              # => :middle
user.account_type_admin?    # => true
user.account_type_guest?    # => false

Strict Mode

If you want predicate checks to pass only when the method returns a Symbol, enable strict: true:

class User
  include Predicateable

  attr_reader :role

  predicate :role, [:editor, :viewer], strict: true

  def initialize(role:)
    @role = role
  end
end

User.new(role: :editor).editor?  # => true
User.new(role: "editor").editor? # => false (strict mode)

Behavior Summary

Feature	Description
prefix:	Adds method name prefix (e.g. account_type_)
strict:	Only matches Symbol values
respond_to?	Works with predicate methods
NoMethodError	Raised when calling undefined predicates

Testing

This gem uses Minitest. To run tests:

bundle exec rake test

Contributing

Bug reports and pull requests are welcome! If you have ideas for improvement or questions, feel free to open an issue.

License

This project is licensed under the MIT License. See the LICENSE.txt file for details.