Class: Module

Inherits:
Object
  • Object
show all
Defined in:
lib/everythingrb/core/module.rb

Instance Method Summary collapse

Instance Method Details

#attr_predicate(*attributes) ⇒ nil

Creates predicate (boolean) methods that return true/false Similar to attr_reader, attr_writer, etc. Designed to work with regular classes, Struct, and Data objects.

Examples:

With a regular class

class User
  attr_predicate :admin
  attr_accessor :admin
end

user = User.new
user.admin? # => false
user.admin = true
user.admin? # => true

With Struct/Data

Person = Struct.new(:active)
Person.attr_predicate(:active)

person = Person.new(active: true)
person.active? # => true

Parameters:

  • *attributes (Array<Symbol, String>) —

    Attribute names

Returns:

  • (nil)

Raises:

  • (ArgumentError) —

    If a predicate method of the same name already exists



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# File 'lib/everythingrb/core/module.rb', line 33

def attr_predicate(*attributes)
  attributes.each do |attribute|
    if method_defined?(:"#{attribute}?")
      raise ArgumentError, "Cannot create predicate method on #{self.class} - #{attribute}? is already defined. Please choose a different name or remove the existing method."
    end

    module_eval <<-STR, __FILE__, __LINE__ + 1
      def #{attribute}?
        if instance_variable_defined?(:@#{attribute})
          !!@#{attribute}
        elsif respond_to?(:#{attribute})
          !!self.#{attribute}
        else
          false
        end
      end
    STR
  end

  nil
end