Module: NRSER::Meta::ClassAttrs::ClassMethods

Defined in:
lib/nrser/meta/class_attrs.rb

Overview

Class methods to extend the receiver with when NRSER::Meta::ClassAttrs is included.

Instance Method Summary collapse

Instance Method Details

#class_attr_accessor(attr, default: NRSER::NO_ARG, default_from: NRSER::NO_ARG) ⇒ Object 



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# File 'lib/nrser/meta/class_attrs.rb', line 75

def class_attr_accessor attr,
                        default: NRSER::NO_ARG,
                        default_from: NRSER::NO_ARG
  
  var_name = "@#{ attr }".to_sym
  
  singleton_class.class_eval do
    define_method(attr) do |*args|
      case args.length
      when 0
        instance_variable_lookup  var_name,
                                  default: default,
                                  default_from: default_from
      when 1
        instance_variable_set var_name, args[0]
      else
        raise ArgumentError.new NRSER.squish "wrong number of arguments\n(given \#{ args.length }, expected 0 or 1)\n"
      end
    end
    
    define_method("#{ attr }=") do |value|
      instance_variable_set var_name, value
    end
  end
end

#class_attr_writer(attr) ⇒ Object 



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# File 'lib/nrser/meta/class_attrs.rb', line 104

def class_attr_writer attr
  var_name = "@#{ attr }".to_sym
  
  singleton_class.class_eval do
    define_method("#{ attr }=") do |value|
      instance_variable_set var_name, value
    end
  end
end

#instance_variable_lookup(name, default: NRSER::NO_ARG, default_from: NRSER::NO_ARG) ⇒ Object 



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# File 'lib/nrser/meta/class_attrs.rb', line 28

def instance_variable_lookup  name,
                              default: NRSER::NO_ARG,
                              default_from: NRSER::NO_ARG
  
  # If it's defined here on self, return that
  if instance_variable_defined? name
    return instance_variable_get name
  end
  
  # Ok, now to need to look for it.
  
  # See if the superclass has the lookup method
  if superclass.respond_to? :instance_variable_lookup
    # It does. See what we get from that. We create a new object to use
    # as a flag and assign it to `default` so we can tell if the search
    # failed.
    not_found = Object.new
    result = superclass.instance_variable_lookup name, default: not_found
    
    # If we found something, return it.
    return result unless result == not_found
    
  end # if superclass.respond_to? :instance_variable_lookup
  
  # Ok, nothing was found.
  
  # See if we can use a default...
  if default != NRSER::NO_ARG || default_from != NRSER::NO_ARG
    # We can use a default.
    # `default` takes precedence.
    if default != NRSER::NO_ARG
      default
    else
      send default_from
    end
    
  else
    # Nope, we can't, raise.
    raise NoMethodError.new NRSER.squish "\#{ name.inspect } is not defined anywhere in the class hierarchy\n"

  end # if we have a default value / else
  
end