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# frozen_string_literal: true
module Dry
module Core
# Class for generating more classes
class ClassBuilder
ParentClassMismatch = Class.new(TypeError)
attr_reader :name, :parent, :namespace
def initialize(name:, parent: nil, namespace: nil)
@name = name
@namespace = namespace
@parent = parent || Object
end
# Generate a class based on options
#
# @example Create anonymous class
# builder = Dry::Core::ClassBuilder.new(name: 'MyClass')
#
# klass = builder.call
# klass.name # => "MyClass"
#
# @example Create named class
# builder = Dry::Core::ClassBuilder.new(name: 'User', namespace: Entities)
#
# klass = builder.call
# klass.name # => "Entities::User"
# klass.superclass.name # => "Entities::User"
# Entities::User # => "Entities::User"
# klass.superclass == Entities::User # => true
#
# @return [Class]
def call
klass = if namespace
create_named
else
create_anonymous
end
yield(klass) if block_given?
klass
end
private
# @api private
def create_anonymous
klass = Class.new(parent)
name = self.name
klass.singleton_class.class_eval do
define_method(:name) { name }
alias_method :inspect, :name
alias_method :to_s, :name
end
klass
end
# @api private
def create_named
name = self.name
base = create_base(namespace, name, parent)
klass = Class.new(base)
namespace.module_eval do
remove_const(name)
const_set(name, klass)
remove_const(name)
const_set(name, base)
end
klass
end
# @api private
def create_base(namespace, name, parent)
begin
namespace.const_get(name)
rescue NameError # rubocop:disable Lint/SuppressedException
end
if namespace.const_defined?(name, false)
existing = namespace.const_get(name)
unless existing <= parent
raise ParentClassMismatch, "#{existing.name} must be a subclass of #{parent.name}"
end
existing
else
klass = Class.new(parent || Object)
namespace.const_set(name, klass)
klass
end
end
end
end
end
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