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Ruby String to Nom de la classe

J'essaie de créer une nouvelle classe héritant de ActiveRecord::Base. La classe doit être générée dynamiquement à partir d'une chaîne.

"general_systems".camelize.singularize = Class.new < ActiveRecord::Base

Cependant, je continue à avoir l'erreur:

undefined method `singularize=' for "GeneralSystems":String

J'ai aussi essayé de constantize la chaîne

>> foo = "general_systems".camelize.singularize
=> "GeneralSystem"
>> foo.constantize
NameError: uninitialized constant GeneralSystem
    from /var/lib/gems/1.9.1/gems/activesupport-3.0.5/lib/active_support/inflector/methods.rb:124:in `block in constantize'
    from /var/lib/gems/1.9.1/gems/activesupport-3.0.5/lib/active_support/inflector/methods.rb:123:in `each'
    from /var/lib/gems/1.9.1/gems/activesupport-3.0.5/lib/active_support/inflector/methods.rb:123:in `constantize'
    from /var/lib/gems/1.9.1/gems/activesupport-3.0.5/lib/active_support/core_ext/string/inflections.rb:43:in `constantize'
    from (irb):4
    from /usr/bin/irb:12:in `<main>'
>> foo.constantize = Class.new
NoMethodError: undefined method `constantize=' for "GeneralSystem":String
    from (irb):5
    from /usr/bin/irb:12:in `<main>'

Toute aide serait grandement appréciée.

rubymetaprogramming
34
Telmo

Si vous utilisez Rails, il fournit une méthode appelée #constantize qui fonctionnera:

irb(main):017:0> Object.const_get 'House::Owns'
NameError: wrong constant name House::Owns

'House::Owns'.constantize
=> House::Owns
33
Peter Ehrlich

Quelque chose comme ça?

>> Object.const_set("general_systems".classify, Class.new)
=> GeneralSystem
>> GeneralSystem.new
=> #<GeneralSystem:0x105b0f738>
32
Michael Kohl
klazz = Class.new(ActiveRecord::Base) do
  def do_something_fun(param1)
    param1.have_fun!
  end
end

klazz_name = "general_systems".singularize.classify
Object.const_set(klazz_name, klazz)
13
yfeldblum

Regardez cet exemple de "The Book Of Ruby", inclus dans l'installateur de Ruby 1.9.

puts("What shall we call this class?> ")
className = gets.strip().capitalize()
Object.const_set(className,Class.new)
puts("I'll give it a method called > 'myname'" ) 
className = Object.const_get(className)
className::module_eval{
  define_method(:myname){ 
    puts("The name of my class is '#{self.class}'" ) 
 } }
 x = className.new x.myname
8
AShelly

Si votre chaîne contient un espace de noms, vous pouvez utiliser: 

require 'rubygems'
require 'active_support/inflector'
parent=String # using String to get a self contained example
# require 'active_record'   # uncomment for ActiveRecord::Base as parent class
# parent=ActiveRecord::Base # uncomment for ActiveRecord::Base as parent class
namespace = 'A::B::general_systems'.split('::') 
class_name = namespace.pop 
namespace = namespace.inject(Object) do |mod, name|
  if mod.constants.collect{|sym| sym.to_s}.include? name.classify
    mod.const_get name.classify
  else
    mod.const_set name.classify, Module.new
  end
end

klass = if namespace.constants.include? class_name.classify
  namespace.const_get class_name.classify
else
  namespace.const_set class_name.classify, Class.new(parent)
end

object = klass.allocate # allocate new object of klass
object.send :initialize # initialize object
object.class
object.class.superclass
4
Florian Feldhaus

Donné:

class Banana
end

Vous pouvez aller chercher la classe en simple Ruby avec:

Object.const_get 'Banana'
=> Banana

ou si vous utilisez Rails:

'Banana'.constantize
=> Banana
0
Connor