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Gary Weaver

2012-Sep-13 17:04 UTC

Wierdness with dependency resolution with models in modules

I''m sure this is some basic misunderstanding I have to how dependency 
resolution should work in Rails, but am experiencing some wierdness with 
modules and models.

I hadn''t been using modules for models much because I had run into
early
issues with them, but woke up early this morning with the idea of a way to 
use them for something that we need.

This was in a brand new Rails 4.0 beta project (using github rails/rails 
master), but have the same behavior in Rails 3.2.6.

Here are the models. I just wanted to try to have the class load so I could 
see which class was being loaded, but just referencing these model classes 
causes issues:

app/models/associated_model.rb

class AssociatedModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end

app/models/my_model.rb

class MyModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end

app/models/root_only_model.rb

class RootOnlyModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end

app/models/some_module/associated_model.rb

class SomeModule::AssociatedModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
#bug
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end

app/models/some_module/module_specific_model.rb

module SomeModule
  class ModuleSpecificModel < ActiveRecord::Base
    puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
    puts "in #{self.name}, ModuleSpecificModel is 
#{ModuleSpecificModel.name}"
    puts "in #{self.name}, MyModel is #{MyModel.name}"
    puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
  end
end

app/models/some_module/my_model.rb

class SomeModule::MyModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end

And here is what happens in rails console:

$ rails c
Loading development environment (Rails 4.0.0.beta)
1.9.3p194 :001 > AssociatedModel
in AssociatedModel, AssociatedModel is AssociatedModel
NameError: uninitialized constant AssociatedModel::ModuleSpecificModel
  from /path/to/new_rails_app/app/models/associated_model.rb:3:in 
`<class:AssociatedModel>''
  from /path/to/new_rails_app/app/models/associated_model.rb:1:in `<top 
(required)>''
  from (irb):1
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top 
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''
1.9.3p194 :002 > MyModel
in AssociatedModel, AssociatedModel is AssociatedModel
NameError: uninitialized constant AssociatedModel::ModuleSpecificModel
  from /path/to/new_rails_app/app/models/associated_model.rb:3:in 
`<class:AssociatedModel>''
  from /path/to/new_rails_app/app/models/associated_model.rb:1:in `<top 
(required)>''
  from /path/to/new_rails_app/app/models/my_model.rb:2:in
`<class:MyModel>''
  from /path/to/new_rails_app/app/models/my_model.rb:1:in `<top
(required)>''
  from (irb):2
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top 
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''
1.9.3p194 :003 > RootOnlyModel
in AssociatedModel, AssociatedModel is AssociatedModel
NameError: uninitialized constant AssociatedModel::ModuleSpecificModel
  from /path/to/new_rails_app/app/models/associated_model.rb:3:in 
`<class:AssociatedModel>''
  from /path/to/new_rails_app/app/models/associated_model.rb:1:in `<top 
(required)>''
  from /path/to/new_rails_app/app/models/root_only_model.rb:2:in 
`<class:RootOnlyModel>''
  from /path/to/new_rails_app/app/models/root_only_model.rb:1:in `<top 
(required)>''
  from (irb):3
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top 
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''
1.9.3p194 :004 > SomeModule::AssociatedModel
NameError: uninitialized constant 
SomeModule::AssociatedModel::AssociatedModel
  from 
/path/to/new_rails_app/app/models/some_module/associated_model.rb:2:in 
`<class:AssociatedModel>''
  from 
/path/to/new_rails_app/app/models/some_module/associated_model.rb:1:in 
`<top (required)>''
  from (irb):4
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top 
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''
1.9.3p194 :005 > SomeModule::ModuleSpecificModel
NameError: uninitialized constant 
SomeModule::AssociatedModel::AssociatedModel
  from 
/path/to/new_rails_app/app/models/some_module/associated_model.rb:2:in 
`<class:AssociatedModel>''
  from 
/path/to/new_rails_app/app/models/some_module/associated_model.rb:1:in 
`<top (required)>''
  from 
/path/to/new_rails_app/app/models/some_module/module_specific_model.rb:3:in 
`<class:ModuleSpecificModel>''
  from 
/path/to/new_rails_app/app/models/some_module/module_specific_model.rb:2:in 
`<module:SomeModule>''
  from 
/path/to/new_rails_app/app/models/some_module/module_specific_model.rb:1:in 
`<top (required)>''
  from (irb):5
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top 
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''
1.9.3p194 :006 > SomeModule::MyModel
NameError: uninitialized constant 
SomeModule::AssociatedModel::AssociatedModel
  from 
/path/to/new_rails_app/app/models/some_module/associated_model.rb:2:in 
`<class:AssociatedModel>''
  from 
/path/to/new_rails_app/app/models/some_module/associated_model.rb:1:in 
`<top (required)>''
  from /path/to/new_rails_app/app/models/some_module/my_model.rb:2:in 
`<class:MyModel>''
  from /path/to/new_rails_app/app/models/some_module/my_model.rb:1:in `<top 
(required)>''
  from (irb):6
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in 
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top 
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''

Thanks in advance,
Gary

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Gary Weaver

2012-Sep-13 17:07 UTC

head link

Re: Wierdness with dependency resolution with models in modules

Note: I understand that referring to models in a module from a model in the 
no module (in app/models) would not work without declaring those as 
SomeModule::SomeModelClassName, but I was confused about the other things I 
thought would have resolved because I thought that it was supposed to 
search parent modules for the constant if not found.

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Jonathan Lozinski

2012-Sep-13 17:43 UTC

head link

Re: Wierdness with dependency resolution with models in modules

This doesn''t look like a rails issue.  It looks like ruby expected
behaviour, unless I misunderstand.

The constant ModuleSpecificModel doesn''t exist.  Only
SomeModule::ModuleSpecificModel exists.  Ruby auto loading or rails
autoloading would not expect this code to ''install'' the
ModuleSpecificModule at the top level ( I.e ::ModuleSpecificModel )

Sent from my iPad

On 13 Sep 2012, at 18:04, Gary Weaver <garysweaver@gmail.com> wrote:

I''m sure this is some basic misunderstanding I have to how dependency
resolution should work in Rails, but am experiencing some wierdness with
modules and models.

I hadn''t been using modules for models much because I had run into
early
issues with them, but woke up early this morning with the idea of a way to
use them for something that we need.

This was in a brand new Rails 4.0 beta project (using github rails/rails
master), but have the same behavior in Rails 3.2.6.

Here are the models. I just wanted to try to have the class load so I could
see which class was being loaded, but just referencing these model classes
causes issues:

app/models/associated_model.rb

class AssociatedModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end

app/models/my_model.rb

class MyModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end

app/models/root_only_model.rb

class RootOnlyModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end

app/models/some_module/associated_model.rb

class SomeModule::AssociatedModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
#bug
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end

app/models/some_module/module_specific_model.rb

module SomeModule
  class ModuleSpecificModel < ActiveRecord::Base
    puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
    puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
    puts "in #{self.name}, MyModel is #{MyModel.name}"
    puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
  end
end

app/models/some_module/my_model.rb

class SomeModule::MyModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end

And here is what happens in rails console:

$ rails c
Loading development environment (Rails 4.0.0.beta)
1.9.3p194 :001 > AssociatedModel
in AssociatedModel, AssociatedModel is AssociatedModel
NameError: uninitialized constant AssociatedModel::ModuleSpecificModel
  from /path/to/new_rails_app/app/models/associated_model.rb:3:in
`<class:AssociatedModel>''
  from /path/to/new_rails_app/app/models/associated_model.rb:1:in `<top
(required)>''
  from (irb):1
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''
1.9.3p194 :002 > MyModel
in AssociatedModel, AssociatedModel is AssociatedModel
NameError: uninitialized constant AssociatedModel::ModuleSpecificModel
  from /path/to/new_rails_app/app/models/associated_model.rb:3:in
`<class:AssociatedModel>''
  from /path/to/new_rails_app/app/models/associated_model.rb:1:in `<top
(required)>''
  from /path/to/new_rails_app/app/models/my_model.rb:2:in
`<class:MyModel>''
  from /path/to/new_rails_app/app/models/my_model.rb:1:in `<top
(required)>''
  from (irb):2
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''
1.9.3p194 :003 > RootOnlyModel
in AssociatedModel, AssociatedModel is AssociatedModel
NameError: uninitialized constant AssociatedModel::ModuleSpecificModel
  from /path/to/new_rails_app/app/models/associated_model.rb:3:in
`<class:AssociatedModel>''
  from /path/to/new_rails_app/app/models/associated_model.rb:1:in `<top
(required)>''
  from /path/to/new_rails_app/app/models/root_only_model.rb:2:in
`<class:RootOnlyModel>''
  from /path/to/new_rails_app/app/models/root_only_model.rb:1:in `<top
(required)>''
  from (irb):3
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''
1.9.3p194 :004 > SomeModule::AssociatedModel
NameError: uninitialized constant
SomeModule::AssociatedModel::AssociatedModel
  from
/path/to/new_rails_app/app/models/some_module/associated_model.rb:2:in
`<class:AssociatedModel>''
  from
/path/to/new_rails_app/app/models/some_module/associated_model.rb:1:in
`<top (required)>''
  from (irb):4
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''
1.9.3p194 :005 > SomeModule::ModuleSpecificModel
NameError: uninitialized constant
SomeModule::AssociatedModel::AssociatedModel
  from
/path/to/new_rails_app/app/models/some_module/associated_model.rb:2:in
`<class:AssociatedModel>''
  from
/path/to/new_rails_app/app/models/some_module/associated_model.rb:1:in
`<top (required)>''
  from
/path/to/new_rails_app/app/models/some_module/module_specific_model.rb:3:in
`<class:ModuleSpecificModel>''
  from
/path/to/new_rails_app/app/models/some_module/module_specific_model.rb:2:in
`<module:SomeModule>''
  from
/path/to/new_rails_app/app/models/some_module/module_specific_model.rb:1:in
`<top (required)>''
  from (irb):5
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''
1.9.3p194 :006 > SomeModule::MyModel
NameError: uninitialized constant
SomeModule::AssociatedModel::AssociatedModel
  from
/path/to/new_rails_app/app/models/some_module/associated_model.rb:2:in
`<class:AssociatedModel>''
  from
/path/to/new_rails_app/app/models/some_module/associated_model.rb:1:in
`<top (required)>''
  from /path/to/new_rails_app/app/models/some_module/my_model.rb:2:in
`<class:MyModel>''
  from /path/to/new_rails_app/app/models/some_module/my_model.rb:1:in `<top
(required)>''
  from (irb):6
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in
`start''
  from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top
(required)>''
  from script/rails:6:in `require''
  from script/rails:6:in `<main>''

Thanks in advance,
Gary

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Gary Weaver

2012-Sep-13 17:47 UTC

head link

Re: Wierdness with dependency resolution with models in modules

I should have fixed the models before posting, but these are the models 
that I would have thought would work with the module identifiers set 
properly.

It looks like when a model class in a module refers to by class name only, 
which I think is supposed to work, it tries to use its fully-qualified 
class name as its module instead of its module. Is that a bug or something 
I''m doing wrong?

So, basically this is the wierdness:

Loading development environment (Rails 4.0.0.beta)
1.9.3p194 :001 > AssociatedModel
in AssociatedModel, AssociatedModel is AssociatedModel
in SomeModule::ModuleSpecificModel, AssociatedModel is AssociatedModel
NameError: uninitialized constant 
SomeModule::ModuleSpecificModel::ModuleSpecificModel
    from 
/path/to/spike/app/models/some_module/module_specific_model.rb:3:in 
`<class:ModuleSpecificModel>''
    from 
/path/to/spike/app/models/some_module/module_specific_model.rb:1:in `<top 
(required)>''
    from /path/to/spike/app/models/associated_model.rb:3:in 
`<class:AssociatedModel>''
    from /path/to/spike/app/models/associated_model.rb:1:in `<top 
(required)>''
    from (irb):1
    from /path/to/github/rails/railties/lib/rails/commands/console.rb:78:in 
`start''
    from /path/to/github/rails/railties/lib/rails/commands/console.rb:9:in 
`start''
    from /path/to/github/rails/railties/lib/rails/commands.rb:47:in `<top 
(required)>''
    from script/rails:6:in `require''
    from script/rails:6:in `<main>''

$ find app/models -exec more {} \;
app/models is a directory
class AssociatedModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is 
#{SomeModule::ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end
class MyModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is 
#{SomeModule::ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end
class RootOnlyModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is 
#{SomeModule::ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end
app/models/some_module is a directory
class SomeModule::AssociatedModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end
class SomeModule::ModuleSpecificModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end
class SomeModule::MyModel < ActiveRecord::Base
  puts "in #{self.name}, AssociatedModel is #{AssociatedModel.name}"
  puts "in #{self.name}, ModuleSpecificModel is
#{ModuleSpecificModel.name}"
  puts "in #{self.name}, MyModel is #{MyModel.name}"
  puts "in #{self.name}, RootOnlyModel is #{RootOnlyModel.name}"
end


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Gary Weaver

2012-Sep-13 17:56 UTC

head link

Re: Wierdness with dependency resolution with models in modules

On Thursday, September 13, 2012 1:43:22 PM UTC-4, mrloz
wrote:>
> This doesn''t look like a rails issue.  It looks like ruby expected
> behaviour, unless I misunderstand.
>
> The constant ModuleSpecificModel doesn''t exist.  Only 
> SomeModule::ModuleSpecificModel exists.  Ruby auto loading or rails 
> autoloading would not expect this code to ''install'' the 
> ModuleSpecificModule at the top level ( I.e ::ModuleSpecificModel )
>
Thanks!

When perusing activesupport/lib/activesupport/dependencies.rb, I had 
assumed that if you were in the same module as the class (or in the last 
example, within the class itself) that it would attempt to find that class 
in the current module even if you didn''t specify a module, but it
doesn''t
seem like it should be looking for: 
SomeModule::ModuleSpecificModel::ModuleSpecificModel when referring to 
ModuleSpecificModel within the ModuleSpecificModel class itself.

But I think my confusion was assuming that there is a different from a 
constant that is a class and a constant that is some other type. That is 
the Java side of my brain interfering.

Sorry to bother about this. I was hoping that dependency resolution could 
be used to refer to a model class from another model class and it 
automatically find it in the root module if it didn''t exist in the
current
module, but I had forgotten about other types of constants and how that 
would throw a wrench in things if it worked that way.

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Xavier Noria

2012-Sep-13 21:25 UTC

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Re: Wierdness with dependency resolution with models in modules

The problem you are seeing can be summarized in this snippet:

    module M
    end

    class M::A
      A
    end

If you run that code with plain Ruby you''ll get

    uninitialized constant M::A::A (NameError)

Let''s see why that''s that way in Ruby first, then we will go
with
dependencies.rb.

Ruby looks for constants in the nesting, then ancestors, then in Object if
the container module is a module, and fallbacks to const_missing if
present. That''s the resolution algorithm quickly described.

OK, the nesting at the point where we evaluate A is [M::A]. The class and
module keywords push to the nesting the module object they are creating or
reopening. That is one module object regardless of the constant or constant
path that yielded it. If the constant path is composed of 15 constants, in
the end it evaluates to one single class or module object, that''s the
one
pushed to the nesting.

In particular, M does not belong to the nesting.

So Ruby goes like this: A does not belong to M::A (nesting scan done), A
does not belong to any of [Object, Kernel, BasicObject] (ancestors scan
done). Since the containing M::A is a class we do not do the extra Object
check. And finally const_missing is not present. Therefore: NameError.

The key point here is that A belongs to M, and M is not in the nesting.

Now, Active Support is not able to discern whether M belongs or does not
belong to the nesting because Ruby does not tell you in const_missing. AS
assumes the nesting matches the name of the class or module const_missing
was triggered in. In the example about that would be, [M::A, M].

But, when const_missing is triggered dependencies.rb manually checks if the
constant is present in one of those "parent" modules. So, what happens
in
Rails is that const_missing is triggered, and dependencies.rb is able to
see that A is defined in M, therefore a posteriori M must not belong to the
nesting because otherwise const_missing had not been triggered in the first
place, and is able to raise a NameError, which is the correct answer.

Constant autoloading in Rails does *not* emulate the constant name
resolution algorithm. But in this case it behaves as Ruby.

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Gary Weaver

2012-Sep-13 22:19 UTC

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Re: Wierdness with dependency resolution with models in modules

On Thursday, September 13, 2012 5:26:29 PM UTC-4, Xavier Noria wrote:
> Constant autoloading in Rails does *not* emulate the constant name 
> resolution algorithm. But in this case it behaves as Ruby.
>
>  Thanks! All of that was a great summary and I appreciate your time for 
making it so clear.

How I went down that bad road:

Imagine a world where Rails constant resolution took the current module of 
the class that is referring to the class into account when def 
load_missing_constant(from_mod, const_name) was doing its thing, such that 
if you refer to a class from a controller that was in a module or a model 
that was in a module, it would get the one in the same module if it 
existed, if not then its parent module, etc. up to root. To refer to a 
class in the root module, a module call Root could exist to do 
Root::SomeClass.

In this roller coaster ride through fantasyland... the following could 
happen (even though it won''t, this is 200 proof unicorns and rainbows):

* in the controller when it refers to a model class, it would look in its 
module then its parent, etc. on to the root (no) module
* the would allow you to define a module with model behavior and then 
include it in both a root level model and maybe some other module, such 
that you could cherry pick models to override and put in a module directory 
that could have slight changes in the module version of the model.
* by changing the standard serialization to just look at mass assignment 
attributes and associations to define what is 
serializable/deserializable/persistable with a few additions, you could 
have different views and not even have to define which models you are using 
in the controller, because the module would define those
* this could get rid of the need for strong_parameters, 
activemodel:serializers, etc. to some extent similar to Roar, but using 
existing models in a very DRY way

Anyway. Instead of this, I''m trying out roar-rails, and am in-process
of
creating default representers so that representers are only needed when the 
user doesn''t want to use what they''ve defined via mass
assignment security,
etc.

The only problem so far is that I had functionality to allow the user to 
specify some fields to be serialized into json (or limit them) via the 
request itself. That worked before when I was using as_json directly, but 
now to do that I would have to create new representer classes each time, 
which is not good because they would need to be new classes, and I was 
going to dup a default representer, change the name and use that, but that 
would build up classes that wouldn''t go away. Will figure it out
though...

This is under development/may change/go away later and untested, but: 
https://github.com/garysweaver/restful_json/blob/3.0.0/lib/restful_json/roar/entity_representer.rb

Right now there is no difference between default entity and collection 
representer. The reason I''m using roar/roar-rails vs. something else is
to
try to both persist JSON and (de)serialize json and support different views 
of the same model in a DRY way.

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Gary Weaver

2012-Sep-13 22:22 UTC

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Re: Wierdness with dependency resolution with models in modules

One last thing on the topic of constant resolution: if anyone sees a big 
problem with what I do in this gem, let me know:
https://github.com/garysweaver/classmeta

I don''t think I''m going to go down the road of using it, but
maybe if I
stripped out the transformer stuff that I''m not sure anyone would use,
they
could just use it to dup and rename classes in a way that works with Rails 
caching and autoloading.

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Gary Weaver

2012-Sep-14 12:53 UTC

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Re: Wierdness with dependency resolution with models in modules

On Thursday, September 13, 2012 6:19:03 PM UTC-4, Gary Weaver
wrote:>
> This is under development/may change/go away later and untested, but: 
>
https://github.com/garysweaver/restful_json/blob/3.0.0/lib/restful_json/roar/entity_representer.rb
>
BTW- this is not the suggested way to do things in roar/roar-rails; 
mirroring the associations and attributes in the representer wouldn''t
work
in roar 0.11.3 
<https://github.com/apotonick/roar/commit/a2f954e0d3cfa7ed99b33e3b416ac868358a4f7e>because
there is no guarding against circular references since it doesn''t
intend to
be used like this, but I''m talking with Nick about it to see if there
is a
workaround. Ok, will stop going off on a tangent now...

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Rails core - Sep 2012 - Wierdness with dependency resolution with models in modules

Wierdness with dependency resolution with models in modules

Re: Wierdness with dependency resolution with models in modules

Re: Wierdness with dependency resolution with models in modules

Re: Wierdness with dependency resolution with models in modules

Re: Wierdness with dependency resolution with models in modules

Re: Wierdness with dependency resolution with models in modules

Re: Wierdness with dependency resolution with models in modules

Re: Wierdness with dependency resolution with models in modules

Re: Wierdness with dependency resolution with models in modules