CODEWITHSUNDEEP
ruby
rizkyduut
rizkyduut

Reputation: 23

Superclass mismatch for class in Ruby

I'm working on project that requires different classes to have the same name like this:

lib/command.rb

class Command
end

lib/command/group.rb

class Command
  class Group < Command
  end
end

lib/command/group/add.rb

class Command
  class Group
    class Add < Group
      # do something
    end
  end
end

and lib/group.rb

class Group
  # do something
end

Rakefile

task :reload do
  Dir[File.dirname(__FILE__) + '/lib/**/*.rb'].each{ |file| load file }
end

task default: 'reload'

The first three classes behaves like a helper, and last class is the model.

When I run Rakefile to load all classes, it will raise the TypeError: superclass mismatch for class Group indeed.

How should I solve it without renaming one of the Group classes? Is it possible?

Upvotes: 1

Views: 7469

Answers (2)

ndnenkov
ndnenkov

Reputation: 36101

lib/command/group/add.rb may get loaded before lib/command/group.rb. Hence in the latter, it appears as if you try to change which class Group inherits from.

The band aid solution would be to point to the same subclass in all files. Aka in lib/command/group/add.rb, you should add < Command.

The real solution should be to never use a class/module for namespacing and attach functionality to it.

This issue was raised in Euruko 2016 and Matz said they might consider a special keyword for it. [Citation needed]

Upvotes: 3

tombeynon
tombeynon

Reputation: 2346

Thanks for providing further code. It's now clear that there is an error here. You define Command::Group twice, but only one of them inherits from Command

lib/command/group.rb

class Command
  class Group < Command
  end
end

lib/command/group/add.rb

class Command
  class Group # missing inheritance
    class Add < Group
      # do something
    end
  end
end

Upvotes: 2

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