CODEWITHSUNDEEP
ruby-on-railsruby
Andrey Deineko
Andrey Deineko

Reputation: 52347

module and class with the same name in Rails project

Earlier today I had this problem, when I was running

sidekiq

I was getting the following error:

I, [2015-09-04T12:43:33.723243 #15197]  INFO -- : Celluloid 0.17.1.2 is running in BACKPORTED mode. [ http://git.io/vJf3J ]
Report is not a class
/home/andreydeineko/employees/app/models/report.rb:1:in `<top (required)>'

but Report was AR class/model without any typos.

It occurred the error was due to the fact, that in the project there was previously defined module called Report.

Why is this problem with same class and module name occurred?

Is there any Ruby/Rails convention to not name the class and module with same name?

Upvotes: 0

Views: 4497

Answers (2)

Stefan
Stefan

Reputation: 114138

Is there any Ruby/Rails convention to not name the class and module with same name?

The class keyword does two things - it either create a new class and assigns it to the given constant or it reopens an existing class based on the given constant. (same for module)

In the latter case, it will also raise an error if the constant is not the expected class. It does not matter whether it is a module or another object:

Report = 123

class Report
end
#=> TypeError: Report is not a class

Upvotes: 1

Simone Carletti
Simone Carletti

Reputation: 176352

You cannot reuse the same name for a Class and a Module. Internally, in Ruby modules are represented as class structures therefore they share the same object space.

Moreover, when you define a Module/Class, you can access the name as a constant.

class Report
  def foo
    p "report"
  end
end

Report
=> Report

defined? Report
 => "constant"

in fact, you can also write

Report = Class.new do
  def foo
    p "report"
  end
end

report = Report.new
report.foo

Long story short, if you define Report as Class, you cannot create a Module with the same name.

Upvotes: 3

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