Sorbet asking a `sig` for `attr_reader`

user_5865743 0
Viewed 1327

Sorbet is showing an error for the attr_reader, but correct me if I am wrong, sigs are required when the function is declared, not called, right?

I have tried going through the documentation but all I got is this note

Note: Many Ruby constructs that look like local variables are actually method calls without parens! Specifically, watch out for attr_reader and zero-argument method definitions.

app/util/hodor.rb:125: This function does not have a `sig` https://sorbet.org/docs/error-reference#7017
     125 |  attr_reader(:collection_name)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
sorbet ruby
3 Answers

The error does not have to do with the attr_reader method itself needing a sig, but with :collection_name. The signature for attr_reader is already known, but the new method it dynamically creates, #collection_name does not have a known sig, and Sorbet expects this to be the place where you give it one.

You can do this to fix it:

sig { returns(String) }
attr_reader(:collection_name)
user_19567210

attr_reader(attribute) is the equivalent of :

def attribute
  @attribute
end

This is probably why Sorbet is asking for a sig.

user_116597630

Here's the Sorbet documentation on it:

It goes something like this:

# typed: true
class A
  extend T::Sig

  sig {returns(Integer)}
  attr_reader :reader

  sig {params(writer: Integer).returns(Integer)}
  attr_writer :writer

  # For attr_accessor, write the sig for the reader portion.
  # (Sorbet will use that to write the sig for the writer portion.)
  sig {returns(Integer)}
  attr_accessor :accessor

  sig {void}
  def initialize
    @reader = T.let(0, Integer)
    @writer = T.let(0, Integer)
    @accessor = T.let(0, Integer)
  end
end
Rimian_638100
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