NoMethodError: undefined method `one' for #<Hanami::Model::Associations::HasMany>

[checkbutton]

The following example returns a NoMethodError: undefined method 'one' for #<Hanami::Model::Associations::HasMany>:

class AuthorRepository < Hanami::Repository
  associations do
    has_many :books
  end

  def find_book(author, id)
    book_for(author, id).one
  end

  private

  def book_for(author, id)
    assoc(:books, author).where(id: id)
  end
end

Tested it on Hanami 1.3.1, according to this documentation:
https://guides.hanamirb.org/associations/has-many/#querying
It seems that it is also wrongly documented.

[landongrindheim]

I've dug into this a little and would like to pitch in to resolve it 😄

There are a couple of ways this can be addressed, depending on whether #one is considered an appropriate method for HasMany.

If it shouldn't be supported, I can remove it from the docs. I noticed the code in the docs is also in place in the Hanami/Model repository.

Given this block of code...

  def book_for(author, id)
    assoc(:books, author).where(id: id)
  end

... it seems reasonable to assume that there will be one book (since scoping is done on an id). However, if this scoping was done on a non-unique column/attribute, relying on ROM's one method would easily result in a TupleCountMismatchError. Perhaps a #first approach would be better suited to this problem?

[jodosha]

@mereghost Would you please have a look? Thanks.

[landongrindheim]

I'll provide two solutions to this. One adds the method #one to HasMany (#553), the other removes the documentation from this repository as well as the guides repository (#554) 🙂

[landongrindheim]

@jodosha @mereghost Any thoughts on the solutions referenced above?