One-to-One: Undefined method build

Question

got a problem with one to one relations

I have some Matches and i want to have one score for a match.

my Match.rb

has_one :score, :dependent          


        

Answer 1

You should be doing match.build_score. This is because when you call the score method it would attempt to fetch the association, and because it's not defined yet, it will return nil. Then you call build on nil and that's why it blows up.

has_many association methods return a sort of "proxy" object to the objects returned by calls to them, so this is why things like posts.comments.build works. The methods for belongs_to and has_one associations attempt to fetch the associations straight off, and so you need to do build_association rather than association.build.

Answer 2

You can create a score by using the below example

@match.build_score
or
@match.create_score

Answer 3

Use build instead of new:

def new
    @match = Match.find(params[:match_id])
    @score = @match.build_score
end

Here are the docs for this: http://guides.rubyonrails.org/association_basics.html#belongs_to-build_association

Similarly, in the create method, do it like this:

def create
    @match = Match.find(params[:match_id])
    @score = @match.create_score(params[:score])
end

Docs for this: http://guides.rubyonrails.org/association_basics.html#belongs_to-create_association