undefined method {....}_url when calling create in api controller

undefined method {....}_url when calling create in api controller

I'm working on a rails app that serves some json and I'm having hard time
understanding what is going on in the code below (simplified for the
purpose of understanding the issue).
module Api
class ProjectController < ApplicationController
respond_to :json
def show
x = {"id"=>17, "name"=>"abc", "version"=>1}
respond_with x.to_json, status: 200
end
def create
x = {"id"=>17, "name"=>"abc", "version"=>1}
respond_with x.to_json, status: 200
end
end
end
The show action works fine but when I call the create action I get
NoMethodError (undefined method '{"id":17,"name":"abc","version":1}_url'
for Api::ProjectsController:0x007fbb2294cd18)
Why do I get this error while show works just fine? is it because create
makes a post instead of a get?
How can I solve it?
Thanks for your help and have a nice day.