Update the create action as below:
def create
...
respond_to do |format|
if @reservation.save
format.html do
redirect_to '/'
end
format.json { render json: @reservation.to_json }
else
format.html { render 'new'} ## Specify the format in which you are rendering "new" page
format.json { render json: @reservation.errors } ## You might want to specify a json format as well
end
end
end
You are using respond_to method but anot specifying the format in which a new page is rendered. Hence, the error ActionController::UnknownFormat .