Rails Associations: Going from has_many to has_one

Question

I'm still new to Rails and am try to figure out how to associate a model with a user as a has_one.

This was set up initially assuming that my users would have many finances. Now, I need to change it so a user has one finance.

Finance model :

class Finance < ActiveRecord::Base
    belongs_to :user
    validates :age, presence: true
    validates :zip, presence: true
end

User model :

class User < ActiveRecord::Base
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  has_many :finances
end

When I change has_many :finances to has_one :finances, my finances controller is throwing an error.

class FinancesController < ApplicationController    
  # GET /finances
  # GET /finances.json
  def index
    @finances = Finance.find_all_by_user_id current_user[:id] if current_user
  end

  # GET /finances/new
  def new
    @finance = current_user.finances.build
  end

  # GET /finances/1/edit
  def edit
  end

  # POST /finances
  # POST /finances.json
  def create
    @finance = current_user.finances.build(finance_params)

    respond_to do |format|
      if @finance.save
        format.html { redirect_to @finance, notice: 'Successfully created.' }
        format.json { render action: 'show', status: :created, location: @finance }
      else
        format.html { render action: 'new' }
        format.json { render json: @finance.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /finances/1
  # PATCH/PUT /finances/1.json
  def update
    respond_to do |format|
      if @finance.update(finance_params)
        format.html { redirect_to @finance, notice: 'Successfully updated.' }
        format.json { head :no_content }
      else
        format.html { render action: 'edit' }
        format.json { render json: @finance.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /finances/1
  # DELETE /finances/1.json
  def destroy
    @finance.destroy
    respond_to do |format|
      format.html { redirect_to finances_url }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_finance
      @finance = Finance.find(params[:id])
    end

    def correct_user
        @finance = current_user.finances.find_by(id: params[:id])
        redirect_to root_path, notice: "Welcome to TrustRose" if @finance.nil?
    end
end

The error comes here:

 @finance = current_user.finances.find_by(id: params[:id])

I believe this will need to change, but I am not how to query the database to find the finance associated with the user now that the user only has one.

Answer 1

You problem relates to Active Record Pluralisation of your model names: http://guides.rubyonrails.org/association_basics.html

Try this:

@finance = current_user.finance

Answer 2

In your routes.rb , change resources :finances to resource :finance

Then, change your User model

class User < ActiveRecord::Base
  ...

  has_one :finance
end

With the has_one association, you can use @finance = current_user.finance in your controller

Now, display it in your view using something like:

<%= @finance.age %>

Hope that helps?