使用Ruby On Rails添加數字並保存到數據庫

Question

對於RoR而言，我很新，並且在試驗某些語法方面還很困難。

我不知道如何添加兩個輸入的號碼從這裏來的：

<div class="field"> 
<%= f.label :point1 %><br> 
<%= f.number_field :point1 %> 

</div> 
<div class="field"> 
<%= f.label :point2 %><br> 
<%= f.number_field :point2 %> 

</div> 

我也想將號碼保存到數據庫，包括它們的總和。 我已經從互聯網上搜索過它，但對結果並不滿意。

我希望有人能幫助我。謝謝。

順便說一句，我知道如何將兩個輸入的數字保存在數據庫中，除了總和。

這些是我的代碼！

player.rb

class Player < ActiveRecord::Base 
    before_save :add_point1_and_point2 
private 
def add_point1_and_point2 
    self.point3 = self.point1 + self.point2 
    self.save 
end 
end 

_form.html.erb

<%= form_for(@player) do |f| %> 
    <% if @player.errors.any? %> 
    <div id="error_explanation"> 
     <h2><%= pluralize(@player.errors.count, "error") %> prohibited this player from being saved:</h2> 

     <ul> 
     <% @player.errors.full_messages.each do |message| %> 
     <li><%= message %></li> 
     <% end %> 
     </ul> 
    </div> 
    <% end %> 

<% sum = 0 %> 
    <div class="field"> 
    <%= f.label :point1 %><br> 
    <%= f.number_field :point1 %> 

    </div> 
    <div class="field"> 
    <%= f.label :point2 %><br> 
    <%= f.number_field :point2 %> 

    </div> 


    </div> 
    <div class="actions"> 
    <%= f.submit %> 

    </div> 
<% end %> 

players_controller.rb

class PlayersController < ApplicationController 

    before_action :set_player, only: [:show, :edit, :update, :destroy] 

    # GET /players 
    # GET /players.json 
    def index 
    @players = Player.all 
    end 

    # GET /players/1 
    # GET /players/1.json 
    def show 
    end 

    # GET /players/new 
    def new 
    @player = Player.new 
    end 




    # GET /players/1/edit 
    def edit 
    end 

    # POST /players 
    # POST /players.json 
    def create 

    # @player = Player.new(sum_num :point3) 

    @player = Player.new(player_params) 

    respond_to do |format| 
     if @player.save 

     format.html { redirect_to @player, notice: 'Player was successfully created.' } 
     format.json { render :show, status: :created, location: @player } 
     else 
     format.html { render :new } 
     format.json { render json: @player.errors, status: :unprocessable_entity } 
     end 
    end 
    end 

    # PATCH/PUT /players/1 
    # PATCH/PUT /players/1.json 
    def update 
    respond_to do |format| 
     if @player.update(player_params) 
     format.html { redirect_to @player, notice: 'Player was successfully updated.' } 
     format.json { render :show, status: :ok, location: @player } 
     else 
     format.html { render :edit } 
     format.json { render json: @player.errors, status: :unprocessable_entity } 
     end 
    end 
    end 

    # DELETE /players/1 
    # DELETE /players/1.json 
    def destroy 
    @player.destroy 
    respond_to do |format| 
     format.html { redirect_to players_url, notice: 'Player was successfully destroyed.' } 
     format.json { head :no_content } 
    end 
    end 



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

    # Never trust parameters from the scary internet, only allow the white list through. 
    def player_params 
     params.require(:player).permit(:point1, :point2) 
    end 

end 

Answer 1

檢查ActiveRecord Callbacks。尋找before_save和after_save

在你model，你應該有類似這樣的

before_save :add_point1_and_point2 
private 
def add_point1_and_point2 
    sum_value = self.point1 + self.point2 
    self.assign_attributes(sum_column: sum_value) 
end 

Answer 2

代碼那麼有幾種方式做到這一點。但是你不能在before_save或after_save這裏使用self.save，因爲保存會再次調用這些before_save和after_save，因此堆棧級別太深。使用update_column相反，它不會引發任何回調

after_save :add_point1_and_point2 
def add_point1_and_point2 
    update_column(:point3, point1 + point2) 
end 

Answer 3

1日的事情：你缺少你的結果列可能是列「和」

＃這將在新列總和添加到播放器。

rails g migration add_sum_to_players sum:integer 
rake db:migrate 

下一個試試這個模型中的文件：

#player.rb 
class Player < ActiveRecord::Base 

before_save :calculate_sum 

private 
    def calculate_sum 
    result = point1 + point2 
    self.assign_attributes(sum: result) 
    end 
end 

由於我們剛剛分配的屬性（和作爲點1和點2的+），所以這不是要救它。這只是分配，因爲我們正在觸發before_save。 因此，當保存將被觸發時，這個總和值將被自動保存。 :)