ruby-on-rails - 是否有任何功能可以在 Ruby on Rails 中创建模型/表列名称的自动值？

Question

我正在使用 Postgresql 设置新的简单 ruby​​ on rails 博客 api，它必须包含 2 个部分。第一部分是为 CRUD 创建简单的博客。它已经准备好了。第二部分是三角形检查器......我添加了简单的三角形 MVC 文件，它有 4 个模型属性 > name,edge1,edge2,edge3......现在我的程序必须分配三角形名称 Scalene/等边/自动等腰。例如，用户输入 edge1=edge2=edge3=4 并且名称必须自动为“Equilatera”...并且我必须将边长添加到 URL 地址...例如:http://localhost:3000/triangles/2/a=3,b=3,c=3,'等距'

有没有简单的解决办法或者方法或者功能或者推荐？所有文件都在这里: https://github.com/SuperSayiyajin/My_Ruby_Codes

谢谢...

• 我试图修改 triangle.rb 类文件，但是当我创建 initialize(edge1,edge2,edge3) 方法时，来自 triangle-controller 的新方法给我的参数错误给定 1 expected 3...

• 我尝试向 Controller 添加一些 if 语句 block 并查看 rb 文件，但我失败了。它不起作用。

• 我尝试为数据库迁移创建 Postgresql 触发器，但它给了我BEGIN 仅在顶层错误时允许。

• 我的三角模型

    class Triangle < ApplicationRecord
      validates :edge1, presence: true
      validates :edge2, presence: true
      validates :edge3, presence: true
    
      def triangle(a, b, c)
        t = Triangle.new(a, b, c)
        return t.type
      end
    
      def initialize(a, b, c)
        @edge1 = a
        @edge2 = b
        @edge3 = c
        @sides = [a,b,c].sort
        ValidLength
      end
    
      def type
        case @sides.uniq.size
        when 1 then :equilateral
        when 2 then :isosceles
        else :scalene
        end
      end
    
      private
      def ValidLength
        if @sides.any? { |x| x <= 0 }
          raise TriangleError, "Sides must be greater than 0"
        end
    
        if @sides[0] + @sides[1] <= @sides[2]
          raise TriangleError, "Not valid triangle lengths"    
        end
      end
    end

-我的三角形模型错误 https://imge.to/i/51ydR

• 我的 Postgresql 触发器代码。我在 db/migration 中创建，当我运行 rake db:migrate:up VERSION=my_migration_name.rb >> 它给了我 BEGIN is permitted only at toplevel 错误。

    def change
    CREATE TRIGGER triangles_name_insert AFTER INSERT ON triangles
    FOR EACH ROW
    BEGIN
        if edge1 + edge2 < edge3
          UPDATE triangles SET name = 'Invalid Edges';
        else
          if edge1=edge2 and edge1=edge3
            UPDATE triangles SET name = 'Equilateral' ;
          elsif edge1=edge or edge1=edge3 or edge2=edge3
            UPDATE triangles SET name = 'Isosceles' ;
          else
            UPDATE triangles SET name = 'Scalane' ;
          end
        end
    END;
    
    CREATE TRIGGER account_users_after_update_on_name_row_tr AFTER UPDATE ON account_users
    FOR EACH ROW
    BEGIN
        if edge1 + edge2 < edge3
          UPDATE triangles SET name = 'Invalid Edges';
        else
          if edge1=edge2 and edge1=edge3
            UPDATE triangles SET name = 'Equilateral' ;
          elsif edge1=edge or edge1=edge3 or edge2=edge3
            UPDATE triangles SET name = 'Isosceles' ;
          else
            UPDATE triangles SET name = 'Scalane' ;
          end
        end
    END;
      end

-我的 Postgresql 数据库:迁移错误 https://imge.to/i/51MXk

-我的三角 Controller

class TrianglesController < ApplicationController
  before_action :set_triangle, only: [:show, :edit, :update, :destroy]

  # GET /triangles
  # GET /triangles.json
  def index
    @triangles = Triangle.all
  end

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

  # GET /triangles/new
  def new
    @triangle = Triangle.new
  end

  # GET /triangles/1/edit
  def edit
  end

  # POST /triangles
  # POST /triangles.json
  def create
    @triangle = Triangle.new(triangle_params)
    note=" "
    respond_to do |format|
      if @triangle.save
          if [triangle_params].uniq.size == 1
            note='Triangle was successfully created.And it is equilateral'
          elsif [triangle_params].uniq.size == 2
            note='Triangle was successfully created.And it is isosceles'
          else
            note='Triangle was successfully created.And it is scalene'
          end
        format.html { redirect_to @triangle, notice: note}
        #format.json { render :show, status: :created, location: @triangle }
      else
        format.html { render :new }
        #format.json { render json: @triangle.errors, status: :unprocessable_entity }
      end
    end
  end

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

  # DELETE /triangles/1
  # DELETE /triangles/1.json
  def destroy
    @triangle.destroy
    respond_to do |format|
      format.html { redirect_to triangles_url, notice: 'Triangle was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_triangle
      #case [:edge1,:edge2,:edge3].uniq.size
      #when 1 then :equilateral
      #when 2 then :isosceles
      #else        :scalene
      @triangle = Triangle.find(params[:id])
    end

    # Never trust parameters from the scary internet, only allow the white list through.
    def triangle_params
      params.require(:triangle).permit(:edge1, :edge2, :edge3)
    end
end

• 我的 index.hmtl.erb 文件

三角形

姓名 边缘 1 边缘2 边缘3 特性
```

Answer 1

我同意 Sergio 的观点，并且在这种情况下也更喜欢使用 before_save 触发器。应该做的工作不多，所以用 ruby 来做就可以了，而不是将这个应用程序逻辑转移到数据库。

无论如何，如果你想坚持使用 Postgres 触发器，那么你可以使用 reversible migration syntax或 old up/down one :

class AddTriangleTriggersMigration < ActiveRecord::Migration[5.0]
  def change
    reversible do |dir|
      # Specify what to do on 'rails db:migrate' (create triggers)
      dir.up do
        execute <<-SQL
          CREATE TRIGGER triangles_name_insert AFTER INSERT ON triangles
          FOR EACH ROW
          BEGIN
              if edge1 + edge2 < edge3
                  UPDATE triangles SET name = 'Invalid Edges';
              else
                  if edge1=edge2 and edge1=edge3
                  UPDATE triangles SET name = 'Equilateral' ;
                  elsif edge1=edge or edge1=edge3 or edge2=edge3
                  UPDATE triangles SET name = 'Isosceles' ;
                  else
                  UPDATE triangles SET name = 'Scalane' ;
                  end
              end
          END;

          CREATE TRIGGER account_users_after_update_on_name_row_tr AFTER UPDATE ON account_users
          FOR EACH ROW
          BEGIN
              if edge1 + edge2 < edge3
                  UPDATE triangles SET name = 'Invalid Edges';
              else
                  if edge1=edge2 and edge1=edge3
                  UPDATE triangles SET name = 'Equilateral' ;
                  elsif edge1=edge or edge1=edge3 or edge2=edge3
                  UPDATE triangles SET name = 'Isosceles' ;
                  else
                  UPDATE triangles SET name = 'Scalane' ;
                  end
              end
          END;
        SQL
      end

      # Specify what to do on 'rails db:rollback' (drop triggers)
      dir.down do
        execute <<-SQL
          DROP TRIGGER triangles_name_insert;
          DROP TRIGGER account_users_after_update_on_name_row_tr;
        SQL
      end
    end
  end
end

我没有检查你的 SQL 触发器的正确​​性，但如果你想用普通 SQL 编写复杂的迁移，那么你应该以这种方式进行，以便它们是可逆的。