Question

不确定原因，但是当我将这个新行添加到我的团队视图中时，我将未定义的方法“空”？错误

<div class="field">
  <%= f.label :field_id %><br>
  <%= f.select :field_id, @fields, prompt: "select a field" %>
</div>

以下是团队和领域的模型

class Team < ActiveRecord::Base
  has_many :users
  belongs_to :field
end

class Field < ActiveRecord::Base
  has_many :teams
end

我必须将field_id迁移到team表中，这是

class AddFieldIdToTeams < ActiveRecord::Migration
  def change
    add_column :teams, :field_id, :integer
  end
end

截至目前，我可以访问localhost：3000 / fields并创建一个包含名称和位置设置的新字段。当我去localhost：3000 / teams / new时发生错误。我正在尝试获取字段的下拉菜单，这样当您创建团队时，它将与团队将要播放的字段相关联。如果需要更多信息，请告诉我。感谢

编辑添加我的字段控制器

class FieldsController < ApplicationController
  before_action :set_field, only: [:show, :edit, :update, :destroy]

  # GET /fields
  # GET /fields.json
  def index
    @fields = Field.all
  end

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

  # GET /fields/new
  def new
    @field = Field.new
  end

  # GET /fields/1/edit
  def edit
  end

  # POST /fields
  # POST /fields.json
  def create
    @field = Field.new(field_params)

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

  # PATCH/PUT /fields/1
  # PATCH/PUT /fields/1.json
  def update
    respond_to do |format|
      if @field.update(field_params)
        format.html { redirect_to @field, notice: 'Field was successfully updated.' }
        format.json { head :no_content }
      else
        format.html { render action: 'edit' }
        format.json { render json: @field.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /fields/1
  # DELETE /fields/1.json
  def destroy
    @field.destroy
    respond_to do |format|
      format.html { redirect_to fields_url }
      format.json { head :no_content }
    end
  end

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

    # Never trust parameters from the scary internet, only allow the white list through.
    def field_params
      params.require(:field).permit(:name, :location)
    end
end

Answer 1

@fields应该在你的控制器中

@fields = Field.all

表格

<%= f.select :field_id, options_from_collection_for_select(@fields, "id", "name"),
:prompt => "Select field" %>

将“name”替换为您希望用户在下拉菜单中选择值时看到的字段模型中的值

替代方案可能是这不需要@fields变量。

<%= f.select :field_id, Field.find(:all).collect {|f| [ "#{f.name}", f.id ] }  %>

再次改变f.name，就像我之前的例子一样

Answer 2

您没有在团队控制器的新操作中设置@fields变量

未定义的方法`空？' for nil：添加新字段表单时为NilClass

2 个答案: