has_many构建方法,Rails

Question

另一个新手问题.

目标:每种成分可以有零个或多个单位转换.我想在显示特定成分的页面上创建一个新的单位转换链接.我无法让它发挥作用.

成分模型:

class Ingredient < ActiveRecord::Base
   belongs_to :unit
   has_many :unit_conversion
end

单位换算模型:

class UnitConversion < ActiveRecord::Base
  belongs_to :Ingredient
end

单位转换控制器(新)

def new
    @ingredient = Ingredient.all
    @unit_conversion = @ingredient.unit_conversions.build(params[:unit_conversion])
    if @unit_conversion.save then
        redirect_to ingredient_unit_conversion_url(@ingredient, @comment)
        else
            render :action => "new"
        end
  end

相关路线:

  map.resources :ingredients, :has_many => :unit_conversions

显示成分链接:

<%= link_to 'Add Unit Conversion', new_ingredient_unit_conversion_path(@ingredient) %>

这是错误:

 NoMethodError in Unit conversionsController#new

undefined method `unit_conversions' for #<Array:0x3fdf920>

RAILS_ROOT: C:/Users/joan/dh
Application Trace | Framework Trace | Full Trace

C:/Users/joan/dh/app/controllers/unit_conversions_controller.rb:14:in `new'

救命!我对这一切都很不满.

Answer 1

单位转换控制器new,create应该是:

def new
  @ingredient = Ingredient.find(params[:ingredient_id])    
  @unit_conversion = @ingredient.unit_conversions.build
end

def create
  @ingredient = Ingredient.find(params[:ingredient_id])    
  @unit_conversion = @ingredient.unit_conversions.build(params[:unit_conversion])

  if @unit_conversion.save
    flash[:notice] = "Successfully created unit conversion."
    redirect_to ingredient_unit_conversions_url(@ingredient)
  else
    render :action => 'new'
  end
end

此外,此截屏视频是嵌套资源的一个很好的资源.

Answer 2

has_many :unit_conversion

因为你用它来调用它应该是复数

@unit_conversion = @ingredient.unit_conversions.build

你的控制器

def new
  @ingredient = Ingredient.all

应该打电话#new来设置一个新的成分或#find抓住现有的成分.

@ingredient = Ingredient.new       # returns a new Ingredient

要么

@ingredient = Ingredient.find(...) # returns an existing Ingredient

您选择哪一个符合您的要求.

另外,这是一个错字,对吧？

belongs_to :Ingredient

你可能想要小写 :ingredient