了解 Rails 控制器 - 通过关联模型的实例变量查看连接
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【中文标题】了解 Rails 控制器 - 通过关联模型的实例变量查看连接【英文标题】：Understanding Rails controller - view connection via instance variable of associated model 【发布时间】：2015-05-31 01:29:38 【问题描述】：我是一个新手，试图了解如何正确使用控制器中关联模型的实例变量以使它们可用于视图。这是如何运作的？有标准吗？我不断收到未定义的方法错误。 @example = Example.find(params[:id]) 或 @example = Example.find(example_params) 的正确用法是什么？对于相关模型？每个控制器操作是否具有特定的 @instance 变量公式（即 Example.all 用于 index ）？ 有谁知道关于控制器视图使用实例变量的综合指南？
代码
型号
class Presupuesto < ActiveRecord::Base
belongs_to :cliente
has_many :ordenes, dependent: :destroy
has_many :medios, :through => :ordenes
has_one :factura
validates :fecha, :titulo, :cliente_id, :producto, presence: true
end
class Factura < ActiveRecord::Base
has_many :factura_items
belongs_to :cliente
belongs_to :presupuesto
validates :fecha_de_expedicion, presence: true
end
查看
_form.html.erb
<% content_for :title do %>Factura<% end %>
<h3>Factura</h3>
<div class="form">
<%= simple_form_for @factura do |form| %>
<%= form.error_notification %>
<%= form.input :fecha_de_expedicion %>
<%= form.association :cliente, :label_method => :nombre, label: "Cliente", :include_blank => false %>
<%= form.association :presupuesto, :label_method => :titulo, label: "Presupuesto", :include_blank => false %>
<%= form.button :submit, 'Submit', class: 'submit' %>
<% end %>
</div>
new.html.erb
<h1>New Factura</h1>
<%= render 'form' %>
<%= link_to 'Back', facturas_path %>
控制器
class FacturasController < ApplicationController
# GET /facturas
# GET /facturas.json
def index
@factura = Factura.all
@cliente = Cliente.all
end
# GET /facturas/1
# GET /facturas/1.json
def show
@factura = Factura.find(params[:id])
@cliente = @factura.cliente
@presupuesto = @factura.presupuesto
end
# GET /facturas/new
def new
@factura = Factura.new
@presupuesto = Presupuesto.all
#@ordenes = Ordene.where(aprobado_por_cliente: 1)
end
# GET /facturas/1/edit
def edit
end
# POST /facturas
# POST /facturas.json
def create
@factura = Factura.new(factura_params)
respond_to do |format|
if @factura.save
format.html redirect_to @factura, notice: 'Factura was successfully created.'
format.json render :show, status: :created, location: @factura
else
format.html render :new
format.json render json: @factura.errors, status: :unprocessable_entity
end
end`
end
# PATCH/PUT /facturas/1
# PATCH/PUT /facturas/1.json
def update
respond_to do |format|
if @factura.update(factura_params)
format.html redirect_to @factura, notice: 'Factura was successfully updated.'
format.json render :show, status: :ok, location: @factura
else
format.html render :edit
format.json render json: @factura.errors, status: :unprocessable_entity
end
end
end
# DELETE /facturas/1
# DELETE /facturas/1.json
def destroy
@factura.destroy
respond_to do |format|
format.html redirect_to facturas_url, notice: 'Factura was successfully destroyed.'
format.json head :no_content
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_factura
@factura = Factura.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def factura_params
params.require(:factura).permit(:fecha_de_expedicion, :cliente_id, :presupuesto_id )
end
end
错误 /facturas/new 处的 NoMethodError #
的未定义方法“presupuesto_id”Started GET "/facturas/new" for ::1 at 2015-05-30 21:06:26 -0500
Processing by FacturasController#new as HTML
Cliente Load (0.2ms) SELECT "clientes".* FROM "clientes"
Presupuesto Load (0.1ms) SELECT "presupuestos".* FROM "presupuestos"
Rendered facturas/_form.html.erb (21.1ms)
Rendered facturas/new.html.erb within layouts/application (22.6ms)
Completed 500 Internal Server Error in 29ms
NoMethodError - undefined method `presupuesto_id' for #<Factura:0x007feadf9dc930>:
activemodel (4.2.0) lib/active_model/attribute_methods.rb:433:in `method_missing'
actionview (4.2.0) lib/action_view/helpers/tags/base.rb:28:in `value'
actionview (4.2.0) lib/action_view/helpers/tags/collection_select.rb:16:in `block in render'
actionview (4.2.0) lib/action_view/helpers/tags/collection_select.rb:16:in `render'
actionview (4.2.0) lib/action_view/helpers/form_options_helper.rb:202:in `collection_select'
actionview (4.2.0) lib/action_view/helpers/form_options_helper.rb:789:in `collection_select'
simple_form (3.1.0) lib/simple_form/inputs/collection_select_input.rb:9:in `input'
simple_form (3.1.0) lib/simple_form/wrappers/leaf.rb:19:in `render'
simple_form (3.1.0) lib/simple_form/wrappers/many.rb:28:in `block in render'
simple_form (3.1.0) lib/simple_form/wrappers/many.rb:26:in `render'
simple_form (3.1.0) lib/simple_form/wrappers/root.rb:15:in `render'
simple_form (3.1.0) lib/simple_form/form_builder.rb:115:in `input'
simple_form (3.1.0) lib/simple_form/form_builder.rb:191:in `association'
app/views/facturas/_form.html.erb:8:in `block in _app_views_facturas__form_html_erb___1959803079335200881_70323378590380'
actionview (4.2.0) lib/action_view/helpers/capture_helper.rb:38:in `block in capture'
actionview (4.2.0) lib/action_view/helpers/capture_helper.rb:200:in `with_output_buffer'
actionview (4.2.0) lib/action_view/helpers/capture_helper.rb:38:in `capture'
actionview (4.2.0) lib/action_view/helpers/form_helper.rb:444:in `form_for'
simple_form (3.1.0) lib/simple_form/action_view_extensions/form_helper.rb:26:in `block in simple_form_for'
simple_form (3.1.0) lib/simple_form/action_view_extensions/form_helper.rb:45:in `with_simple_form_field_error_proc'
simple_form (3.1.0) lib/simple_form/action_view_extensions/form_helper.rb:25:in `simple_form_for'
app/views/facturas/_form.html.erb:4:in `_app_views_facturas__form_html_erb___1959803079335200881_70323378590380'
actionview (4.2.0) lib/action_view/template.rb:145:in `block in render'
activesupport (4.2.0) lib/active_support/notifications.rb:166:in `instrument'
actionview (4.2.0) lib/action_view/template.rb:333:in `instrument'
actionview (4.2.0) lib/action_view/template.rb:143:in `render'
actionview (4.2.0) lib/action_view/renderer/partial_renderer.rb:339:in `render_partial'
actionview (4.2.0) lib/action_view/renderer/partial_renderer.rb:310:in `block in render'
actionview (4.2.0) lib/action_view/renderer/abstract_renderer.rb:39:in `block in instrument'
activesupport (4.2.0) lib/active_support/notifications.rb:164:in `block in instrument'
activesupport (4.2.0) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.2.0) lib/active_support/notifications.rb:164:in `instrument'
actionview (4.2.0) lib/action_view/renderer/abstract_renderer.rb:39:in `instrument'
actionview (4.2.0) lib/action_view/renderer/partial_renderer.rb:309:in `render'
actionview (4.2.0) lib/action_view/renderer/renderer.rb:47:in `render_partial'
actionview (4.2.0) lib/action_view/helpers/rendering_helper.rb:35:in `render'
app/views/facturas/new.html.erb:3:in `_app_views_facturas_new_html_erb___1900732511694118275_70323400237940'
actionview (4.2.0) lib/action_view/template.rb:145:in `block in render'
activesupport (4.2.0) lib/active_support
:in `instrument'
actionview (4.2.0) lib/action_view/template.rb:333:in `instrument'
actionview (4.2.0) lib/action_view/template.rb:143:in `render'
actionview (4.2.0) lib/action_view/renderer/template_renderer.rb:54:in `block (2 levels) in render_template'
actionview (4.2.0) lib/action_view/renderer/abstract_renderer.rb:39:in `block in instrument'
activesupport (4.2.0) lib/active_support/notifications.rb:164:in `block in instrument'
activesupport (4.2.0) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.2.0) lib/active_support/notifications.rb:164:in `instrument'
actionview (4.2.0) lib/action_view/renderer/abstract_renderer.rb:39:in `instrument'
actionview (4.2.0) lib/action_view/renderer/template_renderer.rb:53:in `block in render_template'
actionview (4.2.0) lib/action_view/renderer/template_renderer.rb:61:in `render_with_layout'
actionview (4.2.0) lib/action_view/renderer/template_renderer.rb:52:in `render_template'
actionview (4.2.0) lib/action_view/renderer/template_renderer.rb:14:in `render'
actionview (4.2.0) lib/action_view/renderer/renderer.rb:42:in `render_template'
actionview (4.2.0) lib/action_view/renderer/renderer.rb:23:in `render'
actionview (4.2.0) lib/action_view/rendering.rb:100:in `_render_template'
actionpack (4.2.0) lib/action_controller/metal/streaming.rb:217:in `_render_template'
actionview (4.2.0) lib/action_view/rendering.rb:83:in `render_to_body'
actionpack (4.2.0) lib/action_controller/metal/rendering.rb:32:in `render_to_body'
actionpack (4.2.0) lib/action_controller/metal/renderers.rb:37:in `render_to_body'
actionpack (4.2.0) lib/abstract_controller/rendering.rb:25:in `render'
actionpack (4.2.0) lib/action_controller/metal/rendering.rb:16:in `render'
actionpack (4.2.0) lib/action_controller/metal/instrumentation.rb:41:in `block (2 levels) in render'
activesupport (4.2.0) lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
/Users/davefogo/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/benchmark.rb:303:in `realtime'
activesupport (4.2.0) lib/active_support/core_ext/benchmark.rb:12:in `ms'
actionpack (4.2.0) lib/action_controller/metal/instrumentation.rb:41:in `block in render'
actionpack (4.2.0) lib/action_controller/metal/instrumentation.rb:84:in `cleanup_view_runtime'
activerecord (4.2.0) lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime'
actionpack (4.2.0) lib/action_controller/metal/instrumentation.rb:40:in `render'
action
【问题讨论】：
不清楚你在问什么。在控制器方法中定义的任何实例变量都将在该方法呈现的视图中可用。请发布您正在使用的实际代码以及您收到的任何错误消息的完整文本。 如果您需要其他内容，请告诉我。我真的很困惑如何使代码通过。 【参考方案1】：您的视图中似乎有一个未定义的方法#presupuesto_id，特别是在 app/views/facturas/_form.html.erb 第 8 行中。这可能需要在控制器底部注释掉所需的参数文件或您试图在错误的对象（@factura）上调用方法（presupuesto_id）。查看两个呈现的视图以查看对象是如何传递的也很有帮助，即_form.html.erb和new.html.erb。
这篇文章很好地解释了控制器/视图的关系以及每个动作中的实例变量的解释。 http://www.sitepoint.com/building-your-first-rails-application-views-and-controllers/
尝试更改表单以查找 presupuesto 的 id 而不是标题。如果可行，那么您需要向 Factura 模型添加一个新方法或范围，该模型将找到名称为“title”的 presupuesto，并将其分配给新创建的 Factura 实例。
<%= form.association :cliente, :label_method => :nombre, label: "Cliente", :include_blank => false %>
<%= form.association :presupuesto, :label_method => :nombre, label: "Presupuesto", :include_blank => false %>
【讨论】：
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