我是rails的新手,我一直在尝试获得两个has_many：虽然关系可以解决(而不是像本文
http://blog.flatironschool.com/post/35346328762/why-you-dont-need-has-and-belongs-to-many所解释的那样使用has_and_belongs_to_many),但现在遇到了Postgres错误：
PG::Error: ERROR: column reference "id" is ambiguous
LINE 1: ...on_id" IS NULL AND "components"."id" = 1 ORDER BY id ASC LIM...
^
: SELECT 1 AS one FROM "components" INNER JOIN "collection_components" ON "components"."id" = "collection_components"."component_id" WHERE "collection_components"."collection_id" IS NULL AND "components"."id" = 1 ORDER BY id ASC LIMIT 1
Rendered collections/_form.html.haml (117.0ms)
Rendered collections/new.html.haml within layouts/application (143.5ms)
Completed 500 Internal Server Error in 164ms
ActiveRecord::StatementInvalid - PG::Error: ERROR: column reference "id" is ambiguous
LINE 1: ...on_id" IS NULL AND "components"."id" = 1 ORDER BY id ASC LIM...
^
_form.html.haml
= form_for @collection do |f|
- if @collection.errors.any?
#error_explanation
%h1= "#{pluralize(@collection.errors.count,"error")} prohibited this collection from being saved:"
%ul
- @collection.errors.full_messages.each do |msg|
%li= msg
.field
- Component.all.each do |component|
= label_tag :component_ids,component.id
= check_Box_tag :component_ids,component.id,@collection.components.include?(component),:name => 'collection[component_ids][]'
.field
= f.label :title
= f.text_field :title
.actions
= f.submit 'Save'
collection_component.rb
class CollectionComponent < ActiveRecord::Base attr_accessible :collection_id,:component_id belongs_to :collection belongs_to :component end
collection.rb
class Collection < ActiveRecord::Base
default_scope order('id ASC')
attr_accessible :style_id,:name,:title,:component
#has_and_belongs_to_many :components
has_many :collection_components,:dependent => :destroy
has_many :components,:through => :collection_components
belongs_to :style
validates_presence_of :style
validates_presence_of :title
before_save :create_name
private
def create_name
self.name = title.parameterize
end
end
component.rb
class Component < ActiveRecord::Base
default_scope order('id ASC')
attr_accessible :category_id,:collection,:style
has_many :collection_components,:dependent => :destroy
has_many :collections,:through => :collection_components
has_many :component_styles
has_many :styles,:through => :component_styles
belongs_to :category
validates_presence_of :category
validates_presence_of :title
before_save :create_name
private
def create_name
self.name = title.parameterize
end
end
collection_components表
Column | Type | Modifiers
---------------+-----------------------------+--------------------------------------------------------------------
id | integer | not null default nextval('collection_components_id_seq'::regclass)
collection_id | integer |
component_id | integer |
created_at | timestamp without time zone | not null
updated_at | timestamp without time zone | not null
Indexes:
"collection_components_pkey" PRIMARY KEY,btree (id)
收藏表
Column | Type | Modifiers
------------+-----------------------------+----------------------------------------------------------
id | integer | not null default nextval('collections_id_seq'::regclass)
style_id | integer |
name | character varying(255) |
title | character varying(255) |
created_at | timestamp without time zone | not null
updated_at | timestamp without time zone | not null
Indexes:
"collections_pkey" PRIMARY KEY,btree (id)
组件表
Column | Type | Modifiers
-------------+-----------------------------+---------------------------------------------------------
id | integer | not null default nextval('components_id_seq'::regclass)
name | character varying(255) |
title | character varying(255) |
category_id | integer |
created_at | timestamp without time zone | not null
updated_at | timestamp without time zone | not null
Indexes:
"components_pkey" PRIMARY KEY,btree (id)
解决方法
试试这个：
default_scope { order('collections.id ASC') } //collection.rb
default_scope { order('components.id ASC') } //component.rb
当您执行id上升的连接变为不明确的列时,因为组件和集合都具有id列.它不知道使用哪个.