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最新评论
-
zhangyou1010:
回去倒立去,哈哈。
作为一个程序员,身体很重要! -
Hooopo:
Ruby MetaProgramming is all abo ...
Metaprogramming Ruby -
orcl_zhang:
yiqi1943 写道LZ现在上学还是工作呢工作好多年了。不过 ...
2011年 -
yiqi1943:
LZ现在上学还是工作呢
2011年 -
tjcjc:
query cache
就是一个简单的hash
key就是sq ...
Rails sql延迟加载和自带缓存
阅读api是一种乐趣!
api of fields_for===========
fields_for(record_or_name_or_array, *args) {|builder.new(object_name, object, self, options, block)| ...}
Creates a scope around a specific model object like form_for, but doesn‘t create the form tags themselves. This makes fields_for suitable for specifying additional model objects in the same form.
Generic Examples
…or if you have an object that needs to be represented as a different parameter, like a Client that acts as a Person:
…or if you don‘t have an object, just a name of the parameter:
Note: This also works for the methods in FormOptionHelper and DateHelper that are designed to work with an object as base, like FormOptionHelper#collection_select and DateHelper#datetime_select.
Nested Attributes Examples
When the object belonging to the current scope has a nested attribute writer for a certain attribute, fields_for will yield a new scope for that attribute. This allows you to create forms that set or change the attributes of a parent object and its associations in one go.
Nested attribute writers are normal setter methods named after an association. The most common way of defining these writers is either with accepts_nested_attributes_for in a model definition or by defining a method with the proper name. For example: the attribute writer for the association :address is called address_attributes=.
Whether a one-to-one or one-to-many style form builder will be yielded depends on whether the normal reader method returns a single object or an array of objects.
One-to-one
Consider a Person class which returns a single Address from the address reader method and responds to the address_attributes= writer method:
This model can now be used with a nested fields_for, like so:
When address is already an association on a Person you can use accepts_nested_attributes_for to define the writer method for you:
If you want to destroy the associated model through the form, you have to enable it first using the :allow_destroy option for accepts_nested_attributes_for:
Now, when you use a form element with the _delete parameter, with a value that evaluates to true, you will destroy the associated model (eg. 1, ‘1’, true, or ‘true’):
One-to-many
Consider a Person class which returns an array of Project instances from the projects reader method and responds to the projects_attributes= writer method:
This model can now be used with a nested fields_for. The block given to the nested fields_for call will be repeated for each instance in the collection:
It‘s also possible to specify the instance to be used:
When projects is already an association on Person you can use accepts_nested_attributes_for to define the writer method for you:
If you want to destroy any of the associated models through the form, you have to enable it first using the :allow_destroy option for accepts_nested_attributes_for:
This will allow you to specify which models to destroy in the attributes hash by adding a form element for the _delete parameter with a value that evaluates to true (eg. 1, ‘1’, true, or ‘true’):
api of fields_for===========
fields_for(record_or_name_or_array, *args) {|builder.new(object_name, object, self, options, block)| ...}
Creates a scope around a specific model object like form_for, but doesn‘t create the form tags themselves. This makes fields_for suitable for specifying additional model objects in the same form.
Generic Examples
<% form_for @person, :url => { :action => "update" } do |person_form| %> First name: <%= person_form.text_field :first_name %> Last name : <%= person_form.text_field :last_name %> <% fields_for @person.permission do |permission_fields| %> Admin? : <%= permission_fields.check_box :admin %> <% end %> <% end %>
…or if you have an object that needs to be represented as a different parameter, like a Client that acts as a Person:
<% fields_for :person, @client do |permission_fields| %> Admin?: <%= permission_fields.check_box :admin %> <% end %>
…or if you don‘t have an object, just a name of the parameter:
<% fields_for :person do |permission_fields| %> Admin?: <%= permission_fields.check_box :admin %> <% end %>
Note: This also works for the methods in FormOptionHelper and DateHelper that are designed to work with an object as base, like FormOptionHelper#collection_select and DateHelper#datetime_select.
Nested Attributes Examples
When the object belonging to the current scope has a nested attribute writer for a certain attribute, fields_for will yield a new scope for that attribute. This allows you to create forms that set or change the attributes of a parent object and its associations in one go.
Nested attribute writers are normal setter methods named after an association. The most common way of defining these writers is either with accepts_nested_attributes_for in a model definition or by defining a method with the proper name. For example: the attribute writer for the association :address is called address_attributes=.
Whether a one-to-one or one-to-many style form builder will be yielded depends on whether the normal reader method returns a single object or an array of objects.
One-to-one
Consider a Person class which returns a single Address from the address reader method and responds to the address_attributes= writer method:
class Person def address @address end def address_attributes=(attributes) # Process the attributes hash end end
This model can now be used with a nested fields_for, like so:
<% form_for @person, :url => { :action => "update" } do |person_form| %> ... <% person_form.fields_for :address do |address_fields| %> Street : <%= address_fields.text_field :street %> Zip code: <%= address_fields.text_field :zip_code %> <% end %> <% end %>
When address is already an association on a Person you can use accepts_nested_attributes_for to define the writer method for you:
class Person < ActiveRecord::Base has_one :address accepts_nested_attributes_for :address end
If you want to destroy the associated model through the form, you have to enable it first using the :allow_destroy option for accepts_nested_attributes_for:
class Person < ActiveRecord::Base has_one :address accepts_nested_attributes_for :address, :allow_destroy => true end
Now, when you use a form element with the _delete parameter, with a value that evaluates to true, you will destroy the associated model (eg. 1, ‘1’, true, or ‘true’):
<% form_for @person, :url => { :action => "update" } do |person_form| %> ... <% person_form.fields_for :address do |address_fields| %> ... Delete: <%= address_fields.check_box :_delete %> <% end %> <% end %>
One-to-many
Consider a Person class which returns an array of Project instances from the projects reader method and responds to the projects_attributes= writer method:
class Person def projects [@project1, @project2] end def projects_attributes=(attributes) # Process the attributes hash end end
This model can now be used with a nested fields_for. The block given to the nested fields_for call will be repeated for each instance in the collection:
<% form_for @person, :url => { :action => "update" } do |person_form| %> ... <% person_form.fields_for :projects do |project_fields| %> <% if project_fields.object.active? %> Name: <%= project_fields.text_field :name %> <% end %> <% end %> <% end %>
It‘s also possible to specify the instance to be used:
<% form_for @person, :url => { :action => "update" } do |person_form| %> ... <% @person.projects.each do |project| %> <% if project.active? %> <% person_form.fields_for :projects, project do |project_fields| %> Name: <%= project_fields.text_field :name %> <% end %> <% end %> <% end %> <% end %>
When projects is already an association on Person you can use accepts_nested_attributes_for to define the writer method for you:
class Person < ActiveRecord::Base has_many :projects accepts_nested_attributes_for :projects end
If you want to destroy any of the associated models through the form, you have to enable it first using the :allow_destroy option for accepts_nested_attributes_for:
class Person < ActiveRecord::Base has_many :projects accepts_nested_attributes_for :projects, :allow_destroy => true end
This will allow you to specify which models to destroy in the attributes hash by adding a form element for the _delete parameter with a value that evaluates to true (eg. 1, ‘1’, true, or ‘true’):
<% form_for @person, :url => { :action => "update" } do |person_form| %> ... <% person_form.fields_for :projects do |project_fields| %> Delete: <%= project_fields.check_box :_delete %> <% end %> <% end %>
# File vendor/rails/actionpack/lib/action_view/helpers/form_helper.rb, line 476 476: def fields_for(record_or_name_or_array, *args, &block) 477: raise ArgumentError, "Missing block" unless block_given? 478: options = args.extract_options! 479: 480: case record_or_name_or_array 481: when String, Symbol 482: object_name = record_or_name_or_array 483: object = args.first 484: else 485: object = record_or_name_or_array 486: object_name = ActionController::RecordIdentifier.singular_class_name(object) 487: end 488: 489: builder = options[:builder] || ActionView::Base.default_form_builder 490: yield builder.new(object_name, object, self, options, block) 491: end
发表评论
-
calendar
2012-02-24 11:04 866http://fullcalendar.vinsol.com/ ... -
ActiveRecord::Dirty
2011-11-21 10:29 786引用Track unsaved attribute chang ... -
TinyTDS
2011-09-20 09:29 853tiny_tds https://github.com/ra ... -
pandoc-ruby
2011-09-11 11:50 1197https://github.com/alphabetum/p ... -
Rails: Calling render() outside your Controllers
2011-04-28 17:15 831From:http://blog.choonkeat.com/ ... -
为什么这样才能装上
2011-02-20 10:39 1041引用u2@u2-laptop:~$ sudo gem inst ... -
Rails的transaction
2011-01-07 18:36 3055今天同事问我关于rails transaction,如 ... -
Rails sql延迟加载和自带缓存
2010-12-30 01:11 1610color_lot_manuallies = color_lo ... -
关于rhtml
2010-12-23 00:26 867在视图里有这样一段代码 sorted_op_items = o ... -
will_paginate ajax
2010-11-26 13:21 910两种方法 一, @@pagination_options ... -
save > save!(转)
2010-11-19 19:57 750Thoughtbot folks have a great a ... -
USE INDEX with Active Record finders(转)
2010-11-18 22:07 888可以通过强制指定index的方法优化find MySQL do ... -
html转义
2010-11-17 23:03 953$("#contacts").html(& ... -
Rails HTTP Status Code to Symbol Mapping
2010-11-17 22:40 1621http状态码http://zh.wikipedia.org/ ... -
Scaling Rails很不错的视频
2010-09-29 18:10 821自从railscasts开始讲解rails3后就很久没看了。 ... -
ActionController源码(待续)
2010-09-20 15:14 1022/usr/local/lib/ruby/gems/1.8/ge ... -
rails源码ActionSupport(待续)
2010-08-31 16:59 930一些奇淫技巧 class Object # An ... -
动态的增加auto_complete
2010-08-30 12:17 892http://www.iteye.com/problems/3 ... -
rails 记录
2010-08-26 15:27 737代码里有这样一句 self.purchase_invoices ... -
用Array来实现OrderedHash
2010-08-18 14:29 912偶然发现电脑的角落里有这样的一段代码.功能是用Array实现的 ...
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