Rails polymorphic 关联的 model, 在 form 中如何写成 select tag
如题
class apple < ActiveRecord::Base
belongs_to :dinner, as: :fruit
end
class peach < ActiveRecord::Base
belongs_to :dinner, as: :fruit
end
class dinner < ActiveRecord::Base
has_many :fruits, polymorphic: true
accepts_nested_attributes_for :fruits
end
如果我想 create 一个 dinner record, 希望能有一个
= form_for @dinner do |f|
= f.field_for :fruit do |p|
= p.text_field :fruit_id
= p.text_field :fruit_type
= f.submit
总不能让用户填写 id 和 class 名，有什么最好的办法把上面的两个 text_field 换成一个 select tag?
3.1 The Select and Option Tags The most generic helper is select_tag, which — as the name implies — simply generates the SELECT tag that encapsulates an options string:
<%= select_tag(:city_id, 'Lisbon...') %> This is a start, but it doesn't dynamically create the option tags. You can generate option tags with the options_for_select helper:
<%= options_for_select([['Lisbon', 1], ['Madrid', 2], ...]) %>
output:
Lisbon Madrid ... The first argument to options_for_select is a nested array where each element has two elements: option text (city name) and option value (city id). The option value is what will be submitted to your controller. Often this will be the id of a corresponding database object but this does not have to be the case.
Knowing this, you can combine select_tag and options_for_select to achieve the desired, complete markup:
<%= select_tag(:city_id, > options_for_select(...)) %> options_for_select allows you to pre-select an option by passing its value.
<%= options_for_select([['Lisbon', 1], ['Madrid', 2], ...], 2) %>
output:
Lisbon selected="selected">Madrid ... Whenever Rails sees that the internal value of an option being generated matches this value, it will add the selected attribute to that option.