Rails has_many：通过和collection_select与多个

Question

我有以下问题使用has_many：通过多选择通过collection_select：multiple => true中的多对多关系。我有供应商提供许多供应商可以交付的成分。看一看：

成分模型：

class Ingredient < ActiveRecord::Base 
    has_many :ingredient_suppliers 
    accepts_nested_attributes_for :ingredient_suppliers, :allow_destroy => true 

    has_many :suppliers, :through => :ingredient_suppliers 
end 

供应商型号：

class Supplier < ActiveRecord::Base 
    has_many :ingredient_suppliers 
    has_many :ingredients, :through => :ingredient_suppliers 
end 

的关系实体：

class IngredientSupplier < ActiveRecord::Base 
    belongs_to :ingredient 
    belongs_to :supplier 
end 

这是形式。请注意，我不能让它在不指定工作：名称：

<%= form_for(@ingredient) do |f| %> 
<%= f.fields_for :suppliers do |supplier_fields| %> 
     <%= supplier_fields.collection_select (:supplier_ids, 
      Supplier.all(:order=>"name ASC"), 
      :id, :name, 
      {:selected => @ingredient.supplier_ids, 
      :include_blank => true}, 
      {:multiple => true, 
       :name => 'ingredient[supplier_ids]'}) %> 
    <% end %> 
<% end %> 

如果我删除了：名字，然后我得到这个错误信息：

Supplier(#-617951108) expected, got Array(#-608411888) 

Request 

Parameters: 

{"commit"=>"Anlegen", 
"authenticity_token"=>"MuEYtngwThharmM1KaAbH8JD3bScXiDwj0ALMytxl7U=", 
"_method"=>"put", 
"utf8"=>"✓", 
"id"=>"1", 
"ingredient"=>{"name"=>"Ingredient 1", 
"nr"=>"00100", 
"unit"=>"kg", 
"mol_per_unit"=>"2000, 
00000", 
"description"=>"", 
"suppliers"=>{"supplier_ids"=>["1", 
"2"]}}} 

现在的问题是，该PUT参数只包含一个supplier_id而不是一个supplier_ids数组：

"ingredient"=>{"name"=>"Rohstoff 3", "nr"=>"00300", "unit"=>"Stk.", "mol_per_unit"=>"0,00000", "description"=>"", "supplier_ids"=>"2"} 

Answer 1

我已经解决了问题。在这种情况下，使用fields_for是错误。解决方法是使用一个collection_select，像这样：

<%= collection_select(:ingredient, :supplier_ids, 
       Supplier.all(:order=>"name ASC"), 
       :id, :name, {:selected => @ingredient.supplier_ids, :include_blank => true}, {:multiple => true}) %>