Rails如何自动关联模型中的对象？

Question

我试图在创建顺序对象和创建pdata对象之后将顺序obtecj与pdata对象关联。

，但创造的秩序并没有得到pdata_id

有人知道怎么做这个之后？

class Order < ActiveRecord::Base 

    belongs_to :product 
    belongs_to :pdata 

    after_create :create_pdata 

    def create_pdata 
    or_id = order.id 
    pr_id = product.id 

    data = Pdata.find_by_id(pr_id) 
    if data.nil? 
     attrs = product.attributes 
     attrs.delete('created_at') 
     attrs.delete('updated_at') 
     data = Pdata.create(attrs) 

     data = data.or_id 

     data.save 
    end 
    end 
end 

Answer 1

应该

unless data.nil 
end 

OR

if data.present? 
end 

Answer 2

试着改变方法本

class Order < ActiveRecord::Base 

    belongs_to :product 
    belongs_to :pdata 

    after_create :create_pdata 

    def create_pdata 
    pdata = Pdata.find_by_id(product) 
    unless pdata 
     attrs = product.attributes.slice(:list, :of, :attributes. :you, :want) 
     pdata = Pdata.create(attrs) 
     self.pdata = pdata 
     self.save 
    end 
    end 
end 

Answer 3

class Order < ActiveRecord::Base 

    belongs_to :product 
    belongs_to :pdata 

    # only initialize pdata when :pdata is not yet set (this can happen on `create` or on `update`). Change `before_save` to `before_create` if necessary. 
    before_save :initialize_pdata, unless: :pdata 

    def initialize_pdata 
    # initialize `pdata` with the attributes of the `product` record, only except `created_at`, `updated_at`, and `id`. Remove `id` below if you also want to copy the `id`. 
    # this method is called at `before_save`, so even if this is just initialised at the moment, when already "saving", this will also save/persist this initialised `pdata` object into the DB. 
    self.pdata = Pdata.new(
     product.attributes.except('created_at', 'updated_at', 'id') 
    ) 
    end 
end