fields_for表单构建器对象为nil

Question

有没有办法访问嵌套的form_bulder.object？

## controller
@project = Project.new
@project.tasks.build

form_for(@project) do |f|
  f.object.nil? ## returns false

  fields_for :tasks do |builder|
    builder.object.nil? ## returns true
  end
end

Answer 1

您必须在Project模型中具有accepts_nested_attributes_for才能传递对象.

class Project < ActiveRecord::Base
  has_many :tasks
  accepts_nested_attributes_for :tasks ## this is required
end

Answer 2

fields_for要求该方法tasks_attributes=存在.accepts_nested_attributes_for :tasks为您创建此方法,但您也可以自己定义:

def tasks_attributes=(params)
  # ... manually apply attributes in params to tasks
end

当这种方法不存在时,builder.object最终结果为零.