问题：可以正常新建 BpFeatureName 和 BpFeatureValue，但是在更新修改嵌套表单的时候，BpFeatureName 可以正常修改，但是嵌套的表 BpFeatureValue 会新增数据，代码如下：

BpFeatureName 和 BpFeatureValue 一对多关系，如下：

class BpFeatureName < ApplicationRecord

has_many :bp_feature_values, :dependent => :delete_all

belongs_to :user

accepts_nested_attributes_for :bp_feature_values

end

class BpFeatureValue < ApplicationRecord

belongs_to :bp_feature_name

end

new 和 edit 的 controller 如下

class BpFeatureNamesController < ApplicationController

def new

@bp_feature_name = BpFeatureName.new

@bp_feature_name.bp_feature_values.build

end

def create

@bp_feature_name = current_user.bp_feature_names.build(bp_feature_name_params)

if @bp_feature_name.save ...

end

end

def edit

@bp_feature_name = BpFeatureName.find(params[:id])

end

def update

if @bp_feature_name.update(bp_feature_name_params)

.....

end

end

def bp_feature_name_params

params.require(:bp_feature_name).permit(:name,:user_id, bp_feature_values_attributes: [:value])

end

end

new 和 edit 的_form 如下：

<%= form_with(model: bp_feature_name, local: true, class: "form form-horizontal") do |form| %>

<%= label_tag :name,'特征名', class:"col-sm-2 control-label" %>

<%= form.text_field :name , class: "form-control" %>

<%= form.label :value,'特征值', class:"col-sm-2 control-label" %>

<%= form.fields_for :bp_feature_values,@bp_feature_name.bp_feature_values do |bp_feature_values_form| %>

<%= bp_feature_values_form.text_field :value , class: "form-control"%>

<% end %>

<%= form.submit '创建', class:"btn btn-primary" %>

<%= link_to '返回', bp_feature_names_path ,class:"btn btn-default"%>

<% end %>