ruby-on-rails – 在fields_for中使用“：”和“@”有什么区别

这不起作用

<h1>PlayersToTeams#edit</h1>
<%= form_for @players_to_teams do |field| %>
  <%= field.fields_for @players_to_teams.player do |f| %>
    <%= f.label :IsActive %>
    <%= f.text_field :IsActive %>
  <% end %>
  <%= field.label :BT %>
  <%= field.text_field :BT %>
  <br/>
  <%= field.submit "Save",class: 'btn btn-primary' %>
<% end %>

给我一个ActiveRecord :: AssociationTypeMismatch错误.注意forms_for行中的@ players_to_teams.player.

这确实有效：

<h1>PlayersToTeams#edit</h1>
<%= form_for @players_to_teams do |field| %>
    <%= field.fields_for :player do |f| %>
        <%= f.label :IsActive %>
        <%= f.text_field :IsActive %>
    <% end %>
    <%= field.label :BT %>
    <%= field.text_field :BT %>
    <br/>
    <%= field.submit "Save",class: 'btn btn-primary' %>
<% end %>

注意：fields_for行中的：player调用.

什么是使用符号和使用实例之间的区别？我想我会想在这种情况下使用一个实例,但我猜不是吗？

编辑

楷模：

class Player < ActiveRecord::Base
  has_many :players_to_teams
  has_many :teams,through: :players_to_teams
end

class PlayersToTeam < ActiveRecord::Base
  belongs_to :player
  belongs_to :team

  accepts_nested_attributes_for :player
end

控制器：

class PlayersToTeamsController < ApplicationController
  def edit
    @players_to_teams=PlayersToTeam.find(params[:id])
  end

  def update
    @players_to_teams=PlayersToTeam.find(params[:id])
    respond_to do |format|
      if @players_to_teams.update_attributes(params[:players_to_team])
        format.html { redirect_to @players_to_teams,notice: 'Player_to_Team was successfully updated.' }
        format.json { head :no_content }
      else
        format.html { render action: "edit" }
        format.json { render json: @players_to_teams.errors,status: :unprocessable_entity }
      end
    end
  end
end

示例项目

Github：https://github.com/workmaster2n/embedded-form-errors