Rails has_and_belongs_to_many不能与include一起使用？

Question

我正在尝试从用户中删除相同的语言。

class User < ActiveRecord::Base
   has_and_belongs_to_many :languages
end

class Language < ActiveRecord::Base
  has_and_belongs_to_many :users, uniq: true
end

但是当我尝试做的时候

    lang = Language.where(id: params[:user][:lang_1])
    @user.languages << lang

    logger.debug(@user.languages.include? Language.where(id: params[:user][:lang_1]))

include?总是返回false，即使@user.languages确实包含Language.where(id: params[:user][:lang_1])。如何修复include?方法？

Answer 1

您需要保存@user才能为用户存储新语言

    lang = Language.where(id: params[:user][:lang_1])
    @user.languages << lang
    @user.save!

    logger.debug(@user.languages.include?(lang))