用 grape 编写api/users/sign_up.json 代码

resource :users do
   post "sign_up" do
      # 不添加下面这句，会出现ActiveModel::ForbiddenAttributesError - ActiveModel::ForbiddenAttributesError:错误
      # 添加了后出现TypeError - no implicit conversion of Symbol into String:错误
      user_params = params.require(:user).permit(:email, :password, :password_confirmation)
      @user = User.new(user_params)
      if (params[:user][:password].length > 8) && (params[:user][:password] == params[:user][:password_confirmation]) && @user.save
        { :success => 1, :auth_token => @user.authentication_token, :email => @user.email }
      else
        { :success => 0, :auth_token => "", :email => "" }
      end
    end
end

不添加下面这句，会出现 ActiveModel::ForbiddenAttributesError - ActiveModel::ForbiddenAttributesError:错误 添加了后出现 TypeError - no implicit conversion of Symbol into String:错误 user_params = params.require(:user).permit(:email, :password, :password_confirmation) GG 过，解决不了！ 这个错误怎么解决？