ruby-on-rails - 如何添加到序列化数组

Question

我有一个现有用户，它有一个序列化字段，我希望能够将最近的消息添加到数组/序列化字段。

class User < ActiveRecord::Base
 serialize :recent_messages
end

在我试过的控制器中

@user = current_user
@user.recent_messages << params[:message]
@user.save

但我收到以下错误：

NoMethodError (undefined method `<<' for nil:NilClass):

在我的架构中，我有：

create_table "users", :force => true do |t|
    t.text     "recent_messages"
  end

关于我哪里出错的任何想法？

Answer 1

You can pass a class to serialize:

class User < ActiveRecord::Base
  serialize :recent_messages, Array
end

The above ensures that recent_messages is an Array:

User.new
#=> #<User id: nil, recent_messages: [], created_at: nil, updated_at: nil>

Note that you might have to convert existing fields if the types don't match.

Answer 2

这是因为当您第一次尝试将项目推送到您的recent_messages时，没有将项目推送到的数组（该字段nil默认为）。因此，您必须先创建数组，然后才能推送到它

@user = current_user
if @user.recent_messages.nil?
  @user.recent_messages = [params[:message]]
else
  @user.recent_messages << params[:message]
end
@user.save

Answer 3

You can also try following code:- By default @user.recent_messages would be nil

@user.recent_messages ||= []
@user.recent_messages << params[:message]
@user.save