如何添加到序列化数组

I have an existing user which has a serialized field and I want to be able to add recent messages to the array / serialized field.

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

In the controller I've tried

在控制器中我试过了

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

but I get the following error:

但是我收到以下错误：

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

In my schema I have:

在我的架构中，我有：

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

Any ideas on where I'm going wrong?

关于我哪里出错的任何想法？

3 个解决方案

#1

You can pass a class to serialize:

您可以传递一个类来序列化：

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

The above ensures that recent_messages is an Array:

以上确保recent_messages是一个数组：

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.

请注意，如果类型不匹配，您可能必须转换现有字段。

#2

It's because the first time you try to push an item to your recent_messages, there's no array to push the item into (the field is nil by default). So you must create the array before you can push to it

这是因为第一次尝试将项目推送到recent_messages时，没有数组可以将项目推入（默认情况下该字段为nil）。因此，您必须先创建数组才能推送它

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

#3

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

您还可以尝试以下代码： - 默认情况下，@ user.recent_messages将为零

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

#1