Ruby-on-rails 如何添加到序列化数组
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How to add to a serialized array
提问by grabury
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/序列化字段中。
class User < ActiveRecord::Base
serialize :recent_messages
end
In the controller I've tried
在我试过的控制器中
@user = current_user
@user.recent_messages << params[:message]
@user.save
but I get the following error:
但我收到以下错误：
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？
回答by Stefan
You can pass a class to serialize:
您可以将一个类传递给serialize：
class User < ActiveRecord::Base
serialize :recent_messages, Array
end
The above ensures that recent_messagesis an Array:
以上确保recent_messages是一个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.
请注意，如果类型不匹配，您可能必须转换现有字段。
回答by Hymanbot
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 nilby 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您的 时recent_messages，没有将项目推送到的数组（nil默认情况下该字段是）。所以你必须先创建数组，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
回答by techvineet
You can also try following code:- By default @user.recent_messageswould be nil
您也可以尝试以下代码：- 默认情况下@user.recent_messages为 nil
@user.recent_messages ||= []
@user.recent_messages << params[:message]
@user.save
