Ruby on Rails-访问当前用户的嵌套属性

Question

i am trying to access some nested attributes in a rails partial; let me explain my issue:

i wrote a simple messaging service according to the tutorial of dana mulder i mentioned in another question of mine. a user has_many conversations , and a conversation has_many messages . every conversation has a recipient and a sender and every message has a boolean read , which is set to false by default.

what i am trying to do is to write a simple function that iterates through every message a user got in a conversation he is involved in, checks if the last message a user recieved in a conversation is read == true and not send by himself to display a little knob beside the "messages" link in the navigation of my app.

What i basically want to check is (multiple lines for better readability):

<%= if current_user.conversations.all.messages.last.user_id != current_user.id && current_user.conversations.all.messages.last.read == false %>

    Message link with bubble beside it

<% else %>

    Message link

<% end %>

This syntax does not work .. How is it possible to iterate through every conversation a user is involved, check the last message of every conversation if its written by this user and if not if its already read?

while something like Conversation.last.messages.last.content is working, current_user.conversations.all.messages.last.content is not.. i find it a bit confusing how the accessibility of rails models are working.

thanks in advance! i hope i was explaining me well enough.

Best Regards

Answer 1

What are you trying to do with current_user.conversations.all.messages.last.content ? because conversations.all is an association, it is NOT a Conversation, so messages is not an available method. Conversation.last IS a Conversation, that's why you can call messages on it.

You can try current_user.conversations.last.messages.last.content to get the last message of the last conversation, or, you can use a "has_many :through" relationship on User

class User ...
  has_many :conversations
  has_many :messages, through: :conversations
end

That way you can do current_user.messages if you want ALL user's messages and current_user.messages.last to get the last Message (even if it's not from the last conversation).

I'd recommend you to read the Rails Guide about Associations https://guides.rubyonrails.org/association_basics.html#the-has-many-through-association

EDIT: To know if the user has some unread message, you can use the has_many :through association and do something like

current_user.messages.where(read: false).where.not(user_id: current_user.id).any?

That will return true any message from the user's conversations with id != current_user.id is not read. And false otherwise.

You can use count instead of any? if you wan't to know the actual number of unread messages.