Accessing an attribute on a foreign table by joining two tables in Rails ActiveRecord - sql

Question

I have a model, Message that belongs to the model User and the User model has an attribute name.
Message:
user_id
message_body
1
"hello world"
User:
user_id
name.
1
"johndoe"
The result I want is a complete list of all the messages and the respective user name that created each of those messages.
the api controller endpoint looks something like:
def index
#messages = Message.all
render json: { messages: #messages }
end
The issue is that when I return #messages it only contains the user_id that each message belongs to. What I really want is the user name
I could loop through every message and construct an entirely new object that looks something like:
#object = [
{
name: #messages[0].user.name,
message_body: #messages[0].body
},
{
name: #messages[1].user.name,
message_body: #messages[1].body
},
etc.
]
and then call render json: { messages: #object }
This would probably work fine, but it seems inefficient. Is there a better method for joining these tables for this result?
name
message body
"johndoe"
"hello world"
I was hoping the above example would be enough to get the answer I'm looking for. This is a simplified version of my architecture. In reality it's a bit more complicated:
LeagueChatMessage belongs_to LeagueChat
LeagueChatMessage belongs_to User
LeagueChat belongs_to League
League has_one LeagueChat
so this is really what the controller looks like
def index
#league = League.find_by(id: 1)
render json: { messages: #league.league_chat.league_chat_messages }
end
it works fine. It returns all the league chat messages for the league with the id: 1 but it returns the user_id for each message instead of the user name

Answer 1

Use following logic
#data = Message.includes(:user)
Now you can use like below
#data.each do |msg|
puts "Message #{msg.body}"
puts "User #{msg.user.name}"
end
I used puts for understanding but you can use this object in views as you want. And your approach leads to an n+1 query problem, so I used the includes, which helps remove the n+1 query. Try this and let me know if you have any queries.