Join different nodes to observe them at once with firebase

问题

I'm trying to do a sample application with firebase and I don't have quite understand how I should retrieve nested-flattered data.

Let's suppose I have a db like this

 {
        "users": {
            "user-1": {
                "email": "email1",
                "matches": [
                    "match-1",
                    "match-2"
                ]
            },
            "user-2": {
                "email": "email2",
                "matches": [
                    "match-1",
                    "match-2"
                ]
            },
            "user-3": {
                "email": "email3",
                "matches": [
                    "match-2"
                ]
            }
        },
        "matches": {
            "match-1": {
                "name": "Match 1",
                "users": [
                    "user-1",
                    "user-2"
                ]
            },
            "match-2": {
                "name": "Match 2",
                "users": [
                    "user-1",
                    "user-2",
                    "user-3"
                ]
            }
        }
    }

and I want to get all the match of the user-1. What I'm doing now is observe users.user-1.matches to get the matches list and then observe every match so the final flow is:

• observe users.user-1.matches
• observe matches.match-1
• observe matches.match-2
• ...

The question is: how can I optimize this flow? (like making something like the sql join)

My idea is to get something like this

{
    "users": {
        "user-1": {
            "email": "email1",
            "matches": {
                "match-1": {
                    "name": "Match 1",
                    "users": [
                        "user-1",
                        "user-2"
                    ]
                },
                "match-2": {
                    "name": "Match 2",
                    "users": [
                        "user-1",
                        "user-2",
                        "user-3"
                    ]
                }
            }
        }
    }
}

So I can observer the whole structure at once.

I'm using firebase on iOS with swift but feel free to reply in every language you like.

Thanks.

回答1:

The answer linked in the comment is an answer, but let's simplify. Let's create a users node to store the users and a matches node to track the matches they played in.

Then we'll do a query to retrieve which matches user-1 played in:

users
  user-1
    name: "some name"
    email: "somename@thing.com"
  user-2
    name: "another name"
    email: "anothername@thing.com"
  user-3
    name: "cool name"
    email: "coolname@thing.com"

and then the matches node

matches
  match-1
    name: "Match 1"
    users
        user-1: true
        user-2: true
  match-2
    name: "Match 2"
    users
        user-1: true
        user-2: true
        user-3: true
  match-3
    name: "Match 3"
    users
        user-2: true
        user-3: true

As you can see, we've structured the data to directly address our query

matchesRef.queryOrdered(byChild: "users/user-1").queryEqual(toValue: true)
                         .observe(.value, with: { snapshot in
     print(snapshot)          
});

and the snapshot will contain the nodes match-1 and match-2 but not match-3

来源：https://stackoverflow.com/questions/41015445/join-different-nodes-to-observe-them-at-once-with-firebase