Sails.js Same Model many to many association
Sails.js .10 rc8
I've completely run out of ideas for this
I have a model called User and I want to associate it in a collection to other users like a friends list. Like a many-to-many association
//User.js
friends: {
collection: 'user',
via: 'friends'
}
but when I run .populate('friends') it doesn't populate anything. Any ideas?
I find that the best way to implement this is actually adding a reference to the id .
Check this User model:
module.exports = {
attributes: {
name: {
type: 'string',
required: true,
minLength: 2
},
email: {
type: 'email',
required: true,
unique: true
},
friends: {
collection: 'user',
via: 'id'
}
}
};
Now, if you run sails console you can test the following commands:
User.create({name:'test',email:'test@test.com'}).exec(console.log);
It returns:
{ name: 'test',
email: 'test@test.com',
createdAt: '2016-12-01T22:06:19.723Z',
updatedAt: '2016-12-01T22:06:19.723Z',
id: 1 }
You created your first user. Lets create some other ones:
User.create({name:'test2',email:'test2@test.com'}).exec(console.log);
Resulting in:
{ name: 'test2',
email: 'test2@test.com',
createdAt: '2016-12-01T22:06:40.808Z',
updatedAt: '2016-12-01T22:06:40.808Z',
id: 2 }
Let's see what we have so far:
User.find().populate('friends').exec(console.log);
[ { friends: [],
name: 'test',
email: 'test@test.com',
createdAt: '2016-12-01T22:06:19.723Z',
updatedAt: '2016-12-01T22:06:19.723Z',
id: 1 },
{ friends: [],
name: 'test2',
email: 'test2@test.com',
createdAt: '2016-12-01T22:06:40.808Z',
updatedAt: '2016-12-01T22:06:40.808Z',
id: 2 } ]
Now, let's create a user with a friend, using the reference to the first user. Notice that I just pass a single id, not an array:
User.create({name:'test3',email:'test3@test.com', friends:1}).exec(console.log);
Now, the result is this one. Notice that "friends" does not appear. This is by design.
{ name: 'test3',
email: 'test3@test.com',
createdAt: '2016-12-01T22:07:34.988Z',
updatedAt: '2016-12-01T22:07:34.994Z',
id: 3 }
Let's do a find with populate to see the current status:
User.find().populate('friends').exec(console.log);
Now we see that the third user has friends. The others have an empty array.
[ { friends: [],
name: 'test',
email: 'test@test.com',
createdAt: '2016-12-01T22:06:19.723Z',
updatedAt: '2016-12-01T22:06:19.723Z',
id: 1 },
{ friends: [],
name: 'test2',
email: 'test2@test.com',
createdAt: '2016-12-01T22:06:40.808Z',
updatedAt: '2016-12-01T22:06:40.808Z',
id: 2 },
{ friends:
[ { name: 'test',
email: 'test@test.com',
createdAt: '2016-12-01T22:06:19.723Z',
updatedAt: '2016-12-01T22:06:19.723Z',
id: 1 } ],
name: 'test3',
email: 'test3@test.com',
createdAt: '2016-12-01T22:07:34.988Z',
updatedAt: '2016-12-01T22:07:34.994Z',
id: 3 } ]
Let's create a fourth one, this time with two friends:
User.create({name:'test4',email:'test4@test.com', friends:[1,2]}).exec(console.log);
Resulting in (again, no friends property):
{ name: 'test4',
email: 'test4@test.com',
createdAt: '2016-12-01T22:07:50.539Z',
updatedAt: '2016-12-01T22:07:50.542Z',
id: 4 }
This time, we passed an array of ids to friends . Let's see the current status:
User.find().populate('friends').exec(console.log);
[ { friends: [],
name: 'test',
email: 'test@test.com',
createdAt: '2016-12-01T22:06:19.723Z',
updatedAt: '2016-12-01T22:06:19.723Z',
id: 1 },
{ friends: [],
name: 'test2',
email: 'test2@test.com',
createdAt: '2016-12-01T22:06:40.808Z',
updatedAt: '2016-12-01T22:06:40.808Z',
id: 2 },
{ friends:
[ { name: 'test',
email: 'test@test.com',
createdAt: '2016-12-01T22:06:19.723Z',
updatedAt: '2016-12-01T22:06:19.723Z',
id: 1 } ],
name: 'test3',
email: 'test3@test.com',
createdAt: '2016-12-01T22:07:34.988Z',
updatedAt: '2016-12-01T22:07:34.994Z',
id: 3 },
{ friends:
[ { name: 'test',
email: 'test@test.com',
createdAt: '2016-12-01T22:06:19.723Z',
updatedAt: '2016-12-01T22:06:19.723Z',
id: 1 },
{ name: 'test2',
email: 'test2@test.com',
createdAt: '2016-12-01T22:06:40.808Z',
updatedAt: '2016-12-01T22:06:40.808Z',
id: 2 } ],
name: 'test4',
email: 'test4@test.com',
createdAt: '2016-12-01T22:07:50.539Z',
updatedAt: '2016-12-01T22:07:50.542Z',
id: 4 } ]
Now, how do you add a friend to an existing user? It's somehow odd: you have to first find the user, then use the add function on the resulting model, and then, save it. In my day to day code, I have a helper function that does just that. So, here is the example:
User.findOne(1).populate('friends').exec(function(err,u){ u.friends.add(3);u.save(function(err){ if(err) console.error(err);});});
Now in the console we see no results. Let's check the User content now:
User.find().populate('friends').exec(console.log);
[ { friends:
[ { name: 'test3',
email: 'test3@test.com',
createdAt: '2016-12-01T22:07:34.988Z',
updatedAt: '2016-12-01T22:07:34.994Z',
id: 3 } ],
name: 'test',
email: 'test@test.com',
createdAt: '2016-12-01T22:06:19.723Z',
updatedAt: '2016-12-01T22:09:41.410Z',
id: 1 },
{ friends: [],
name: 'test2',
email: 'test2@test.com',
createdAt: '2016-12-01T22:06:40.808Z',
updatedAt: '2016-12-01T22:06:40.808Z',
id: 2 },
{ friends:
[ { name: 'test',
email: 'test@test.com',
createdAt: '2016-12-01T22:06:19.723Z',
updatedAt: '2016-12-01T22:09:41.410Z',
id: 1 } ],
name: 'test3',
email: 'test3@test.com',
createdAt: '2016-12-01T22:07:34.988Z',
updatedAt: '2016-12-01T22:07:34.994Z',
id: 3 },
{ friends:
[ { name: 'test',
email: 'test@test.com',
createdAt: '2016-12-01T22:06:19.723Z',
updatedAt: '2016-12-01T22:09:41.410Z',
id: 1 },
{ name: 'test2',
email: 'test2@test.com',
createdAt: '2016-12-01T22:06:40.808Z',
updatedAt: '2016-12-01T22:06:40.808Z',
id: 2 } ],
name: 'test4',
email: 'test4@test.com',
createdAt: '2016-12-01T22:07:50.539Z',
updatedAt: '2016-12-01T22:07:50.542Z',
id: 4 } ]
With this method, you can even add the same user to the friends collection!
User.findOne(1).populate('friends').exec(function(err,u){ u.friends.add(1);u.save(function(err){ if(err) console.error(err);});});
Have fun!
Your models should look like this...
//User.js
friends: {
collection: 'friend',
via: 'user'
}
//Friend.js
user: {
model: 'user'
via: 'friends'
}
Also sails 10 rc8 is old. You should be on sails 10.5
你应该使用.populate('friends')而不是.populate(friends)
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