I'm trying to create a chat app with groups. Players can join multiple groups. The problem that I'm facing is that I don't know how to add multiple groups to a player. If the player is joined in 1 group I could use 'Group' as key and the group name as value but with multiple groups this isn't possible. I can't create multiple 'Group' keys because then they aren't unique. Maybe an array as value for 'Group'? But I don't think this is possible. I hope someone can help me. Thanks!
You can use an array, but it's better to use an object with firebase-generated keys. See the proposed database structure below:
"root": {
"users": {
"$userId": {
...
"groups": {
"$groupId": true
}
}
},
"groups": {
"$groupId": {
...
}
}
}
I haven't coded for iOS, so the following example is in JavaScript. With the database structure above, you can add user to groups and read which groups the user is in like this:
var currentUserId = ?; // The userId of the logged in user
var currentUserGroupsRef = rootRef.child('user').child(currentUserId).child('groups');
// Join group
var groupId = ?; // The id of a group that the user joins
currentUserGroupsRef.child(groupId).set(true); // Add the groupId to the users groups, letting firebase generate an Id
// Read groups
currentUserGroupsRef.on('value', (snap) => {
if (!snap.val()) {
var userGroupIds = []; // user is not in any groups, empty array of groupIds
return;
}
var userGroupIds = Object.keys(snap.val()); // Array of groupIds
});
Related
Just for background, let us have these three domain classes:
class Group {
Long id
Person person
}
class Person {
Long id
Country country
String name
}
class Country {
Long id
}
So, with these classes in mind, I am given a Group object's id as well as a Country object's id. I would like to get the list of Person objects based on these two.
It seems relatively simple, but I am new to criteria queries and so I am struggling to figure out what I am doing wrong. This is what I have so far:
def c = Group.createCriteria()
def names = c.list (order: "asc") {
createAlias('person', 'p')
createAlias('p.country', 'c')
and {
eq ('c.id', Long.valueOf(countryId))
eq ('id', groupId)
}
projections {
property('p.name')
}
}
Of course, this is wrong as it is throwing errors. Can someone please let me know what I am doing wrong?
Thanks for your help!
static def searchPersons(Map params) {
return Group.createCriteria().list(params, {
if(params.groupId) {
eq('id', params.groupId.toLong())
}
person {
order('name')
if(params.countryId) {
country {
eq('id', params.countryId.toLong())
}
}
}
projections {
property('person')
}
})
}
Still, it might be better to add the necessary associations (hasMany, etc.) on your domains.
The first thing you can do is improve the associations between your domain classes. This will help make criteria queries simpler (and deter monkey-patching later).
In your example, the association between Person an Group is a one-to-many; one person can have many groups. That may be your intention, but it also means that a group can have only one person. Basically, there's no way to group people together.
I'm going to assume that you want a many-to-one relationship so that many Person (people) can be in the same Group. With this in mind, the domain classes (with the explicit IDs left in) would look like this:
class Group {
Long id
}
class Person {
Long id
Country country
String name
Group group
}
class Country {
Long id
}
As for the query, since your expected result is instances of Person, the best place to start is with Person rather than Group.
List of Person instances
Here's how to get a list of Person instances.
Where query
def people = Person.where {
country.id == countryId
group.id == groupId
}.list()
Criteria query
def people = Person.withCriteria {
country {
eq 'id', countryId as Long
}
group {
eq 'id', groupId
}
}
List of Person names
Notice that there's a discrepancy between your question and example. You asked for a list of Person instances, yet your example demonstrates attempting to get a list of Person names .
Here's how to get a list of names of the Person instances.
Where query
def names = Person.where {
country.id == countryId
group.id == groupId
}.projections {
property 'name'
}.list()
Criteria query
def names = Person.withCriteria {
country {
eq 'id', countryId as Long
}
group {
eq 'id', groupId
}
projections {
property 'name'
}
}
Just wondering am I doing this correctly or is there a better way.
I have 3 tables, Game, User and UserGame. The UserGame is a join table has pointers to both Game and User tables.
The following script returns all the games that the user has joined.
var Game = Parse.Object.extend("Game");
var UserGame = Parse.Object.extend("UserGame");
var innerQuery = new Parse.Query(Game);
var query = new Parse.Query(UserGame);
query.equalTo("user", user);
query.matchesQuery("game", innerQuery);
query.include("game");
query.find({
I am now trying to return the games that the user has not joined. I tried the reverse of the above query but it does not work. Any ideas?
Also is there a better solution than using the join table above, should I just add a list of game pointers to the user table?
This is userful (and not easily accessible from the website)
https://parse.com/docs/js/symbols/Parse.Query.html
What you're trying to do seems like a good usecase of .noContainerIn([results of the first query]) or .doesNotMatchKeyInQuery
matchesKeyInQuery in your first example seems simpler to use BTW
I have used a table that has two pointers inside it too.I'm going to explain what I did simplified, and adpating it to your case:
1.Build a query with your object Game,to get an array of all games that exists in this table:
var Game = Parse.Object.extend("Game");
var query = new Parse.Query(Game);
query.find({
success: function(arrayGames) {
//store this array to manage later
},
error: function(user, error) {
alert("There is not stored games");
}
});
2. Get the user you want to compare to this games stored that points in the table UserGame, and make a Query for each element of the previous got array:
var UserGame = Parse.Object.extend("UserGame");
var query = new Parse.Query(UserGame);
var currentUser = Parse.User.current();
var currentGame;
for(var i=0; i<arrayGames.length ;i++){
currentGame=arrayGames[i];
query.equalTo("Game", currentGame);
query.notEqualTo("User", currentUser);
query.find({
success: function(foundGames) {
//you have got an array with the games not joined to this user
},
error: function(user, error) {
alert("There are not joined games ");
}
});
}
Hope it helps, ask me if you need more details ;)
I have two parse classes; Companies and Ratings. It is a one to many relationship. Companies can have many Ratings. This is the statement I would perform in SQL:
SELECT Companies.name, Ratings.rating
FROM Companies
INNER JOIN Ratings
ON Ratings.name_id = Companies.name_id
ORDER BY Companies.name
I want the equivalent of this in Parse, but I'm not sure of how to go about it. Here is what I've currently tried:
function getRatings() {
var tableA = new Parse.Query(Companies);
var tableB = new Parse.Query(Ratings);
tableB.equalTo("name_id", tableA.name_id);
tableB.find({
success: function(results) {
$scope.$apply(function() {
$scope.companies = results.map(function(obj) {
return {
id: obj.get("name_id"),
name: obj.get(tableA.name),
rating: obj.get("rating"),
parseObject: obj
};
});
});
},
error: function(error) {
alert("Error: " + error.code + " " + error.message);
}
});
}
I am calling this function when the controller loads. This code displays the rating in my output, but not the name of the company.
I am trying to get all the companies listed in the companies object, then pair them with all the ratings they have in the ratings object. Their common key is name_id. This is the code I am using within my Angular view:
<div class="span12">
<div ng-repeat="company in companies | filter: query | orderBy: orderList"
class="well company-description">
<h1>{{company.name}}</h1>
<h3>Rating: {{company.rating}}</h3>
</div>
</div>
If I am way off base on this, please let me know
Get rid of the name_id column in the Ratings class. This isn't how you're supposed to define relationship using Parse.
There are a couple of options for you to choose.
Option 1
Using the Parse data browser, add a new column under the Companies class, called ratings. It should be a column of type Relation and point to Ratings as the target class. (Let me know if you need more information on how to do this.)
Then, when you create or edit a company, add ratings as follows:
var Companies = Parse.Object.extend("Companies");
var Ratings = Parse.Object.extend("Ratings");
var company = new Companies({name: "Some Company"});
company.relation("ratings").add(new Ratings({stars: 5}));
company.save();
Then, when querying Companies, do so as follows:
new Parse.Query(Companies).find({
success: function(companies) {
for (var i = 0; i < companies.length; i++) {
companies[i].relation("ratings").query().find({
success: function(ratings) {
// Finally, I have the ratings for this company
}
}
}
}
});
Option 2
Using the Parse data browser, add a new column under the Companies class, called ratings. It should be a column of type Array.
Then, when you create or edit a company, add ratings as follows:
var Companies = Parse.Object.extend("Companies");
var Ratings = Parse.Object.extend("Ratings");
var company = new Companies({
name: "Some Company",
ratings: [new Ratings({stars: 5})]
});
company.save();
Then, when querying Companies, do so as follows:
new Parse.Query(Companies).include("ratings").find({
success: function(companies) {
// Yay, I have access to ratings via companies[0].get("ratings")
}
});
include("ratings") tells Parse to include the actual objects, rather than pointers to objects for the given key.
Conclusion
Option 1 is better if you are expecting to have a large amount of ratings for each company, and if you don't always plan on retrieving all the ratings each time you query the companies.
Option 2 is better if the number of ratings for each company is relatively small, and you always want ratings to come back when you query companies.
I found out how to resolve the Uncaught You can't add an unsaved Parse.Object to a relation. error.
var addRating = new Ratings({stars: rating}); // save rating first, then associate it with a company
addRating.save({
success: function() {
var addCompany = new Companies({name: name});
addCompany.relation("ratings").add(addRating);
addCompany.save();
}
});
The rating has to be saved first, then the company relation can be added later on... makes sense, but took me awhile to figure it out! :S
Some pseudo-code of the model I'm working with:
User { int Id, string Username }
Activity { int Id, string Name }
Place { int Id, string Name }
Basically I have a bunch of Users and they belong to certain places (many to many relationship in RDBMS world). What I'd like to do now that I've created all of the nodes already is create the relationship between them. To do that I believe I need to get references to each node and then simply create the relationship between them.
Note: So far no relationships exist. It does look like in some of the examples they have added the User nodes with a relationship that points to the RootNode but I have no idea why. I'm not sure if I need to do that or not.
More pseudo-code:
var userRef = _graphClient...GetUserNodeWhereIdEquals(user.Id);
// or something like _graphClient.OutV<User>("[[id={0}]]", user.Id)
// or even just _graphClient.V<User>(id == user.Id)
var placeRef = _graphClient...GetPlaceNodeWhereIdEquals(place.Id);
_graphClient...CreateRelationshipBetween(userRef, placeRef, "belongs_to");
Unfortunately the documentation starts off pretty great then goes south when you get to relationships.
Update 3/29/12
Here's the code I have so far:
foreach (var a in _activityTasks.GetAll())
{
_graphClient.Create(a, new ActivityBelongsTo(_graphClient.RootNode));
}
foreach (var p in _placeTasks.GetAll().Take(1))
{
var placeNode = _graphClient.Create(p, new PlaceBelongsTo(_graphClient.RootNode));
foreach (var activity in p.Activities)
{
Activity activity1 = activity;
var activityNode = _graphClient.RootNode.In<Activity>(ActivityBelongsTo.TypeKey, a => a.Id == activity1.Id).SingleOrDefault();
_graphClient.CreateRelationship(placeNode, new PlaceHasActivity(activityNode.Reference));
}
}
The activity nodes are created fine. The place node is created fine. An error is now being thrown when trying to get the activityNode. It's a rather large stack trace so I'll try to paraphrase here:
Received an exception when executing the request.
The query was: g.v(p0).in(p1).filter{ it[p2] == p3
}.drop(p4).take(p5)._()
The exception was: Value cannot be null. Parameter name: key
System.ArgumentNullException: Value cannot be null.Parameter name: key
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue
value, Boolean add) ... The raw response body was: [ {
"outgoing_relationships" :
"http://localhost:7474/db/data/node/2/relationships/out", "data" : {
"Name" : "Aerobics", "Id" : 2 }, "all_typed_relationships" :
"http://localhost:7474/db/data/node/2/relationships/all/{-list|&|types}",
"traverse" :
"http://localhost:7474/db/data/node/2/traverse/{returnType}", "self"
: "http://localhost:7474/db/data/node/2", "property" :
"http://localhost:7474/db/data/node/2/properties/{key}",
"outgoing_typed_relationships" :
"http://localhost:7474/db/data/node/2/relationships/out/{-list|&|types}",
"properties" : "http://localhost:7474/db/data/node/2/properties",
"incoming_relationships" :
"http://localhost:7474/db/data/node/2/relationships/in", "extensions"
: { }, "create_relationship" :
"http://localhost:7474/db/data/node/2/relationships",
"paged_traverse" :
"http://localhost:7474/db/data/node/2/paged/traverse/{returnType}{?pageSize,leaseTime}",
"all_relationships" :
"http://localhost:7474/db/data/node/2/relationships/all",
"incoming_typed_relationships" :
"http://localhost:7474/db/data/node/2/relationships/in/{-list|&|types}"
} ]
Something to do when adding a item to a Dictionary when the key is null. Problem is, I don't see any nulls when I debug on my end, activity1 is there, RootNode is there, TypeKey is a const string.
I'm almost wondering if I should just keep the created nodes within a array or Dictionary myself and then just working with the NodeReference. That's what I'm going to try next.
Later that morning
This seems to load everything into the graph database fine:
var activityNodes = _activityTasks.GetAll().ToDictionary(a => a.Id, a => _graphClient.Create(a, new ActivityBelongsTo(_graphClient.RootNode)));
foreach (var p in _placeTasks.GetAll())
{
var placeNode = _graphClient.Create(p, new PlaceBelongsTo(_graphClient.RootNode));
foreach (var activity in p.Activities)
{
_graphClient.CreateRelationship(placeNode, new PlaceHasActivity(activityNodes[activity.Id]));
}
}
foreach (var u in _userTasks.GetAllUserGraph())
{
var userNode = _graphClient.Create(u, new UserBelongsTo(_graphClient.RootNode));
foreach(var activity in u.Activities)
{
_graphClient.CreateRelationship(userNode, new UserParticipatesIn(activityNodes[activity.Id]));
}
}
Now the problem is similar to what I had before. Now I want to get an activity that has a relationship to the RootNode:
Node<Activity> activity = _graphClient
.RootNode
.In<Activity>(ActivityBelongsTo.TypeKey, a => a.Id == 1)
.SingleOrDefault();
Throwing the key value can't be null exception again. I think I need to investigate the gremlin syntax more. I'm guessing the problem is there.
This afternoon
Started to experiment with Gremlin queries:
g.v(0).inE.filter{it.label=="ACTIVITY_BELONGS_TO"}.outV.filter{it.Id==1}.Name
works fine. I tried to replicate that using neo4jClient syntax:
_graphClient.RootNode.InE(ActivityBelongsTo.TypeKey).OutV(b => b.Id == 1).SingleOrDefault();
Same null exception, it spits out:
g.v(p0).inE.filter{ it[p1].equals(p2) }.outV.filter{ it[p3] == p4 }.drop(p5).take(p6)._()
which looks right to me, except for the end. Ran this though:
g.v(0).inE.filter{it.label=="ACTIVITY_BELONGS_TO"}.outV.filter{it.Id==1}.drop(0).take(1)._()
And that works fine. Something stinks here...maybe I should try the other library although I liked the de/serialization support. Sigh...
Thought maybe a raw query would work. Nope! This method no longer accepts a string and the required GremlinQuery I have no idea how to you. Grooooooooooooooooan.
var users = graphClient.ExecuteGetAllNodesGremlin<IsCustomer>("g.v(0).out('IsCustomer'){it.'Name' == 'BobTheBuilder'}");
Update 3/30/12
Created a new project, everything below works fine. Super confused why it will work here... :( Maybe version differences, I have no idea.
var client = new GraphClient(new Uri("http://localhost:7474/db/data"));
client.Connect();
client.Create(new User { Id = 1, Username = "joe" }, new UserBelongsTo(client.RootNode));
client.Create(new User { Id = 2, Username = "cloe" }, new UserBelongsTo(client.RootNode));
client.Create(new Activity { Id = 1, Name = "Bocce Ball" }, new ActivityBelongsTo(client.RootNode));
client.Create(new Activity { Id = 2, Name = "Programming" }, new ActivityBelongsTo(client.RootNode));
var user = client.RootNode.In<User>(UserBelongsTo.TypeKey, u=>u.Id == 1).SingleOrDefault();
var activity = client.RootNode.In<Activity>(ActivityBelongsTo.TypeKey, a=>a.Id == 1).SingleOrDefault();
client.CreateRelationship(user.Reference, new Plays(activity.Reference));
user = client.RootNode.In<User>(UserBelongsTo.TypeKey, u => u.Id == 1).SingleOrDefault();
activity = client.RootNode.In<Activity>(ActivityBelongsTo.TypeKey, a => a.Id == 1).SingleOrDefault();
I'm just getting started too. I would suggest you check out this blog:
http://romikoderbynew.com/2011/07/30/neo4jclient-primer/
Also, check http://frictionfree.org and its source code (in the about section) for more examples.
Creating relationships on existing - as I understand, this is possible. However, it appears to be easier to associate nodes as you create them. From the blog:
You can also create relationships between existing nodes.
graphClient.CreateRelationship(customerNodeReference, new
Speaks(languageNode.Reference));
RootNode - I believe you need to start a query from a node, I don't think you can do a
SELECT * FROM ... WHERE
Therefore, it would make sense that you need to attach nodes to the root node. This is an example from the FrictionFreeApp:
var node = graphClient.Create(
user,
new UserBelongsTo(rootNode));
Using linqtosql, how would I get a colleciton of User objects, if I have an array of UserID's that I want to fetch?
You can use Contains to check if each UserID is in the array that you have.
int[] userIDs = ...
var users = db.Users.Where( u => userIDs.Contains( u.UserID ) );
If you want to avoid a SET operation and user chained ORs instead, you can use the PredicateBuilder to help you with that.
It goes something like this:
var userIDs = new[] { 1, 2, 3, 4, 5 };
// build multiple OR expressions
var filter = PredicateBuilder.False<User>();
foreach (var id in userIDs) {
filter = filter.Or(x => x.UserID == id);
}
// fetch data
using (var db = new TheDataContext()) {
var users = db.Users.Where(filter);
// wham! - we have users now.
}
Take a look at the blog post to understand how it works. This basically creates a long chaining ORs for each user id in the list before passing it to a WHERE clauses.
Try this:
using(var db=new MyDataContext())
{
var users=db.Users.Where(u=>userIds.Contains(u.Id));
}