I am doing a practice app on an instagram like app on firebase and swift. The question I have is that I am finding myself nesting my firebase "observeSingleEventOfType" to obtain all the data I need such that I can put it in my "Post Class". I was wondering if there is a better way of doing it as it seems like it could take up alot of time just to load one post? (I am grabing one info, wait, then grab the next, wait, then grab the next,wait,grab the next... and put everything as one Post Item at the end of the chain)
Upon initial load, I need the location, top comments, whether or not the user liked the post, whether the user followed the post or not. Currently what I am doing is
->Create a geo query, grab the geo information. Inside the completion block, I have a observeSingleEventOfType to look for information from my posts node and store as dictionary. Inside the completion block of this, I create another observeSingleEventOfType call to get the top comments, then inside this completionblock, I create another observeSingleEventOfType to look for whether or not the user is following the post. Then inside this, I have all the data to store inside my Post class that looks like
init(postKey: String, distance: Double, topComments: [Comment], liked: Bool, followingPost: Bool, dictionary: Dictionary<String, AnyObject>) {}
Here is my Json structure.
{
"comments" : {
"postKEY123" : {
"CommentKEY123" : {
"comment" : "aa"
}
}
},
"follow" : {
"userId123" : {
"postKEY123" : true
}
},
"posts" : {
"postKEY123" : {
"commentCount" : 1,
"postDescription" : "Aa",
"likeCount" : 0,
"userId" : "userId123"
}
},
"users" : {
"userId123" : {
"email" : "user1#mail.com"
"liked" : {
"postKey123": true
}
},
}
"location" : {
"postKey123" : {
".priority" : "9q9hrjj7cd",
"g" : "9q9hrjj7cd",
"l" : [ 37.33769226, -122.02885785 ]
},
},
}
The reason that I have done it this way is so that the Json data is not nested. As an possible alternative method, would it be possible to fetch all the data for the post async in background and return it when all the info for that post is ready? I didnt think I could do that as you wouldnt be able to guarantee what and when the item comes back. This is why I grabbed the data one by one inside completion block of one another?
Thanks,
Related
I'm new to MongoDB as well as to MongoDB Realm Sync. I was following the Realm Sync tutorial and Realm data model docs, but I wanted to learn more so I tweaked the Atlas collection structure as follows.
Projects > Tasks // i.e. tasks is a sub-collection in each project.
What I don't know is how to come up with Realm Sync Schema which can support Atlas sub-collections.
The best I came up with is a Schema where Tasks are modelled as an array within the Project. But, I'm worried that this can hit the 16MB (although a lot!) document limit for projects with a lot of the tasks.
{
"bsonType": "object",
"properties": {
"_id": {
"bsonType": "objectId"
},
"_partition": {
"bsonType": "string"
},
"name": {
"bsonType": "string"
},
"tasks": {
"bsonType": "array",
"items": {
"bsonType": "object",
"title": "Task",
"properties": {
"name": {
"bsonType": "string"
},
"status": {
"bsonType": "string"
}
}
}
}
},
"required": [
"_id",
"_partition",
"name",
],
"title": "Project"
}
Looking forward on how to model sub-collection the right way.
Edit
Here's my client side Realm models.
import Foundation
import RealmSwift
class Project: Object {
#objc dynamic var _id: String = ObjectId.generate().stringValue
#objc dynamic var _partition: String = "" // user.id
#objc dynamic var name: String = ""
var tasks = RealmSwift.List<Task>()
override static func primaryKey() -> String? {
return "_id"
}
}
class Task: EmbeddedObject {
#objc dynamic var name: String = ""
#objc dynamic var status: String = "Pending"
}
As far the CRUD operations are concerned, I only create a new project and read existing projects as follows.
// Read projects
realm.objects(Project.self).forEach { (project) in
// Access fields
}
// Create a new project
try! realm.write {
realm.add(project)
}
Your code looks great and your heading the right direction, so this answer is more explanation and suggestions on modeling than hard code.
First, Realm objects are lazily loaded which means they are only loaded when used. Tens of thousands of objects will have very little impact on a devices memory. So suppose you have 10,000 users and you 'load them all in'
let myTenThousandUsers = realm.objects(UserClass.self)
meh, no big deal. However, doing this
let someFilteredUsers = myTenThousandUsers.filter { $0.blah == "blah" }
will (could) create a problem - if that returns 10,000 users they are all loaded into memory possibly overwhelming the device. That's a Swift function and 'converting' Realms lazy data using Swift should generally be avoided (use case dependent)
The observation of this code using Swift .forEach
realm.objects(Project.self).forEach { (project) in
// Access fields
}
could cause issues depending on what's being done with those project objects - using them as a tableView dataSource could be trouble if there are a lot of them.
Second thing is the question about the 16Mb limit per document. For clarity an Atlas document is this
{
field1: value1,
field2: value2,
field3: value3,
...
fieldN: valueN
}
where value can be any of the BSON data types such as other documents, arrays, and arrays of documents.
In your structure, the var tasks = RealmSwift.List<Task>() where Task is an embedded object. While conceptually embedded objects are objects, I believe they count toward a single document limit because they are embedded (correct me if I am wrong); as the number of them grows, the size of the enclosing document grows - keeping in mind that 16Mb of text is an ENORMOUS of text so that would/could equate to millions of tasks per project.
The simple solution is to not embed them and have them stand on their own.
class Task: Object {
#objc dynamic var _id: String = ObjectId.generate().stringValue
#objc dynamic var _partition: String = ""
#objc dynamic var name: String = ""
#objc dynamic var status: String = "Pending"
override static func primaryKey() -> String? {
return "_id"
}
}
Then each one can be 16Mb, and an 'unlimited number' can be associated with a single project. One advantage of embedded objects is a type of cascade delete where when the parent object is deleted, the child objects are as well, but with a 1-many relationship from Project to Tasks - deleting a bunch of tasks belonging to a parent is easy.
Oh - another case for not using embedded objects - especially for this use case - is they cannot have indexed properties. Indexing can greatly speed up some queries.
I have the following data structure:
"feed" : {
"756135 Washington" : {
"VbMvwmlNqGNUY44JmfPp" : {
"downvotes" : "downvotes",
"timestamp" : 1483396793247,
"upvotes" : {
"i5KHwJzhTTfA6FJ8Fb2qLHuLjHi2" : {
"timestamp" : 1483396826253
}
},
}
}
}
Now I want to remove the i5KHwJzhTTfA6FJ8Fb2qLHuLjHi2 node under upvotes but I still want the upvotes node to stay, just without any children. I'm using the following code, however this removes the whole node.
ref?.child("feed").child(city_localizer_string!).child(id!).child("upvotes").child(uid).removeValue()
Anything empty in firebase will always be removed automatically. Even if you try and create a new child with the value of nil it won't be added to your database.
I have the following structure in my firebase database.
"friendRequest" : {
"uid" : {
"-KUT7mxTW7WGLkgrZVM4" : {
"fromUid" : "uid"
}
}
}
In my iOS app, a user can make a friend request, similar in principle to adding friends on Facebook.
I need to access the fromUid property but I don't know the parent key above it which is generated by childByAutoId() (the third line - "-KUT7mxTW7WGLkgrZVM4").
How can I access the fromUid key to get its value?
I think you're looking for something like:
ref.child("friendRequest")
.child(FIRAuth.auth()?.currentUser.uid)
.queryOrdered(byChild: "fromId")
.queryEqual(toValue: "theUidThatYou'reLookingFor")
.observeSingleEvent(of: .childAdded, with: { (snapshot) in
print("\(snapshot.key)")
})
I am searching for a good example of a composite control.
My current problem is, that I plan to bind a simple value (for example a string) that will be reused in some other control inside a composite control.
Following code seems not correct:
metadata : {
properties : {
"head" : {type : "string", defaultValue : ""},
...
},
},
init : function() {
... some control with content ...
content : [
new sap.m.Label({text : this.getHead()})
]
...
My plan to call the composite control would look like this:
var oTemplate = new MyControl({ head : "{Name}" });
Using the template for example in a list.
Binding may work, but because of the fact that I build the control in the "init" part it looks like the property is not initialised and will not be updated automatically.
A further experiment (that will not work):
jQuery.sap.declare("StrangeControl");
sap.m.HBox.extend("StrangeControl", {
metadata : {
properties : {
},
aggregations : {
input : {type : "sap.m.Input", multiple : false},
}
},
// will be called during creation time
init : function() {
sap.m.HBox.prototype.init.call(this);
this.addItem(this.getAggregation("input"));
},
renderer : {},
onAfterRendering : function() {
if (sap.m.HBox.prototype.onAfterRendering!==undefined) {
sap.m.HBox.prototype.onAfterRendering.call(this);
}
}
});
I assume to use the control that way:
new StrangeControl({
input : new sap.m.Input({value : "test"})
})
But during init input is not defined (==null). The mentioned example https://github.com/SAP/openui5/blob/master/src/sap.m/src/sap/m/SelectDialog.js seems to handle the "items" in a different way but for me it is not clear how.
Meanwhile there a documentation exists (at least in OpenUI5beta SDK).
https://openui5.hana.ondemand.com/#/topic/c1512f6ce1454ff1913e3857bad56392
If the link does not work search for "Composite Controls" inside the "DEVELOPER GUIDE" section.
A: Just add your internal control to a hidden aggregation - it will automatically get all the data binding for free, you just have to bind the properties/aggregations of that control accordingly.
B: You could also overwrite the setters of your outer control which then call the setters of the inner control in order to propagate the values.
setHead : function(oValue) {
return this.getAggregation("_myHiddenInnerControl").setValue(oValue);
}
It is still necessary to add the inner control to an aggregation, to avoid memory leaks (else you have to make sure everything is cleaned up in the exit method.
I am trying to connect to a third party service using Breeze with a custom JsonResultsAdapter.
The third party service has the "metadata" related to an entity in the root node of the array, then the variables are in a "data" property on the "metadata" object.
The format has two ways of defining relationships. One is via a "#ref" field which references the id of another entity. The other is by having the related object defined inline (instead of the "#ref") which does not have an explicit id, but which is only ever referenced by the "parent" object.
The data looks like:
[{
"id" : "abc",
"type" : "foo",
"data": { "relationshipRef" : { "#ref" : "someid" } }
},
{
"id": "someid",
"type" : "bar",
"data" : { "relationshipInline" : { "type" : "baz",
"data" : { "something" : "whatever",
"innerRelation" : { "#ref" : "abc"}
}
}
}]
I'm currently (in JsonResultsAdapter's visitNode function) moving the properties in the "data" object up into the "root" node, and then replacing any object with an "#ref" property with the value of the "#ref" key and appending an ID to the end (so that relationships can use the original name in the EntityType). IE, the first object would become:
{
"id" : "abc",
"type" : "foo",
"relationshipRefID" : "someid"
}
This works for top level entities and relationships, but I'm having problems with the nested ones.
How would you approach solving this problem?
I was going to use ComplexTypes but the documentation mentioned that they cannot have "navigationProperties" (relationships), which as you can see above is required (the "innerRelation" property).
In some cases, the entities can be nested down to 3 levels or so.
Here is my current visitNode function:
visitNode: function(node, parseContext, nodeContext) {
if(node instanceof Object && node.type != null) {
if(node.deleted) {
//TODO: make sure the object is removed from the manager
return {ignore:true};
}
//We need to tweak the data structure to fit what breeze expects.
//It expects properties to be in the same level as the "metadata" for an object ("type" etc),
//So we need to move the properties from the data object into the node, and fix up relationships.
if(parseContext.entityManager.metadataStore.getEntityType(node.type, true) != null) {
var data = node.data;
for(var key in data) {
var prop = data[key];
//Move any foreign key fields to be "relationID":id instead of "relation":{"#ref":id}
if(prop instanceof Object) {
var ref = prop["#ref"];
if(ref != null) {
node[key+"ID"] = ref
data[key] = null;
continue;
}
}
//TODO: Handle inline references <- This is where I need help!
node[key] = data[key];
}
return {
entityType: node.type,
nodeId: node.id
}
}
else {
return {ignore:true};
}
}
}
Well, apparently I should have tested more before asking here.
It turns out that this works automatically based on the navigationProperties defined in the model! Awesome. I did have to generate ids for the inner nodes that did not have them, but that was simple.