I have the next JSON structure in Firebase:
{
"-KGX6kYg1NO6d9hn-8um" : {
"phase" : "A",
"timestamp" : "12-18-2015 19:43:37"
},
"-KGXOGSxa3vompZX9UO_" : {
"phase" : "B",
"timestamp" : "03-28-2016 15:28:21"
},
"-KMUvszD-vm3Nu02sofd" : {
"phase" : "A",
"timestamp" : "04-03-2014 03:57:56"
}
}
Is it possible to filter the objects by the timestamp key through a range of date?.. For example, I want to get the objects with timestamp from January 2015 to today date. If not possible, what's the better way to filter the objects by dates?... I'm developing an iOS app.
Thanks.
You can sort the snapshot data by timestamp and define a timestamp limit from which you want your data.
For example you want all data from a specific timestamp timestamp1, your reference handler should look like:
let refHandle = tableRef.queryOrderedByChild("timestamp").queryEndingAtValue("timestamp1").observeEventType(FIRDataEventType.Value, withBlock: { (snapshot) in
for item in snapshot.children {
}
})
You can also apply number of records that you want by adding queryLimitedToLast or queryLimitedToFirst like :
let refHandle = tableRef.queryOrderedByChild("timestamp").queryEndingAtValue("some_time_stamp").queryLimitedToLast(kPostLimit + 1).observeEventType(FIRDataEventType.Value, withBlock: { (snapshot) in
for item in snapshot.children {
}
})
Also, you want to have a look at the following post about common sql queries in Firebase.
Related
I don't understand how to filter the data lists
my db has the following form
{
"numbers": [0, 1, 2, 3, 4, 5],
"models": {
"random_string_key": {
"name": "model_name",
"value": "some_value"
},
"random_string_key-2": {
"name": "Name",
"value": "any value"
}
}
}
How i can get array from numbers where all values < 3?
How i can filter models and get array models where value == "some_value"?
I would like to understand what I am doing wrong
let ref = Database.database().reference()
let refNumbers = ref.child("numbers")
refNumbers
.getData(completion: { error, snapshot in
// snapshot.value == [0, 1, 2, 3, 4, 5]
// OK
})
refNumbers
.queryOrderedByValue()
.queryEnding(beforeValue: 2)
.getData(completion: { error, snapshot in
/*
error: Unable to get latest value for query FQuerySpec (path: /numbers, params: {
en = "[MIN_NAME]";
ep = 2;
i = ".value";
}), client offline with no active listeners and no matching disk cache entries
why???
*/
})
let modelsRef = ref.child("models")
modelsRef
.getData(completion: { error, snapshot in
// snapshot.value == NSDictionary
// OK
/*
[
"key": String
"value": NSDictionary
]
*/
})
modelsRef
.queryEqual(toValue: "some_value", childKey: "value")
.getData(completion: { error, snapshot in
/*
error: null
snapshot.value == nil
why???
*/
})
modelsRef
.queryOrdered(byChild: "value")
.queryEqual(toValue: "some_value")
.getData(completion: { error, snapshot in
/*
Unable to get latest value for query FQuerySpec (path: /models, params: {
ep = some_value;
i = value;
sp = some_value;
}), client offline with no active listeners and no matching disk cache entries
why???
*/
})
I tried all the options that I found on the Internet but the result is 0
Either I get all the data from the list and filter it in the app, or I get nothing
Is it possible to filter the data upon receipt?
It is a bit difficult to give you a solution to the issues you described above but I can tell you where you're going wrong.
For #1, when you do the below
...
refNumbers
.queryOrderedByValue()
.queryEnding(beforeValue: 2)
.getData(completion: { error, snapshot in
...
})
refNumbers is not an array of numbers, it is an 'object'. And queryOrderedByValue() will not work on this 'single object', neither will .queryEnding(beforeValue: 2). You either need to do what you're doing, which is to get the entire data, convert to swift native types and filter, or you need to restructure your data on the DB side.
Similarly, in-case of #2, the object modelsRef is composed of a number of objects with random keys. So, when you perform a .queryEqual(toValue: "some_value", childKey: "value") operation, it will not find the child-key named 'value'. This child key is actually a child-key for the objects that modelsRef is composed of.
So, again, either you need to get all this data, type cast to native swift types and then filter, or somehow restructure your data.
So, the answer to your question is essentially either continue what you're doing (get data to the app and filter using native swift API which may present scalability challenges later depending on the amount of data), or, restructure your data.
Example with queryStarting & queryEnding
As requested, here is what works for me.
Database design
I have an event based app, using Firebase Realtime Database, with one parent node, lets call it events for now, because the real example is mainly in German.
Under events there is one child for each event, obviously:
{
"events": {
"-L_nMRK8mzXal47IE54x": {
"endDate": 1568715118,
"lat": 48.4382387,
"lon": 10.0499972044298,
"name": "Exampletown - event",
"city": "Exampletown",
"zip": "12345",
"startDate": 1568325600,
"street": "Street 11"
},
"-L_nMRK8mzXal47IE54y": {
"endDate": 1568715118,
"lat": 49.4382387,
"lon": 10.0499972044298,
"name": "Exampletown - event 2",
"city": "Exampletown",
"zip": "12345",
"startDate": 1568325600,
"street": "Street 12"
},
}
}
Swift 4.2
Inside a method I use the following to query the database for all past events based on the current timestamp:
let ref = Database.database().reference()
let query = ref.child("events").queryOrdered(byChild: "endDate").queryStarting(atValue: diffInterval, childKey: "endDate").queryEnding(atValue: now, childKey: "endDate")
// observe single event is sufficient for my app
query.observeSingleEvent(of: .value) { (snapshot) in
if snapshot.childrenCount > 0 {
for snap in snapshot.children {
// create an object for each of the objects of the snapshot
guard let eventData = self.getEventsFromSnapshot(snap: snap as! DataSnapshot) else {return}
// do something with eventData
}
} else {
// custom logging and return of empty array
}
}
I am trying to query by name inside firebase database, I want to return all the names matching the query. But I can't seem to get it to work, I am getting error Consider adding ".indexOn": "name" at / to your security rules.
Security Rules:
{
"rules": {
".read": "true",
".write": "true",
"goals_new": {
".indexOn": ["name"]
}
}
}
I Can retrieve the names for specific child like this:
let query = ref.child("goals_new").queryOrdered(byChild:"name").queryEqual(toValue: name)
query.observe(.childAdded) { (snapshot) in
// if let values =
if let values = snapshot.value as? [String:String] {
print(values)
print(values["name"]?.count ?? "")
}
}
But I want to retrieve all the names in the database that matches the query
Database Structure:
"goals_new" : [ null, {
"name" : "Eric thomas",
"pic" : “…….”,
"title" : "Be Obsessed with your Goals",
"url" : “……”
},
{
"name" : "Bob Proctor",
"pic" : “……….",
"title" : "Goal Achievement System",
"url" : “………”
},
Any help would be appreciated.
Consider adding ".indexOn": "name" at / to your security rules <- Is only a warning so you don't have to worry much about that.
I'm seeing perhaps an error. Looks like you're using an array to store your objects of 'goals_news' because of the keys are numbers 1, 2, etc... Maybe that's is messing with your query, you have to change them for string keys like every time you add one use firebase method childByAutoID().
Better use .value instead of .childAdded method so you can get all the objects that matches the name, something like this:
let query = ref.child("goals_new").queryOrdered(byChild:"name").queryEqual(toValue: name)
query.observe(.value) { (snapshot) in
guard snapshot.exists() && snapshot.hasChildren() else {return}
for snap in snapshot.children {
var currentSnapValue = (snap as! DataSnapshot).value as! [String: String]
print("Name: \(currentSnapValue["name"])")
}
}
That way you're getting all the objects that matches the name
My database structure is some thing like this:
{
"users": {
"alovelace": {
"name": "Ada Lovelace",
"score": 4,
},
"ghopper": { ... },
"eclarke": { ... }
}
}
I am trying to retrieve top 20 scores in descending order.
let queryRef = FIRDatabase.database().reference().child("users").queryOrderedByChild("score").queryLimitedToLast(20)
queryRef.observeSingleEventOfType(.Value, withBlock: { (querySnapShot) in
print(querySnapShot.value)
})
i am trying to get output like
score": 4
score": 3
score": 2
or
score": 2
score": 3
score": 4
or
2
3
4
Please let me know how to solve this.
When you request the children in a specific order, the resulting snapshot will contain both the data that matches the query and information about the order in which you requested them.
But when you request the .value of the snapshot, the keys+data are converted to a Dictionary<String,AnyObject>. Since a dictionary does not have an extra place to put the information about the order, that information is lost when converting to a dictionary.
The solution is to not convert to a dictionary prematurely and instead loop over the snapshot:
queryRef.observeSingleEventOfType(.Value, withBlock: { (querySnapShot) in
for childSnapshot in querySnapShot.children {
print(childSnapshot.value)
}
})
You can also listen to the .ChildAdded event, instead of .Value, in which case the children will arrive in the correct value:
queryRef.observeSingleEventOfType(.ChildAdded, withBlock: { (childSnapshot) in
print(childSnapshot.value)
})
Update
I just added this JSON to my database:
{
"users" : {
"alovelace" : {
"name" : "Ada Lovelace",
"score" : 4
},
"eclarke" : {
"name" : "Emily Clarke",
"score" : 5
},
"ghopper" : {
"name" : "Grace Hopper",
"score" : 2
}
}
}
And then ran this code:
let queryRef = ref.child("users").queryOrderedByChild("score").queryLimitedToLast(20);
queryRef.observeEventType(.ChildAdded) { (snapshot) in
print(snapshot.key)
}
The output is:
ghopper
alovelace
eclarke
Which is the users in ascending order of score.
Update to add more on getting the scores in descending order
The above code gets the 20 highest scores in ascending order. There is no API call to return themthem in descending score.
But reversing 20 items client side is no performance concern, you just need to write the code for it. See for example this answer.
If you really are stuck on reversing them client side, you can add an inverted score. See this answer for an example of that.
Use method observeEventType instead of observeSingleEventOfType.
Also, make FIRDataEventType to ChildAdded.
Last, If you want Top 20 items, use queryLimitedToFirst instead of queryLimitedToLast.
{
"users" : {
"alovelace" : {
"name" : "Ada Lovelace",
"score" : 4
},
"eclarke" : {
"name" : "Emily Clarke",
"score" : 5
},
"ghopper" : {
"name" : "Grace Hopper",
"score" : 2
}
}
}
For the dataset above
let queryRef = FIRDatabase.database().reference().child("users").queryOrderedByChild("score").queryLimitedToFirst(20)
queryRef.observeEventType(.ChildAdded, withBlock: { (snapshot) in
print("key: \(snapshot.key), value: \(snapshot.value)")
})
key: ghopper, value: Optional({
name = Grace Hopper;
score = 2;
})
key: alovelace, value: Optional({
name = Ada Lovelace;
score = 4;
})
key: eclarke, value: Optional({
name = Emily Clarke;
score = 5;
})
Snapshot will returns the contents as native types.
Data types returned:
NSDictionary
NSArray
NSNumber (also includes booleans)
NSString
So, you can get your scores this way.
let queryRef = FIRDatabase.database().reference().child("users").queryOrderedByChild("score").queryLimitedToFirst(20)
queryRef.observeEventType(.ChildAdded, withBlock: { (snapshot) in
if let scores = snapshot.value as? NSDictionary {
print(scores["score"])
}
})
Optional(2)
Optional(4)
Optional(5)
Moreover, the default of realtime database return everything in ascending order.
If you want descending order, you can make some tricks(4:40) in your database.
I have a Firebase db structure as follows:
{
"listings" : {
"-KOt8OUGkUphoMyqEXJ2" : {
"created" : 1470911323208,
"ends" : 1470911323209,
"make" : "LONDON TAXIS INT",
"model" : "TX4 BRONZE",
"status" : "For Sale",
},
"-KOt97_P8sJW7woED4aH" : {
"created" : 1470911515115,
"ends" : 1471775515000,
"make" : "NISSAN",
"model" : "QASHQAI N-TEC",
"status" : "For Sale",
},
"-KOt_BYYUEaXu_LNvnUv" : {
"created" : 1470918609414,
"ends" : 1471782609000,
"make" : "MAZDA",
"model" : "3 TS",
"status" : "For Sale",
}
}
}
I use GeoFire to get keys for listings in a given radius. I then use observeSingleEventOfType to return the listing for the key. This all works fine.
However, I would like to only return a listing if the "ends" timestamp > current time. I have tried the following approach:
geoQueryHandle = geoQuery.observeEventType(.KeyEntered, withBlock: {(key, location) in
let listingRef = self.ref.child("listings").child(key)
let now = Int(NSDate().timeIntervalSince1970 * 1000)
let query = listingRef.queryStartingAtValue(now, childKey: "ends")
query.observeSingleEventOfType(.Value, withBlock: {snapshot in
if let listing = Listing(snapshot: snapshot, location: location) {
//...populate my tableview
}
}
})
Can anyone advise me on why my query isn't working?
Thanks
Firebase queries apply ordering/filtering to the properties of the child nodes of the location where you execute them.
queryLocation
child1
filterProperty: filterValue
child2
filterProperty: filterValue
Since your listingRef already points to a specific listing, the order/filter you add will apply to child nodes one level deeper.
The simplest way to get your use-case working seems to simply filter the node client-side:
let listingRef = self.ref.child("listings").child(key)
query.observeSingleEventOfType(.Value, withBlock: {snapshot in
if let listing = Listing(snapshot: snapshot, location: location) {
let now = Int(NSDate().timeIntervalSince1970 * 1000)
// TODO: exit if snapshot.child("ends").getValue() < now
//...populate my tableview
}
}
A more complex, but more efficient, way to accomplish this would be to remove the expired events from the Geofire location.
I'm using firebase to collect data, and i'm trying to retrieve the data in a usable format for an iPhone app, and i can't quite get it out properly. I'm writing the app in Swift.
The data is grouped by a date string then the with a random key and then the data. Eg:
{
"20160304" : {
"-KC-aOwSWpt4dlYmjJE4" : {
"coordinates" : "-37.7811465912404, 145.005993055861",
"event" : "Test event",
"time" : "2016-03-04 07:48:43 +0000"
}, etc...
I'm so far grabbing the data like this:
ref.queryOrderedByKey().observeEventType(.ChildAdded, withBlock: {
snapshot in
//print(snapshot.key) // date
print(snapshot.value)
})
And it returns something like this to the console:
{
"-KD8O0gL7gDGu_hRyFzQ" = {
coordinates = "-37.7540958861003, 145.001224694195";
event = "Test event";
time = "2016-03-18 11:02:32 +0000";
}; etc...
Does anyone know how i can get down to the next level, past the random keys, to the meaningful data? I had trouble before with this for javascript, but it's confusing me using swift.
I'd like to be able to grab the detailed data (bottom level) for a defined date (top level).
Try this code
let jsonLocations = snapshot.valueInExportFormat() as! NSDictionary
let keys = jsonLocations.allKeys
for key in keys {
let json = jsonLocations[key] as! [String: AnyObject]
self.sections.append(Location(JSONObject: json))
}
I usually try to stick to methods of FDatasnapshot as long as possible, which leads to:
ref.queryOrderedByKey().observeEventType(.ChildAdded, withBlock: { snapshot in
for child in snapshot.children {
print(child.key); // -KC-aOwSWpt4dlYmjJE4
print(child.childSnapshotForPath("event").value)
}
});