ios - Receive limited query with custom start point -


i'm building basic chat app swift ios firebase realtime database. messages observed limit least 10. now, want implement functionality of loading earlier send messages. i'm trying achieve using function:

let query = threadref.child("messages").queryorderedbykey().querystarting(atvalue: "2").querylimited(tolast: 2)

which returns query:

(/vyhnj3nnqlseexwajatplhikizi1/messages {    = ".key";    l = 2;    sp = 2;    vf = r; })

and should give me data:

query.observesingleevent(of: .value, with: { (snap)  in

but limits query , not set start point specific position.

here firebase database structure:

messages    -kgzb3_b26cnktdglnd8      date:       senderid:       sendername:       text:     -kgzb4qip6_jqdkrwfey    -kgzb4ha0kzklzebiaxw    -kgzb577klnkohxsqo9w    -kgzb5cqivmhrmu019jf

anyone have idea on how implement feature that?

okay found way wanted. first of misunderstood way access data firebase. how query:

let indexvalue = messages.first?.firebasekey let query = messageref.queryorderedbykey().queryending(atvalue:indexvalue).querylimited(tolast: 3)

1) firebase key saved custom chat messages

2) construct query:

  • order key
  • set ending oldest message
  • limit array query desired length

then query used:

 query.observesingleevent(of: .value, with: { snapshot in     child in snapshot.children.droplast().reversed() {        let firesnap = (child as! firdatasnapshot)        //do stuff data     } })

1) query single event

2) iterate on children , needed droplast() make sure don't have duplicated messages , reverse correct order.

3) cast current child firdatasnapshot access data

since couldn't find simple example thought leave solution here incase other people running same problem.


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