ios firebase how to fetch multiple object inside collection? - ios

Question

I had a problem with firebase , i have 5 document IDs . I need to query those 5 documents , convert them in to object.
for oneID in allIDs {
self.db.collection("storecollection").document(oneID).getDocument {(snap,err) in
let oneobject = convertToObject(snap)
self.tempHolder.append(oneobject)
var newarray = [MyObjectClass]()
if allIDs.last == oneID {
// perform copy
for x in 0...(self.tempHolder.count -1){
newarray.append(self.tempHolder[x])
}
self.tempHolder.removeAll()
completion(newarray)
}
}
Something wrong with code above , the size of self.tempHolder always count = 1. (Only the last id fetched object exist) i have no idea how to make it right.
Whats the right way to fetch multiple document (with specifiedID) ???

Answer 1

There's a bit of extraneous code in the question so it's not exactly clear but it seems you want to iterate over an array of document keys, read each associated document and add properties to an array (or in your case create an object based on those properties and add it)
Here's a simple example reading in a series of posts, and appending the post text from each post in an array.
The structure is
posts //a collection
post_0
post_text: "A post"
post_1
post_text: "Another post"
post_2
post_text: "Cool post"
and the code to read in post_0 and post_2 and append the post text to an array
var postTextArray = [String]()
func readMultiplePosts() {
let postKeyArray = ["post_0", "post_2"]
for postKey in postKeyArray {
let docRef = self.db.collection("posts").document(postKey)
docRef.addSnapshotListener { documentSnapshot, error in
guard let document = documentSnapshot else {
print("err fetchibng document")
return
}
guard let data = document.data() else {
print("doc was empty")
return
}
print("doc data: \(data)")
let post = document.get("post_text") as! String
self.postMsgArray.append(post)
}
}
}
then sometime later we want to print the post texts
for p in self.postMsgArray {
print(p)
}
and the output from console
A post
Cool post
While this solution works, a Firebaser will quickly point out that reading data like this in a tight loop is generally not recommended. It would be better to have some other correlation between the posts you want to read and then perform a query to read them in.