How to update an array of objects with Firestore

Question

I m currently trying Firestore  and I m stuck at something very simple   updating an array  aka a subdocument     My DB structure is super simple  For example   proprietary   John Doe   sharedWith           who   first test com   when timestamp        who   another test com   when timestamp          I m trying  without success  to push new records into shareWith array of objects   I ve tried      With SET firebase firestore    collection  proprietary    doc docID   set      sharedWith     who   third test com   when  new Date             merge  true         With UPDATE firebase firestore    collection  proprietary    doc docID   update   sharedWith     who   third test com   when  new Date           None works  These queries overwrite my array   The answer might be simple  but I could nt find it

User · Answer

We can use arrayUnion     method to achive this  Try this  collectionRef doc ID  update       sharedWith  admin firestore FieldValue arrayUnion          who   quot first test com quot          when  new Date               Documentation can find here  https   firebase google com docs firestore manage-data add-data update elements in an array

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If anybody is looking for Java firestore sdk solution to add items in array field   List lt String gt  list   java util Arrays asList  A    B    Object   fieldsToUpdate   list toArray    DocumentReference docRef   getCollection   document  docId    docRef update fieldName  FieldValue arrayUnion fieldsToUpdate      To delete items from array user  FieldValue arrayRemove

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Edit 08 13 2018  There is now support for native array operations in Cloud Firestore  See Doug s answer below     There is currently no way to update a single array element  or add remove a single element  in Cloud Firestore     This code here   firebase firestore    collection  proprietary    doc docID   set      sharedWith     who   third test com   when  new Date             merge  true       This says to set the document at proprietary docID such that sharedWith      who   third test com   when  new Date     but to not affect any existing document properties   It s very similar to the update   call you provided however the set   call with create the document if it does not exist while the update   call will fail   So you have two options to achieve what you want   Option 1 - Set the whole array  Call set   with the entire contents of the array  which will require reading the current data from the DB first   If you re concerned about concurrent updates you can do all of this in a transaction   Option 2 - Use a subcollection  You could make sharedWith a subcollection of the main document  Then adding a single item would look like this   firebase firestore      collection  proprietary      doc docID     collection  sharedWith      add   who   third test com   when  new Date        Of course this comes with new limitations  You would not be able to query documents based on who they are shared with  nor would you be able to get the doc and all of the sharedWith data in a single operation

User · Answer

Other than the answers mentioned above  This will do it  Using Angular 5 and AngularFire2  or use firebase firestore   instead of this afs       say you have have the following object and       database structure as you mentioned in your post   data     who   third test com   when  new Date            othercode     addSharedWith data         const postDocRef   this afs collection  posts   doc  docID         postDocRef subscribe  post   gt              Grab the existing sharedWith Array          If post sharedWith doesn t exsit initiated with empty array       const foo      sharedWith    post sharedWith                   Grab the existing sharedWith Array       foo  sharedWith   push data             pass updated to fireStore       postsDocRef update foo            using  set   will overwrite everything           update will only update existing values            so we initiated sharedWith with empty array

User · Answer

You can use a transaction  https   firebase google com docs firestore manage-data transactions  to get the array  push onto it and then update the document       const booking     some   data         const userRef   this db collection  users   doc userId        this db runTransaction transaction   gt               This code may get re-run multiple times if there are conflicts          return transaction get userRef  then doc   gt                if   doc data   bookings                    transaction set                       bookings   booking                                    else                   const bookings   doc data   bookings                  bookings push booking                   transaction update userRef    bookings  bookings                                      then function              console log  Transaction successfully committed            catch function  error            console log  Transaction failed     error

User · Answer

Consider John Doe a document rather than a collection  Give it a collection of things and thingsSharedWithOthers  Then you can map and query John Doe s shared things in that parallel thingsSharedWithOthers collection    proprietary   John Doe  a document   things collection of John s things documents   thingsSharedWithOthers collection of John s things being shared with others    thingId        who   first test com   when timestamp       who   another test com   when timestamp   then set thingsSharedWithOthers  firebase firestore    collection  thingsSharedWithOthers    set     thingId    who   third test com   when  new Date          merge  true

User · Answer

Edit  add explanation      say you have an array you want to update your existing firestore document field with  You can use set yourData   merge  true    passing setOptions second param in set function  with  merge  true  is must in order to merge the changes instead of overwriting  here is what the official documentation says about it  An options object that configures the behavior of set   calls in DocumentReference  WriteBatch  and Transaction  These calls can be configured to perform granular merges instead of overwriting the target documents in their entirety by providing a SetOptions with merge  true   you can use this const yourNewArray     who   quot first test com quot   when timestamp   who   quot another test com quot   when timestamp         collectionRef doc docId  set          proprietary   quot jhon quot       sharedWith  firebase firestore FieldValue arrayUnion    yourNewArray            merge  true        hope this helps

User · Answer

To build on Sam Stern s answer  there is also a 3rd option which made things easier for me and that is using what Google call a Map  which is essentially a dictionary   I think a dictionary is far better for the use case you re describing  I usually use arrays for stuff that isn t really updated too much  so they are more or less static  But for stuff that gets written a lot  specifically values that need to be updated for fields that are linked to something else in the database  dictionaries prove to be much easier to maintain and work with    So for your specific case  the DB structure would look like this   proprietary   John Doe  sharedWith     whoEmail1   when  timestamp     whoEmail2   when  timestamp      This will allow you to do the following   var whoEmail    first test com    var sharedObject       sharedObject  sharedWith     whoEmail     when     new Date    sharedObject  merge     true   firebase firestore    collection  proprietary    doc docID   update sharedObject     The reason for defining the object as a variable is that using  sharedWith     whoEmail     when  directly in the set method will result in an error  at least when using it in a Node js cloud function

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Here is the latest example from the Firestore documentation   firebase firestore FieldValue ArrayUnion  var washingtonRef   db collection  cities   doc  DC        Atomically add a new region to the  regions  array field  washingtonRef update       regions  firebase firestore FieldValue arrayUnion  greater virginia           Atomically remove a region from the  regions  array field  washingtonRef update       regions  firebase firestore FieldValue arrayRemove  east coast

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addToCart docId  string  prodId  string   Promise lt void gt        return this baseAngularFirestore collection  carts   doc docId  update           products          firestore FieldValue arrayUnion               productId  prodId              qty  1

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Firestore now has two functions that allow you to update an array without re-writing the entire thing   Link  https   firebase google com docs firestore manage-data add-data  specifically https   firebase google com docs firestore manage-data add-data update elements in an array     Update elements in an array      If your document contains an array field  you can use arrayUnion   and   arrayRemove   to add and remove elements  arrayUnion   adds elements   to an array but only elements not already present  arrayRemove     removes all instances of each given element

User · Answer

If You want to Update an array in a firebase document  You can do this      var documentRef   db collection  quot Your collection name quot   doc  quot Your doc name quot        documentRef update   yourArrayName  firebase firestore FieldValue arrayUnion  quot The Value you want to enter quot

User · Answer

Sorry Late to party but Firestore solved it way back in aug 2018 so If you still looking for that here it is all issues solved with regards to arrays   https   firebase googleblog com 2018 08 better-arrays-in-cloud-firestore htmlOfficial blog post  array-contains  arrayRemove  arrayUnion for checking  removing and updating arrays  Hope it helps

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