How to access the key of the newData server variable? - firebase

Question

(Please see revised question and comment if further clarity is necessary)
Given this data structure
{
"-KWz2G9JKtwqt5Kn-pL7":true
}
How can I access the first value ( "-KWz2G9JKtwqt5Kn-pL7" ) from within the Firebase Validation Rules when I try to validate the newData?
Below please find my original question.
Background
Samples online show that the best way to connect Firebase entities is using an index where one collects id's that relate one entity within a node of another entity.
for example;
"groups":{
...
"members":{
"userid-1":true,
"userid-2":true
}
}
I want to publish an index to a node below another entity (queues/queue/tasks) with the following data structure and to validate that data structure with the set of rules described below:
{
"-KWz2G9JKtwqt5Kn-pL7":true
}
The data structure is a reference to a task entity (/tasks/task/tid) that I want to associate with a node of a separate entity.
I'm planning on putting those values into a Dictionary and adding it via setValue. When I do this Firebase should apply a validation rule. I want to verify that the identifier is one that exists elsewhere in the database.
My Index Will Look Like This
(where the identifiers relate to a set of task id's stored in another location)
"queues":{
....
"K24395498054-p23"{
"tasks": {
"-KWz2G9JKtwqt5Kn-pL7":true,
"-KWjewrkstwqt7Ln-pL3":true,
"-KWjewgqjdsllfsn-pL5":true
}
}
}
But I'm unclear on how to unpack the first value of the newData server variable within the rules when in this case, I have no child identifier.
Instead of sending a singular value, I am sending a dictionary to Firebase.
newData in this case should equal:
{
"-KWz2G9JKtwqt5Kn-pL7":true
}
Nota Bene - An interesting side note on this; I'm trying to create an
index but reading the setValue documentation. It states that the value
would be overwritten. How then can I save the dictionary without
overwriting the existing values?
Rules:
{
"rules": {
".read": "auth != null",
"queues": {
".write":"auth.provider != 'anonymous'",
"$qid": {
"members" : {
//unsure how to access the first value of the newData object without it having a label but the following shows what I am trying to accomplish
".validate":"root.child('tasks').hasChild('-KWz2G9JKtwqt5Kn-pL7')",
}
}
}
}
}
In this case I am confirming that the newData being added is a valid unique identifier that already exists as a task. In this rule the task will be associated with the queue entity.
If it helps please see my entity map below:
Alternatively
How can I create an index similar to what I am seeing online in your samples?:
To represent a set of groups that I might associate with a user....
"user_0" : {
....
"groups" : {
"group_id0":true,
"group_id1":true,
"group_id2":true
}
}
Following that, how can I validate that a group_id# actually exists under my group node elsewhere?
If I can get that answer, I may be able to extrapolate for my needs.
Update
Based on the accepted answer, I have been able to successfully apply the following rules to achieve the desired outcomes:
{
"rules": {
".read": "false",
".write": "(auth.provider != 'anonymous') && (auth != null)",
"presence": {
".read": "(auth.provider != 'anonymous') && (auth != null)",
".write": "(auth.provider != 'anonymous') && (auth != null)",
},
"queues": {
".read":"(auth != null)",
".write": "(auth.provider != 'anonymous') && (auth != null)",
"$qid": {
"tasks": {
"$taskid": {
".validate": "root.child('tasks').child($taskid).exists()"
}
}
}
},
"tasks": {
".read": "(auth != null)",
".write": "(auth.provider != 'anonymous') && (auth != null)",
"$taskid":{
"queues":{
"$qid": {
".validate":"root.child('queues').child($qid).exists()"
}
}
}
},
"users": {
".read": "(auth != null)",
".write": "(auth != null)",
"$userid":{
"groups":{
"$gid": {
".validate":"root.child('groups').child($gid).exists()"
}
},
"roles":{
"$rid": {
".validate":"root.child('roles').child($rid).exists()"
}
},
"metadata":{
".read": "(auth != null)",
".write": "(auth.provider != 'anonymous') && (auth != null)",
}
}
},
"roles": {
".read": "(auth != null)",
".write": "(auth != null)",
},
"groups":{
".read": "(auth != null)",
".write": "(auth != null)",
},
} //eof-rules
}

Answer 1

You need to add another level to your rules so that you can use a $ variable for the task ID:
{
"rules": {
".read": "auth != null",
"queues": {
".write": "auth.provider != 'anonymous'",
"$qid": {
"members": {
"$taskid": {
".validate": "root.child('tasks').hasChild($taskid)"
}
}
}
}
}
}
You can then use either set or update to add the task ID to the index:
firebase
.database()
.ref("queues/K24395498054-p23/members/-KWz2G9JKtwqt5Kn-pL7")
.set(true);
firebase
.database()
.ref("queues/K24395498054-p23/members")
.update({ "-KWz2G9JKtwqt5Kn-pL7": true });