Saving Data on Android

Realtime Database Rules
 for authorization. Database rules allow you to control 
access for each user. They determine who has read and write access to your database,
Saving Data on Android
Chapter 12: Introduction to Firebase Realtime Database
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how your data is structured, and what indexes exist. Every time reading or writing is 
attempted, a request will only be completed if your rules allow it.
Firebase Database rules are also a 
JSON object
 which must have a top-level 
rules
 
node. By default, the rules node contains two primitives, 
.read
 and 
.write
 and they 
determine who has read and write access. If 
.read
 and 
.write
 are set to 
true
, 
everyone would have complete access to your data, so they can both read and write 
as they want. To protect your database from the abuse, you need to customize those 
rules.
The Firebase Database Rules include built-in variables and functions that allow you 
to refer to other paths, server-side timestamps, authentication information, and 
much more. For this app, you'll write a rule that grants read and write access only for 
authenticated users.
This is what this rule looks like:
{ 
  
"rules"
: { 
    
".read"
: 
"auth != null"
, 
    
".write"
: 
"auth != null"
 
  } 
}
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