IMPORTANT: In July 2025, we stopped releasing new versions of KTX modules, and we removed the KTX libraries from the Firebase Android BoM (v34.0.0). If you use KTX APIs from the previously released KTX modules, we recommend that you migrate your app to use KTX APIs from the main modules instead. For details, see the FAQ about this initiative.

MutableData

class MutableData

Instances of this class encapsulate the data and priority at a location. It is used in transactions, and it is intended to be inspected and then updated to the desired data at that location. Note that changes made to a child MutableData instance will be visible to the parent and vice versa.

Summary

Public functions
`MutableData`	`child(path: String)` Used to obtain a MutableData instance that encapsulates the data and priority at the given relative path.
`Boolean`	`equals(o: Any!)`
`(Mutable)Iterable<MutableData!>`	`getChildren()` Used to iterate over the immediate children at this location
`Long`	`getChildrenCount()`
`String?`	`getKey()`
`Any?`	`getPriority()` Gets the current priority at this location.
`Any?`	`getValue()` getValue() returns the data contained in this instance as native types.
`T?`	`<T> getValue(t: GenericTypeIndicator<T!>)` Due to the way that Java implements generics, it takes an extra step to get back a properly-typed Collection.
`T?`	`<T> getValue(valueType: Class<T!>)` This method is used to marshall the data contained in this instance into a class of your choosing.
`Boolean`	`hasChild(path: String)`
`Boolean`	`hasChildren()`
`Unit`	`setPriority(priority: Any?)` Sets the priority at this location
`Unit`	`setValue(value: Any?)` Set the data at this location to the given value.
`String!`	`toString()`

Extension functions
`inline T?`	`<T : Any?> MutableData.getValue()` Returns the content of the MutableData converted to a POJO.

Public functions

child

fun child(path: String): MutableData

Used to obtain a MutableData instance that encapsulates the data and priority at the given relative path.

Parameters
`path: String`	A relative path

Returns
`MutableData`	An instance encapsulating the data and priority at the given path

equals

fun equals(o: Any!): Boolean

getChildren

fun getChildren(): (Mutable)Iterable<MutableData!>

Used to iterate over the immediate children at this location

    for (MutableData child : parent.getChildren()) {
            ...
    }

Returns
`(Mutable)Iterable<MutableData!>`	The immediate children at this location

getChildrenCount

fun getChildrenCount(): Long

Returns
`Long`	The number of immediate children at this location

getKey

fun getKey(): String?

Returns
`String?`	The key name of this location, or null if it is the top-most location

getPriority

fun getPriority(): Any?

Gets the current priority at this location. The possible return types are:

Double
String

Note that null is allowed

Returns
`Any?`	The priority at this location as a native type or null if no priority was set

getValue

fun getValue(): Any?

getValue() returns the data contained in this instance as native types. The possible types returned are:

Boolean
Long
Double
String
Map<String, Object>
List<Object>

This list is recursive; the possible types for java.lang.Object in the above list is given by the same list. These types correspond to the types available in JSON.

Returns
`Any?`	The data contained in this instance as native types, or null if there is no data at this location.

getValue

fun <T> getValue(t: GenericTypeIndicator<T!>): T?

Due to the way that Java implements generics, it takes an extra step to get back a properly-typed Collection. So, in the case where you want a java.util.List of Message instances, you will need to do something like the following:

    GenericTypeIndicator<List<Message>> t =
        new GenericTypeIndicator<List<Message>>() {};
    List<Message> messages = mutableData.getValue(t);

It is important to use a subclass of GenericTypeIndicator. See GenericTypeIndicator for more details

Parameters
`<T>`	The type to return. Implicitly defined from the `GenericTypeIndicator` passed in
`t: GenericTypeIndicator<T!>`	A subclass of `GenericTypeIndicator` indicating the type of generic collection to be returned.

Returns
`T?`	A properly typed collection, populated with the data from this instance, or null if there is no data at this location.

getValue

fun <T> getValue(valueType: Class<T!>): T?

This method is used to marshall the data contained in this instance into a class of your choosing. The class must fit 2 simple constraints:

The class must have a default constructor that takes no arguments
The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized

An example class might look like:

    class Message {
        private String author;
        private String text;

        private Message() {}

        public Message(String author, String text) {
            this.author = author;
            this.text = text;
        }

        public String getAuthor() {
            return author;
        }

        public String getText() {
            return text;
        }
    }


    // Later
    Message m = mutableData.getValue(Message.class);

Parameters
`<T>`	The type to return. Implicitly defined from the class passed in
`valueType: Class<T!>`	The class into which this data in this instance should be marshalled

Returns
`T?`	An instance of the class passed in, populated with the data from this instance, or null if there is no data at this location.

hasChild

fun hasChild(path: String): Boolean

Parameters
`path: String`	A relative path

Returns
`Boolean`	True if data exists at the given path, otherwise false

hasChildren

fun hasChildren(): Boolean

Returns
`Boolean`	True if the data at this location has children, false otherwise

setPriority

fun setPriority(priority: Any?): Unit

Sets the priority at this location

Parameters
`priority: Any?`	The desired priority or null to clear the existing priority

setValue

fun setValue(value: Any?): Unit

Set the data at this location to the given value. The native types accepted by this method for the value correspond to the JSON types:

Boolean
Long
Double
Map<String, Object>
List<Object>

In addition, you can set instances of your own class into this location, provided they satisfy the following constraints:

The class must have a default constructor that takes no arguments
The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized

Generic collections of objects that satisfy the above constraints are also permitted, i.e. Map<String, MyPOJO>, as well as null values.

Note that this overrides the priority, which must be set separately.

Parameters
`value: Any?`	The value to set at this location or null to delete the existing data

Throws
`com.google.firebase.database.DatabaseException: com.google.firebase.database.DatabaseException`

toString

fun toString(): String!

Extension functions

getValue

inline fun <T : Any?> MutableData.getValue(): T?

Returns the content of the MutableData converted to a POJO.

Supports generics like List<> or Map<>. Use @JvmSuppressWildcards to force the compiler to use the type T, and not ? extends T.