StateObject

Artifact: androidx.compose.runtime:runtime

Added in 1.0.0

Cmn
```
interface StateObject
```

Known direct subclasses

NavBackStack, SnapshotStateList, SnapshotStateMap, SnapshotStateSet

`NavBackStack`	A mutable back stack of `NavKey` elements that integrates with Compose state.
`SnapshotStateList`	An implementation of `MutableList` that can be observed and snapshot.
`SnapshotStateMap`	An implementation of `MutableMap` that can be observed and snapshot.
`SnapshotStateSet`	An implementation of `MutableSet` that can be observed and snapshot.

Interface implemented by all snapshot aware state objects. Used by this module to maintain the state records of a state object.

Summary

Public functions
`open StateRecord?`	`mergeRecords( previous: StateRecord, current: StateRecord, applied: StateRecord )` Produce a merged state based on the conflicting state changes.	Cmn
`Unit`	`prependStateRecord(value: StateRecord)` Add a new state record to the beginning of a list.	Cmn

Public properties
`StateRecord`	`firstStateRecord` The first state record in a linked list of state records.	Cmn

Public functions

mergeRecords

Cmn

Added in 1.0.0

open fun mergeRecords(
    previous: StateRecord,
    current: StateRecord,
    applied: StateRecord
): StateRecord?

Produce a merged state based on the conflicting state changes.

This method must not modify any of the records received and should treat the state records as immutable, even the applied record.

Parameters
`previous: StateRecord`	the state record that was used to create the `applied` record and is a state that also (though indirectly) produced the `current` record.
`current: StateRecord`	the state record of the parent snapshot or global state.
`applied: StateRecord`	the state record that is being applied of the parent snapshot or global state.

Returns

Returns
`StateRecord?`	the modified state or `null` if the values cannot be merged. If the states cannot be merged the current apply will fail. Any of the parameters can be returned as a result. If it is not one of the parameter values then it must be a new value that is created by calling `StateRecord.create` on one of the records passed and then can be modified to have the merged value before being returned. If a new record is returned `MutableSnapshot.apply` will update the internal snapshot id and call `prependStateRecord` if the record is used.

StateRecord?

the modified state or null if the values cannot be merged. If the states cannot be merged the current apply will fail. Any of the parameters can be returned as a result. If it is not one of the parameter values then it must be a new value that is created by calling StateRecord.create on one of the records passed and then can be modified to have the merged value before being returned. If a new record is returned MutableSnapshot.apply will update the internal snapshot id and call prependStateRecord if the record is used.

prependStateRecord

Cmn

Added in 1.0.0

fun prependStateRecord(value: StateRecord): Unit

Add a new state record to the beginning of a list. After this call firstStateRecord should be value.

Public properties

firstStateRecord

Cmn

Added in 1.0.0

val firstStateRecord: StateRecord

The first state record in a linked list of state records.