Struct StateManager 

pub struct StateManager { /* private fields */ }

A helper for managing state and generating deltas.

StateManager tracks the current state and provides methods to update it while automatically computing the JSON Patch delta between states. This is useful for efficiently synchronizing state with frontends.

Example

use ag_ui_core::state::StateManager;
use serde_json::json;

let mut manager = StateManager::new(json!({"count": 0, "items": []}));

// Update state - returns delta patch
let delta = manager.update(json!({"count": 1, "items": []}));
assert!(delta.is_some());

// No change - returns None
let delta = manager.update(json!({"count": 1, "items": []}));
assert!(delta.is_none());

// Check current state
assert_eq!(manager.current()["count"], 1);

Implementations

impl StateManager

pub fn new(initial: JsonValue) -> Self

Creates a new state manager with the given initial state.

pub fn current(&self) -> &JsonValue

Returns a reference to the current state.

pub fn version(&self) -> u64

Returns the current state version (increments on each update).

pub fn update(&mut self, new_state: JsonValue) -> Option<Patch>

Updates the state and returns the delta patch if there were changes.

Returns None if the new state is identical to the current state.

pub fn update_with<F>(&mut self, f: F) -> Option<Patch>

where F: FnOnce(&mut JsonValue),

Updates the state using a closure and returns the delta patch.

The closure receives a mutable reference to the current state. After the closure completes, the delta is computed.

Example

use ag_ui_core::state::StateManager;
use serde_json::json;

let mut manager = StateManager::new(json!({"count": 0}));

let delta = manager.update_with(|state| {
    state["count"] = json!(10);
});

assert!(delta.is_some());
assert_eq!(manager.current()["count"], 10);

pub fn reset(&mut self, new_state: JsonValue)

Resets the state to a new value without computing a delta.

Use this when you want to replace the entire state (e.g., on reconnection) and will send a snapshot instead of a delta.

pub fn snapshot(&self) -> JsonValue

Takes a snapshot of the current state.

Returns a clone of the current state value.

Trait Implementations

impl Clone for StateManager

fn clone(&self) -> StateManager

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for StateManager

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for StateManager

fn default() -> Self

Returns the “default value” for a type.