Struct Environment 

pub struct Environment { /* private fields */ }

An Environment stores a map of types to values.

Each type can have at most one value in the environment. The environment is used to pass contextual information from parent views to child views.

Examples

use waterui_core::Environment;

let mut env = Environment::new();
env.insert(String::from("hello"));

// Get the value back
assert_eq!(env.get::<String>(), Some(&String::from("hello")));

// Remove the value
env.remove::<String>();
assert_eq!(env.get::<String>(), None);

Implementations

impl Environment

pub fn identity(&self) -> usize

Returns a stable identity for this environment overlay chain.

pub fn new() -> Self

Creates a new empty environment.

pub fn store<K: 'static, V: 'static>(self, value: V) -> Self

Stores a value in the environment indexed by type K.

Arguments

• value - The value to store

pub fn query<K: 'static, V: 'static>(&self) -> Option<&V>

Queries for a value in the environment indexed by type K.

Returns

An optional reference to the stored value

pub fn install(&mut self, plugin: impl Plugin) -> &mut Self

Installs a plugin into the environment.

Plugins can register values or modifiers that will be available to all views.

pub fn insert<T: 'static>(&mut self, value: T)

Inserts a value into the environment.

If a value of the same type already exists, it will be replaced.

pub fn insert_hook<T: ViewConfiguration, V: View>( &mut self, hook: impl Fn(&Self, T) -> V + 'static, )

Inserts a view configuration hook into the environment.

Hooks allow you to intercept and modify view configurations globally.

pub fn remove<T: 'static>(&mut self)

Removes a value from the environment by its type.

pub fn with<T: 'static>(&mut self, value: T) -> &mut Self

Adds a value to the environment and returns the modified environment.

This is a fluent interface for chaining multiple additions.

pub fn extending<T: 'static>(&self, value: T) -> Self

Returns a new environment that overlays a value on top of the current state.

This is an O(1) operation backed by structural sharing and avoids copying the underlying map.

pub fn get<T: 'static>(&self) -> Option<&T>

Retrieves a reference to a value from the environment by its type.

Returns None if no value of the requested type exists.

Panics

This function will panic if a value of the requested type exists in the environment, but the stored value cannot be downcast to the requested type. This should never happen if only insert and with are used to add values.

pub fn get_nth<T: 'static>(&self, index: usize) -> Option<&T>

Retrieves the index-th visible value of type T, counting from the nearest (most recently overlaid) value outwards.

get_nth(0) therefore always agrees with get.

This is primarily used by action extractors to support repeated same-typed crate::extract::State values in a single handler, and nearest-first is what gives those handlers positional correspondence: .state(&a).state(&b) wraps b outermost, so b’s overlay is applied first and a ends up nearest — and a is what the first State<T> handler parameter must bind to.

pub fn get_or_insert_with<T: 'static, F: FnOnce() -> T>(&mut self, f: F) -> &T

Retrieves a reference to a value from the environment by its type, inserting a new value if it does not already exist.

The new value is created by calling the provided closure f.

Panics

Panics if insertion succeeds but the inserted value cannot be retrieved back as T, which indicates a corrupted environment entry.

pub fn extract<T: Extractor>(&self) -> Result<T, Error>

Extracts a value from the environment using the Extractor trait.

This is a convenience method for extracting values that implement Extractor.

Errors

Returns an error if extraction fails (e.g., value not found).

pub fn layered_on(&self, parent: &Self) -> Self

Replays this environment’s overlays on top of parent.

This preserves repeated same-typed overlay entries instead of collapsing them into a single visible value.

Trait Implementations

impl Clone for Environment

fn clone(&self) -> Environment

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Environment

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

Formats the value using the given formatter.

impl Default for Environment

fn default() -> Self

Returns the “default value” for a type.

impl Extractor for Environment

fn extract(env: &Environment) -> Result<Self, Error>

Extracts the Environment itself by creating a clone.

fn extract_from_action( env: &Environment, state: &mut ExtractionState, ) -> Result<Self, Error>

Attempts to extract an instance of Self from the given environment for an action handler invocation.

impl MetadataKey for Environment