Experimental Helpers

Warning

Experimental features are unstable. The API may change between versions without notice. Do not rely on them in production code.

Enable the Feature

mevy = { version = "0.3", features = ["0.18", "experimental"] }

These helpers are useful for prototyping and daily development. They solve common patterns with minimal syntax, but since they’re experimental, their behavior may change.

Alternative Entity Macros

Shorthand versions of entity!{} for specific world types. These are always available (no feature flag needed):

`cen![]` — Commands Entity

cen![..]     // spawn a `me: Entity`
cen![&..]    // edit a `me: Entity`
cen![*..]    // edit a `world: EntityCommands`
cen![#Marker|..]  // entity target becomes 'Marker' (named entity, not component query)

`den![]` — DeferredWorld Entity

den![..]     // spawn a `me: Entity`
den![&..]    // edit a `me: Entity`
den![*..]    // edit a `world: EntityCommands`
den![#Marker|..]  // entity target becomes 'Marker' (named entity, not component query)

`wen![]` — World Entity

wen![..]     // spawn a `me: Entity`
wen![&..]    // edit a `me: Entity`
wen![*..]    // edit a `world: EntityWorldMut`
wen![#Marker|..]  // entity target becomes 'Marker' (named entity, not component query)

The prefix indicates the world type: c = Commands, d = DeferredWorld, w = World. The & prefix before the content selects a specific entity to modify.

Warning

The # prefix in cen![#Marker|..] is consumed by the macro and does not trigger a component query. The entity target becomes the named entity Marker, not a component selector.

`modify!{}` — Entity Modification Shortcut

modify!{...} is a shorthand for entity!{<|> ...} — it always targets a specific entity via me: Entity:

modify!{
    Transform!;
    BackgroundColor(#ff0000);
}

Use this when you have an Entity variable named me and want to modify it quickly.

Get Resource — `gere![]`

Note

Requires the experimental feature flag.

// Get (immutable)
let time = gere![Time].unwrap();

// Get (mutable)
let mut time = gere![mut Time].unwrap();

// With auto .unwrap()
let time = gere![Time!];

The mut keyword before the type requests a mutable reference. The ! suffix (after the type) adds .unwrap() automatically.

Edit Resource — `edre![]`

Note

Requires the experimental feature flag.

Quickly edit a resource field:

edre![Time.delta = 0.016];

This is equivalent to:

if let Some(mut data) = world.get_resource_mut::<Time>() {
    data.delta = 0.016;
}

Get Component — `geco![]`

Note

Requires the experimental feature flag.

// Get (immutable)
let val = geco![MyComponent].unwrap();

// Get (mutable)
let mut val = geco![mut MyComponent].unwrap();

// Get (cloned)
let val = geco![MyComponent*].unwrap();

// Check existence
if geco![MyComponent?] {
    // component exists
}

// With auto .unwrap()
let val = geco![MyComponent!];

The suffixes modify behavior:

mut before the type → mutable reference
* after the type → cloned value
? after the type → returns bool (true if component exists)
! after the type → adds .unwrap() automatically

Edit Component — `edco![]`

Note

Requires the experimental feature flag.

Quickly edit a component field:

edco![MyComponent.field = 100];

This is equivalent to:

if let Some(mut data) = world.get_mut::<MyComponent>(me) {
    data.field = 100;
}

Deref Component

Prefix with * to dereference:

edco![*MyComponent.field = 100];

This dereferences the component before accessing the field, useful for Option<T> or Box<T> components.

Keyboard shortcuts

mevy