--- title: Slots url: https://citry.dev/reference/slots/ description: "The slot value and fill types." --- # Slots The slot value and fill types.
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Slot class

Bases: Generic

Normalized slot content: a lazy, repeatable, standalone callable.

Construct it from a string, a function, a CitryElement, a ComponentLike, or a CitryRender. Calling the Slot returns a render part; str(slot) renders and serializes in one step. A standalone Slot containing a ComponentLike cannot resolve without an active component render.

Example

::

Slot("Hello!")                                # static content
Slot(lambda ctx: f"Hi {ctx.data.name}!")   # content function
Slot(Card(title="Hi"))                        # composed element
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contents attribute

The original value the Slot was created from.

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component_name attribute

Name of the component this slot content was given to (for debugging).

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slot_name attribute

Name of the slot this content fills (for debugging).

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source_position attribute

The (start, end) span of the <c-fill> in its template, if any.

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extra attribute 

extra: dict[str, Any]

Scratch space for extensions to attach per-slot metadata.

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content_func attribute 

content_func: SlotFunc[TSlotData]

The content function. Call the Slot itself instead of calling this directly.

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SlotContext class

Bases: Generic

The single argument a slot function receives.

Example

::

def my_slot(ctx: SlotContext) -> str:
    return f"Hello, {ctx.data.name}!"
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data attribute 

data: TSlotData

Data passed to the slot by the <c-slot> tag (its extra attributes), or by the caller when the Slot is invoked directly. At runtime this is an immutable SlotData; the type parameter may describe a more precise component-specific field shape.

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fallback attribute 

fallback: Slot | None

The slot's fallback content (the body of the <c-slot> tag), as a Slot.

None when the Slot is called directly, outside a <c-slot> site. Coerce it to a string (or render it via {{ fallback }}) to render the fallback.

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provides attribute 

provides: Mapping[str, Any] | None

The provide/inject entries active where the Slot was invoked (the <c-slot> site or expression site). None when the Slot is called directly, outside a render. Template-defined fills use this so their bodies render with the invoking site's provides; a slot function may read it to inspect provided data.

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SlotData class

Bases: Mapping

Immutable data passed from a slot outlet to its fill.

Identifier-like keys are available as attributes, while every key remains available through mapping access. Keys beginning with an underscore and keys that collide with mapping methods intentionally require bracket access or fill-data destructuring.

Example

::

data = SlotData({"label": "Save", "aria-label": "Save item"})
data.label
data["aria-label"]

Parameters

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SlotFunc class

Bases: Protocol

The signature of a slot content function.

Example

::

def header(ctx: SlotContext) -> str:
    if ctx.data.get("name"):
        return f"Hello, {ctx.data.name}!"
    return str(ctx.fallback)
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SlotInput attribute

All forms in which slot content can be passed to a component.

Use this to type the fields of a component's Slots class::

class Table(Component):
    class Slots:
        header: SlotInput
        footer: SlotInput[FooterSlotData]

A field without a default must be filled whenever the component is used. A field annotated as SlotInput | None with a None default is optional. The required attribute on <c-slot> checks something different: it raises an error only if Citry renders that tag without content.

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SlotResult attribute

What a slot function may return.

A plain str is escaped when the slot renders; Markup or a CitryRender is trusted and inlined as-is. A ComponentLike resolves against the Citry instance rendering the slot.