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Cells

ReadCell[T] defers reading a dependency until get() is called:

from inlay import ReadCell

def make_service(config: ReadCell[Config]) -> Service:
    return Service(config)

The read is live. Dynamic targets are recomputed on each call, while static targets return their stored value. A cell cannot read its target while that target is still being constructed.

Cell[T] adds set(value):

from inlay import Cell

class Root(Protocol):
    config: Cell[Config]

root.config.set(new_config)
assert root.config.get() is new_config

Setting a cell updates the target and invalidates cached values that depend on it. Static computed values, fields, and execution inputs can be cell targets. Dynamic values can only be read through ReadCell.

Static policies​

Constructor and init rules default to static_policy='always'. Custom rule graphs can select:

  • 'always': the result has stable writable storage;
  • 'never': the result is dynamic;
  • 'if_static_dependencies': the result is static only when its eager dependencies are static.

A ReadCell dependency does not make an if_static_dependencies result dynamic because it is a handle rather than an eager value.

Aggregates​

Synthesized Protocol and TypedDict objects are dynamic aggregates and cannot be replaced as whole Cell targets. Their individual writable members remain assignable through the generated proxy or dictionary.