Interface Patterns

importlib.enforce_interface(...) lets a contract validate another contract's shape before using it. The first argument can be either an imported contract module or a contract name string.

Example

token = importlib.import_module("con_token")

ok = importlib.enforce_interface(
    token,
    [
        importlib.Func("transfer", args=("amount", "to")),
        importlib.Var("balances", Hash),
    ],
)

assert ok, "Token does not satisfy the expected interface"

If you do not need the module object for anything else, you can pass the contract name directly:

ok = importlib.enforce_interface(
    "con_token",
    [
        importlib.Func("transfer", args=("amount", "to")),
        importlib.Var("balances", Hash),
    ],
)

Variable Markers

Use the storage type name itself as the second argument to importlib.Var. Do not quote it and do not pass a constructed storage object.

Supported storage markers are:

Marker	Interface requirement
Variable	local Variable storage
Hash	local Hash storage
ForeignVariable	foreign Variable storage
ForeignHash	foreign Hash storage

The compiler preserves these markers in the Xian VM artifact, and the runtime resolves them as interface type markers when the contract executes.

Why It Matters

This is the closest thing to interface checking in the contract runtime. It is especially useful for dynamic imports and contract-standard enforcement.