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Foundations · hard

41. No inheritance: composing via interfaces and calls

How Vyper achieves modularity without base contracts.

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Instead of inheriting shared logic, Vyper contracts compose by calling out to other deployed contracts through interfaces, or by copy-adapting a well-reviewed pattern into each contract explicitly. This trades some code duplication for the guarantee that every contract's logic is fully visible in its own file.

interface Registry:
    def is_allowed(user: address) -> bool: view

registry: public(address)

@external
def restricted_action():
    assert Registry(self.registry).is_allowed(msg.sender), "not allowed"

This pattern also naturally supports upgradeable 'policy' contracts: swap the registry address and behaviour changes without touching the calling contract's code.

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  1. 1. How does Vyper share logic across contracts without inheritance?

  2. 2. What's a benefit of the 'each contract fully visible in its own file' approach?

  3. 3. What does swapping a registry contract's address enable?

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