The composite contract pattern

Intent

Reusing a generic smart contract by wrapping the generic smart contract within another smart contract that configures the generic smart contract.

Consequences

Separation of concerns: the sole responsibility of the wrapper smart contract is to configure the wrapped smart contract. The sole responsibility of the wrapped smart contract is to hold the generic core functionality.
Reusability: the wrapped smart contract that supports the core functionality must only be written once. It can then be reused by different kinds of wrapper smart contracts that configure this wrapped smart contract in different ways.

Structure

Participants

Creator: the entity that starts an instance of the smart contract.
Counterparty: the entity that wants to trade with the creator.

Implementation

const start = zcf => {
    const zoe = zcf.getZoeService();
    const startInstanceOfWrappedContract = ({
      installationWrappedContract,
      /*other parameters*/
    }) => {
      const issuerKeywordRecord = harden({/*issuer keywords*/});
      //...
      return E(zoe).startInstance(
        installationWrappedContract,
        issuerKeywordRecord,
        /*terms*/
      );
    };
    const creatorFacet = Far('creatorFacet', {
      startInstanceOfWrappedContract
    });
    return harden({ creatorFacet });
  };
  harden(start);
  export { start };

The composite pattern consists of 2 smart contracts: an outer smart contract called the wrapper smart contract, and an inner smart contract called the wrapped smart contract. The wrapped smart contract is a generic smart contract that is to be configured. The wrapper smart contract starts an instance of the wrapped smart contract and configures this wrapped smart contract. The wrapper smart contract then returns the objects returned by the wrapped smart contract.

Known uses

The mint and sell NFTs smart contract.
The Over The Counter desk smart contract.
The loan smart contract.