com.r3corda.core.contracts / Contract

# Contract

`interface Contract`

Implemented by a program that implements business logic on the shared ledger. All participants run this code for every LedgerTransaction they see on the network, for every input and output state. All contracts must accept the transaction for it to be accepted: failure of any aborts the entire thing. The time is taken from a trusted timestamp attached to the transaction itself i.e. it is NOT necessarily the current time.

### Properties

legalContractReference | `abstract val legalContractReference: SecureHash` Unparsed reference to the natural language contract that this code is supposed to express (usually a hash of the contracts contents).

### Functions

verify | `abstract fun verify(tx: TransactionForContract): Unit` Takes an object that represents a state transition, and ensures the inputs/outputs/commands make sense. Must throw an exception if theres a problem that should prevent state transition. Takes a single object rather than an argument so that additional data can be added without breaking binary compatibility with existing contract code.

### Inheritors

AlwaysSucceedContract | `class AlwaysSucceedContract : Contract`
ClauseVerifier | `abstract class ClauseVerifier : Contract` Abstract superclass for clause-based contracts to extend, which provides a verify() function that delegates to the supplied list of clauses.
CommercialPaperLegacy | `class CommercialPaperLegacy : Contract`
DummyContract | `class DummyContract : Contract`