Canton Daml Interfaces

Overview

An interface defines an abstract type plus a behavior — a view type, method signatures, and choices. A template conforms to it via an interface instance that implements every method (including the special view). This decouples behavior from implementation, so other developers write apps against the interface instead of your concrete template. Interfaces are how Canton achieves cross-app interoperability — the Token Standard and dApp Standard are sets of interfaces.

Requirements: Daml-LF 1.15+ (current default) and, on Canton, sync-domain protocol version 4+.

Declaring an interface

interface MyInterface where
  viewtype MyInterfaceViewType            -- required; a record returned by interface subscriptions

  method1 : Party                          -- method signatures (lowercase names)
  method2 : Int
  method3 : Bool -> Int -> Int -> Int