Tezos support in Truffle is experimental. Give it a spin, and help us out by filing issues on Github.
Writing Tezos Contracts¶
Smart contracts in Tezos are written in the LIGO programming language. We recommend you familiarize yourself with the language before continuing. Their documentation is excellent.
Note! LIGO supports three different syntaxes out of the box: CamelLIGO, PascalLIGO, and ReasonLIGO. For all examples in this documentation, we use PascalLIGO.
Example Contract & Overview¶
All contracts within a Tezos-based Truffle project are stored in the
./contracts directory. An example contract looks like the following:
// variant defining pseudo multi-entrypoint actions
type action is
| Increment of int
| Decrement of int
function add (const a : int ; const b : int) : int is a + b
function subtract (const a : int ; const b : int) : int is a - b
// real entrypoint that re-routes the flow based on the action provided
function main (const p : action ; const s : int) : (list(operation) * int) is
((nil : list(operation)),
case p of
| Increment (n) -> add (s, n)
| Decrement (n) -> subtract (s, n)
There's some important takeaways to note when writing LIGO contracts:
- By default, all LIGO contracts have a single entry point called
main, expected by Truffle. For multiple entry points, see below.
- The last parameter to the entry point function represents the current state of the contract, and is sent to the function via the underlying protocol.
- All LIGO contracts return two things: A list of further operations the protocol should perform, and the final state of the contract after execution of the entry point.
Defining Multiple Entry Points¶
You'll notice that the comments in the example contract above suggest there are multiple entry points beyond
main(). Conceptually there are multiple entry points --
decrement -- but under the hood,
main() is technically the single entery point of the contract.
To code a contract with multiple entry points that Truffle can take advantage of, you'll need to follow the example above. Start by defining an enum-like type called
action with values relative to the functions being called, and then pass the action as the first value into
main(). As you'll see in the Interacting With Your Contracts section, if Truffle detects an
action type as the first parameter in
main(), it'll treat your contract as though it has multiple entry points, and make those entry points easy to call from outside the blockchain.
Including Other Contracts¶
Sometimes it's nice to organize your code in multiple files. Fortunately, the LIGO compiler does this for you. To do so, check out the LIGO documentation for more. You'll still need one contract that contains a
main() function, though you can organize other contract code in other files as needed.
How do I compile?¶
It's easy. See the Compiling Tezos Contracts section for more!