Service

Smart Contract Service#

When writing a smart contract in aelf, the first step is to define it so our tools can generate it. aelf contracts are defined and generated using gRPC and protobuf.

Example: Multi-Token Contract#

Here is a simplified part of our multi-token contract definition:

1syntax = "proto3";
2
3package token;
4option csharp_namespace = "AElf.Contracts.MultiToken.Messages";
5
6service TokenContract {
7    option (aelf.csharp_state) = "AElf.Contracts.MultiToken.TokenContractState";
8
9    // Actions
10    rpc Create (CreateInput) returns (google.protobuf.Empty) { }
11    rpc Transfer (TransferInput) returns (google.protobuf.Empty) { }
12
13    // Views
14    rpc GetBalance (GetBalanceInput) returns (GetBalanceOutput) {
15        option (aelf.is_view) = true;
16    }
17}

Service Methods#

There are two types of methods in a service:

Actions#

These methods take input and output protobuf messages.

They usually modify the state of the chain.

Example:

1rpc Create (CreateInput) returns (google.protobuf.Empty) { }

Takes a protobuf message as input and returns a protobuf message.

google.protobuf.Empty signifies returning nothing.

Convention: append Input to protobuf types used as parameters.

Views#

These methods do not modify the state of the chain.

They are used to query the state.

Example:

1rpc GetBalance (GetBalanceInput) returns (GetBalanceOutput) {
2    option (aelf.is_view) = true;
3}

Annotated with a view option to indicate it's read-only.

Edited on: 15 July 2024 03:24:10 GMT+0