A library for writing Substreams handlers.
Substreams consts of a numbmbder of modules that provide struct and macros for implementing Substreams handlers. The handlers are defined in your Manifest. Learn more about Substreams at https://substreams.streamingfast.io
Handler Examples
Below are a few map handler examples. The signature of then handler function is based
on the inputs and output defined in the map module definition in the Manifest. There
are a few things to note:
- Best practice is to name your
mapmodule function `map_<your_action>' mapmodule function should always return a Result- The Result should have an Error type set to
subtreams::error:Error
use substreams::{errors::Error, store};
// map handler that takes a source as input
#[substreams::handlers::map]
fn map_transfers(blk: eth::Block) -> Result<proto::Custom, Error> {
// do something
}
// map handler that takes a source, and a store in get mode as inputs
#[substreams::handlers::map]
fn map_ownerships(blk: eth::Block, store: store::StoreGet) -> Result<proto::Custom, Error> {
// do something
}
// map handler that takes a source, another map, and a store in get mode as inputs
#[substreams::handlers::map]
fn map_mints(blk: eth::Block, mints: proto::Custom, store: store::StoreGet) -> Result<proto::Custom, Error> {
// do something
}
//!
// map handler that takes a source, another map, and a store in delta mode as inputs
#[substreams::handlers::map]
fn map_db(blk: eth::Block, mints: proto::Custom, store_deltas: store::Deltas) -> Result<proto::Custom, Error> {
// do something
}
Below are a few store handler examples. The signature of the handler function is based
on the inputs defined in the stopre module definition in the Manifest. There
are a few things to note:
- Best practice is to name your
mapmodule function `store_<your_action>' storemodule function should return nothing
use substreams::store;
#[substreams::handlers::store]
fn store_transfers(objects: proto::Custom, output: store::StoreAddInt64) {
// to something
}
#[substreams::handlers::store]
fn store_ownerships(objects: proto::Custom, store: store::StoreGet, output: store::StoreAddInt64) {
// to something
}
#[substreams::handlers::store]
fn store_mints(objects: proto::Custom, store: store::StoreGet, another_store: store::StoreGet, store_deltas: store::Deltas, output: store::StoreAddInt64) {
// to something
}