A library for writing Substreams handlers.
Substreams consists of a number of modules which provide structs 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 the 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 must always return a Result- The Result must have an Error type set to
substreams::error:Error
use substreams::{errors::Error, store};
# mod eth { pub type Block = (); }
# mod pb { pub type Custom = (); } // holding all codegen'd protobuf structs
/// Map handler which takes a source as input
#[substreams::handlers::map]
fn map_transfers(blk: eth::Block) -> Result<pb::Custom, Error> {
unimplemented!("do something");
}
/// Map handler which takes a source, and a store in get mode as inputs
#[substreams::handlers::map]
fn map_ownerships(blk: eth::Block, mythings: store::StoreGet) -> Result<pb::Custom, Error> {
unimplemented!("do something");
}
/// Map handler which takes a source, another map, and a store in get mode as inputs
#[substreams::handlers::map]
fn map_mints(blk: eth::Block, mints: pb::Custom, mythings: store::StoreGet) -> Result<pb::Custom, Error> {
unimplemented!("do something");
}
/// Map handler which takes a source, another map, and a store in delta mode as inputs
#[substreams::handlers::map]
fn map_db(blk: eth::Block, mints: pb::Custom, store_deltas: store::Deltas) -> Result<pb::Custom, Error> {
unimplemented!("do something");
}
Below are a few store handler examples. The signature of the handler function is based
on the inputs defined in the store 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 must return nothing
use substreams::store;
# mod pb { pub type Custom = (); }
#[substreams::handlers::store]
fn store_transfers(objects: pb::Custom, output: store::StoreAddInt64) {
// to something
}
#[substreams::handlers::store]
fn store_ownerships(objects: pb::Custom, store: store::StoreGet, output: store::StoreAddInt64) {
// to something
}
#[substreams::handlers::store]
fn store_mints(objects: pb::Custom, store: store::StoreGet, another_store: store::StoreGet, store_deltas: store::Deltas, output: store::StoreAddInt64) {
// to something
}