Crate substreams

Expand description

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 map module function `map_<your_action>’
map module function must always return a Result
The Result must have an Error type set to substreams::error:Error

 use substreams::{errors::Error, store};
 use substreams::store::{DeltaBigDecimal, StoreGetProto, StoreGet};
   }

 /// 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, my_things: StoreGetProto<pb::Pairs>) -> 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, myt_things: StoreGetProto<pb::Pairs>) -> 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<DeltaBigDecimal>) -> 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 map module function `store_<your_action>’
store module function must return nothing

use substreams::store;
use substreams::store::{DeltaBigDecimal, StoreGetProto, StoreAddInt64, StoreGet};

#[substreams::handlers::store]
fn store_transfers(objects: pb::Custom, output: StoreAddInt64) {
    // to something
}

#[substreams::handlers::store]
fn store_ownerships(objects: pb::Custom, store: StoreGetProto<pb::Pairs>, output: StoreAddInt64) {
    // to something
}

#[substreams::handlers::store]
fn store_mints(objects: pb::Custom, store: StoreGetProto<pb::Pairs>, another_store: StoreGetProto<pb::Tokens>, store_deltas: store::Deltas<DeltaBigDecimal>, output: StoreAddInt64) {
    // to something
}