Substrate; Show Me The Code

Substrate; Show Me The Code 👨‍💻

Substrate; Show Me The Code 👨‍💻

Previous lecture was all about high level information; now we want to bridge that to real code.

A Word on Previous Versions

• This is a brand new lecture replacing two old ones, with more focus on rust-docs.
• Since this is the first time, I have kept the old versions around for you to look into

Cambridge-y (adj) - Overall good quality, but with rough edges or imperfections. Especially when related to PBA content.

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A Word on the Rust Exam

Two main takeaways from the previous cohort:

• Write more rust-docs, expect them to be read.
• Extensive use of type-system, to prepare you better for FRAME.

Notes:

Personally doing my best to make it hard, but reasonable, such that it prepares you best for in-depth development of Substrate.

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Interactive

• This lecture will be interactive.
• Try and learn the technique, not the specific topic.
• Try and repeat the process later.

Notes:

what I am trying to do here is to teach you how to plant a tree rather than giving you the apple.

Documentation Resources

Core

• paritytech.github.io
  • substrate crate
  • WIP: frame, cumulus and polkadot crate.
• Github
• Substrate/Polkadot StackExchange

High level

• substrate.io*
• Discord, Telegram, etc.

Exploring the substrate crate.

https://paritytech.github.io/substrate/master/substrate/index.html

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Substrate From Within

Division of substrate when seen from inside:

1. sp
2. sc
3. frame/pallet/runtime

Notes:

this should be covered

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Substrate Binaries

Notes:

alternative way is to search for [[bin]] in all toml files.

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Structure of a Binary Crate

Division of a typical substrate-based project:

1. node
   1. Contains a main.rs
   2. service.rs
   3. and more!
2. runtime
   1. Contains a /src/lib.rs ("runtime amalgamator")
3. more!

Notes:

node is client side entry point, runtime amalgamator for the runtime.

• looking at node-template, it only has the two.
• node has even more
• polkadot has even more.

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Substrate CLI

Study in the docs:

• --dev
• --chain
• --tmp, --base-path, purge-chain.

Notes:

all commands: https://paritytech.github.io/substrate/master/sc_cli/commands/index.html all args to a typical run command https://paritytech.github.io/substrate/master/sc_cli/commands/struct.RunCmd.html

But then each node can decide which subset of these it chooses, and how it implements it.

https://paritytech.github.io/substrate/master/node_template/cli/enum.Subcommand.html https://paritytech.github.io/substrate/master/node_cli/enum.Subcommand.html

• execution strategies
• database type
• logs
• RPC
• pruning
• sync modes

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Wasm Build + std feature.

• How to compile to wasm? build.rs!
• just get your std features right please!

Notes:

https://crates.io/crates/substrate-wasm-builder (seen env variables, pretty useful!) https://docs.substrate.io/build/build-process/

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Chain Specification

Notes:

raw vs not-raw

#1 Rust-Docs Tip Of All Time

• Search traits, find implementations.
• Examples: trait Block, trait Extrinsic, trait Header.

#![allow(unused)]
fn main() {
trait Config {
  type Foo: SomeTrait<Bar>
}
}

Notes:

Especially in FRAME, oftentimes you have to parameterize your pallets with a pattern like above. Simply search the trait in the rust-docs, and find the implementors!

Additional Resources! 😋

Check speaker notes (click "s" 😉)

Note:

One important concept that is important to substrate-based chains, but is somewhat missing here is chain-spec. Make sure to read up about it in the substrate docs.