Make legacy code delightful with statecharts

Matt Pocock

Legacy code is everywhere

Legacy code is code without an organisational advocate

When you understand the intent of legacy code, it stops being legacy

Legacy Code in React

useEffect

Let's look at some code

What's wrong with this process?

You need to track all the dependencies first

Then, understand all the implementation details

The intent of the code is the last thing you understand

Is this process delightful?

Let's go again!

mattpocock/react-finland-talk

This problem scales with complexity

How would you mitigate it?

Inline Comments

External Docs

Abstractions

What's the solution?

Statecharts

Intent first, implementation second

Explicit events > Implicit dependencies

Tired: the diagram represents the code

Wired: the diagram is the code

Statically Analyzable Code

Code that can speak for itself

Thank you!

interface PokemonFetcherProps {
  id: string;
}

const PokemonFetcher = (props: PokemonFetcherProps) => {
  const [pokemonData, setPokemonData] = useState();
  const [typeData, setPokemonTypeData] = useState();

  useEffect(() => {
    if (pokemonData) {
      fetchPokemonType(pokemonData.typeId).then((data) => {
        setPokemonTypeData(data);
      });
    }
  }, [pokemonData]);

  useEffect(() => {
    fetchPokemon(props.id).then((data) => {
      setPokemonData(data);
    });
  }, [props.id]);
};
one bit of code

Blockquote:

Technology is Neither Good, Nor Bad; Nor is it Neutral.

Melvin Kranzberg, Technology and History: “Kranzberg’s Laws”, 1986

Title with single image

Title with two images

Title with many images

Title with many images and list

  • List item one
  • List item two
  • List item three
  • List item four
  • List item five
  • Long long list item six
  • Not too many!

Title with many more images and list

  • List item one
  • List item two
  • List item three
  • List item four
  • List item five
  • Long long list item six
  • Not too many!

Questions?

state

event

Copy of Copy of Stately Slides

By Matt Pocock

Copy of Copy of Stately Slides

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