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https://github.com/sandromaglione/effect-getting-started
Example apps to get started using all the features of effect: Context, Layer, Runtime, Scope and more 🪄
https://github.com/sandromaglione/effect-getting-started
effect effect-ts functional-programming
Last synced: about 11 hours ago
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Example apps to get started using all the features of effect: Context, Layer, Runtime, Scope and more 🪄
- Host: GitHub
- URL: https://github.com/sandromaglione/effect-getting-started
- Owner: SandroMaglione
- Created: 2023-11-10T05:28:58.000Z (about 1 year ago)
- Default Branch: main
- Last Pushed: 2024-06-11T17:00:42.000Z (5 months ago)
- Last Synced: 2024-06-12T01:23:53.810Z (5 months ago)
- Topics: effect, effect-ts, functional-programming
- Language: TypeScript
- Homepage: https://www.sandromaglione.com/newsletter
- Size: 157 KB
- Stars: 26
- Watchers: 4
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# How to `effect`
***
This project is part of my weekly newsletter at [**sandromaglione.com**](https://www.sandromaglione.com/newsletter?ref=Github&utm_medium=newsletter_project&utm_term=xstate&utm_term=effect).
## Project structure
This is a collection of examples of how to use [`effect`](https://github.com/Effect-TS/effect).
This is a **deep** dive exploration of the features and *internals* offered by `effect`.
## How to use
Install:
```bash
pnpm install
```
Then you can run each script (take a look at `package.json` for the list of all the scripts you can run):
```bash
pnpm run index
```
> **Note**: The convention is that files that start with a lowercase letter are runnable scripts
Take a look also at [`test`](/test/).
***
## Notes
### Base64
No need to install extra libraries like `js-base64`. The `Encoding` module provides encoding/decoding of base64.
### `Context` (`Tag`)
Inside [`GlobalValue`](https://github.com/Effect-TS/effect/blob/main/packages/effect/src/GlobalValue.ts#L17) Effect stores a `globalStore` of type `Map`.
Inside this store the `Context` module registers a [`tagRegistry`](https://github.com/Effect-TS/effect/blob/14e4393ebe3ba2635c73297bf7cd6750c883e669/packages/effect/src/internal/context.ts#L59):
```ts
const tagRegistry = globalValue("effect/Context/Tag/tagRegistry", () => new Map>())
```
Inside this registry Effect collects all `Tag`s, created using `Context.Tag` by calling the *internal* [`makeTag`](https://github.com/Effect-TS/effect/blob/14e4393ebe3ba2635c73297bf7cd6750c883e669/packages/effect/src/internal/context.ts#L62).
> [!Note]
> When you pass an `identifier` to `Context.Tag` you specify a key for the `tagRegistry`. Effect [checks the registry](https://github.com/Effect-TS/effect/blob/14e4393ebe3ba2635c73297bf7cd6750c883e669/packages/effect/src/internal/context.ts#L63-L65) when accessing and creating a new tag.
A `Tag` is an instance of [`Pipeable`](https://github.com/Effect-TS/effect/blob/main/packages/effect/src/Pipeable.ts#L9). This allows to chain `.pipe` to an instance of `Tag` to extract the methods of a service:
```ts
interface Base64Service {
readonly decode: (
source: string
) => Effect.Effect;
}
export const Base64Service = Context.Tag("@app/Base64Service");
/** Use `pipe` to extract the methods from the service 👆 */
const result = Base64.Base64Service.pipe(
Effect.flatMap((base64) => base64.decode("Zm9vYmFy")),
Effect.provide(Base64.Base64ServiceLive), // 👈 Then provide a valid instance
Effect.runSync
);
```
`Tag` (`Context`) is also a valid [instance of `Effect`](https://github.com/Effect-TS/effect/blob/14e4393ebe3ba2635c73297bf7cd6750c883e669/packages/effect/src/Effect.ts#L150-L157). This allows to use methods such as `flatMap`.
### `ContextProto`
An instance of `Context` is created by copying a [context prototype](https://github.com/Effect-TS/effect/blob/14e4393ebe3ba2635c73297bf7cd6750c883e669/packages/effect/src/internal/context.ts#L87-L122) (using [`Object.create`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create) inside the *internal* [`makeContext`](https://github.com/Effect-TS/effect/blob/14e4393ebe3ba2635c73297bf7cd6750c883e669/packages/effect/src/internal/context.ts#L125-L129))
### `Iterable`
The [Iteration protocols](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols) define an `Iterable` interface:
```ts
interface Iterator {
next(...args: [] | [TNext]): IteratorResult;
return?(value?: TReturn): IteratorResult;
throw?(e?: any): IteratorResult;
}
interface Iterable {
[Symbol.iterator](): Iterator;
}
```
The `Effect` type [defines an iterator](https://github.com/Effect-TS/effect/blob/14e4393ebe3ba2635c73297bf7cd6750c883e669/packages/effect/src/Effect.ts#L1123). This allows to use `yield*` in `Effect.gen` ([`EffectGen`](https://github.com/Effect-TS/effect/blob/14e4393ebe3ba2635c73297bf7cd6750c883e669/packages/effect/src/internal/core-effect.ts#L778-L784) and [`SingleShotGen`](https://github.com/Effect-TS/effect/blob/14e4393ebe3ba2635c73297bf7cd6750c883e669/packages/effect/src/Utils.ts#L102-L146)).
This is also used by Effect to define methods such as [`map`](https://github.com/Effect-TS/effect/blob/14e4393ebe3ba2635c73297bf7cd6750c883e669/packages/effect/src/internal/Iterable.ts#L43-L54).