self-assert
[][repo]
Design objects that are fully responsible for their validity
[][npm]
[][license]
[][gh-workflow-ci]
🔗 [Documentation][docs] • [Live Demo][demo]
## Introduction
`self-assert` is a small TypeScript library that
helps you model domain rules _inside_ your objects
— not as external validators, but as collaborators in their own creation.
This library encourages a mindset where rules are expressed in
terms of the domain, and
**objects are created complete, valid, and meaningful from the start**.
## Installation
Install `self-assert` with `npm`:
```shell
npm install self-assert
```
## Quick Start
A common workflow is:
1. Define a single main factory method that validates parameters before
creating a new instance of the object.
2. Use `Assertion.requiring(...)` to define the rules.
3. Use `Ruleset.ensureAll(...)` to execute those rules inside the factory method.
4. Any additional static creation methods should delegate to the main one.
```ts
class Person {
static readonly nameNotBlank = Assertion.requiring(
"name.notBlank",
"Name must not be blank",
Requirements.isNotBlank
);
static named(name: string, ...) {
Ruleset.ensureAll(this.nameNotBlank.evaluateFor(name), ...otherRules);
return new this(name, ...);
}
protected constructor(protected name: string, ...) {}
}
```
If any assertion fails, a `RulesBroken` error is thrown.
This ensures your objects are **complete and valid** from the beginning.
Please refer to the [documentation][docs] or
[`examples/`](https://github.com/self-assert/self-assert/tree/main/examples)
for more details and use cases, such as:
- `assistants` to guide **form completion**
- validating **async rules**
- a built-in set of **reusable Requirements** for common checks
## Contributing
Contributions are welcome! See [Contributors' Guide][contributing] for details.
### Monorepo Structure
This package is part of the [`self-assert` monorepo][repo].
## License
[MIT][license]
[repo]: https://github.com/self-assert/self-assert
[license]: https://github.com/self-assert/self-assert/blob/main/LICENSE
[contributing]: https://github.com/self-assert/self-assert/blob/main/CONTRIBUTING.md
[docs]: https://self-assert.github.io
[demo]: https://codesandbox.io/p/sandbox/github/self-assert/self-assert-react-demo
[npm]: https://www.npmjs.com/package/self-assert
[gh-workflow-ci]: https://github.com/self-assert/self-assert/actions/workflows/ci.yml