@nhpd/from-json v1.1.0

from-json

Easily convert your raw json coming to the initialized classes with typescript annotations

See usage and specs on github: https://github.com/NeverHappened/from-json

Notes

Before usage you must import 'reflect-metadata' package into your project. It's global, so you can add it in a separate script. For example, in polyfills.ts for Angular 2+.

import 'reflect-metadata';

Also you need to set "emitDecoratorMetadata": true in your tsconfig.json to autodiscover feature and array detection to work

Usage

You can actually look at the specs to see the working examples (src/specs/*)

Simple case - convert simple types

1. Annotate your class propertis that you want to convert with @Property annotations convertable-class.ts

import { Property } from '@nhpd/from-json';

class ConvertableClass {
  @Property()
  public convertableProperty: string;
}

2. Than use the fromJson method to intantiate your class automatically test.ts

import { fromJson, typeInfo } from '@nhpd/from-json';
import { ConvertableClass } from './convertable-class';

const raw = { convertableProperty: 'Test' };
const convertedClass = fromJson<ConvertableClass>(typeInfo(ConvertableClass), raw); // instance of ConvertableClass
console.log(convertedClass.convertableProperty === 'Test'); // true

For properties that are itself classes annotated

convertable-class.ts

import { Property } from '@nhpd/from-json';

class DifferentClass {
  @Property()
  public prop: string;
}
class ConvertableClass {
  @Property({ autodiscover: true })
  public convertableProperty: DifferentClass;
}

Simple arrays conversion:

Just specify @Property()

Custom class arrays conversion: typescript @Property({ customClass: DifferentClass })

convertable-class.ts

import { Property } from '@nhpd/from-json';

class DifferentClass {
  @Property({})
  public prop: string;
}
class ConvertableClass {
  @Property({ autodiscover: true })
  public convertableProperty: DifferentClass[];
}

Generic classes

They present a problem, cause we cannot infer the types of generic classes in annotations. The workaround for that is to pass around additional (recursive) type info to fromJson method: convertable-class.ts

import { Property } from '@nhpd/from-json';

class ConcretePropertyClass {
  @Property()
  public prop: string;
}

class GenericClass<T> {
  @Property({ generic: true })
  public convertableProperty: T;
}

test.ts

const raw = { convertableProperty: { prop: 'Test' } };
const info = typeInfo(GenericClass, { convertableProperty: typeInfo(ConcretePropertyClass) });
const converted = fromJson<GenericClass<ConcretePropertyClass>>(raw, info);
console.log(converted.convertableProperty.prop) === 'Test'; // true

For autoconversion of classes that cannot be annotated with @Property (For example, Date), use

class SimpleClass {
  @Property({ createFunction: (isoString) => new Date(isoString) })
  public convertableProperty: Date;
}

Gotchas

1. You cannot use autodiscover if you have an array, because we cannot infer the generic constructor from the Array class. Use customClass.
2. You should use autodiscover to automatically convert classes with @Property inside
3. If you don't want to convert into the class (It's simple numbers/strings/interface), just don't use anything at all
4. We don't need a customClass if using { generic: true }, because it'll be taken from the TypeInfo passed in fromJson function

Development

Install dependencies

yarn

Run tests

yarn test

Release

Increase version in package.json

Compile typescript

yarn run compile

Publish to npm

npm publish

Run tests

npm run test