class-validator-dto-example.ts

import { IsString, validateOrReject } from 'class-validator'

interface ICommandPackage {
    kind: 'commandPackage'
    command: string
}

interface IMessagePackage {
    kind: 'messagePackage'
    message: string
}

type IPackage = ICommandPackage | IMessagePackage

async function newPackageFromDTO(object: any): Promise<IPackage> {
    let res: IPackage
    switch (object.kind as IPackage["kind"]) {
        case 'commandPackage':
            res = new CommandPackage({ ...object })
            break;
        case 'messagePackage':
            res = new MessagePackage({ ...object })
            break
        default:
            throw new Error(`invalid kind: ${object.kind}`)
    }
    try {
        await validateOrReject(res)
        return res
    } catch (e) {
        throw e
    }
}

class CommandPackage implements ICommandPackage {
    kind: 'commandPackage' = 'commandPackage';

    @IsString()
    command: string;

    constructor({ command }: { command: string }) {
        this.command = command
    }
}

class MessagePackage implements IMessagePackage {
    kind: 'messagePackage' = 'messagePackage';

    @IsString()
    message: string;

    constructor({ message }: { message: string }) {
        this.message = message
    }
}

async function test() {
    let commandPackageDTO = {
        valid: {
            kind: 'commandPackage',
            command: 'go',
        },
        invalid: {
            kind: 'commandPackage',
            Command: 'go',
        }
    }
    let messagePackageDTO = {
        valid: {
            kind: 'messagePackage',
            message: 'yoyoyo',
        },
        invalid: {
            kind: 'messagePackage',
            messageee: 'yoyoyo',
        }
    }
    let invalidPackageDTO = {
        kind: 'lol',
        command: 'go',
    }

    async function test(name: string, dto: any) {
        try {
            let instance = await newPackageFromDTO(dto)
            console.log(name, instance)
        } catch (e) {
            console.error(name, 'invalid')
        }
    }

    test('commandPackageDTO.valid', commandPackageDTO.valid)
    test('commandPackageDTO.invalid', commandPackageDTO.invalid)
    test('messagePackageDTO.valid', messagePackageDTO.valid)
    test('messagePackageDTO.invalid', messagePackageDTO.invalid)
    test('invalidPackageDTO', invalidPackageDTO)
}
test()