We need to deserialize in JS object to Model schema with help of class-transformer

Question

here the issue was when I was using plainToClass() my constructor will throw the error that the constructor parameter is not defined.

Here is my Mongo de query that returns the DeviceOperationsModel[] array. need to make the type check with class-transformer with the helper function of that library.

public async find(query: object): Promise<DeviceOperationsModel[]> {
        this.appLoggerService.info(`Finding records on the basis of the following query: ${JSON.stringify(query)}`,
            DeviceOperationsDbService.name);
        return await this.deviceOperationsModel.find(query).lean().exec();
    }

Here is the DeviceOperationsModel model class. is have nested class object

import { DeviceOperationsRequestModel } from './device-operations-request.model';
import { DeviceOperationsResponseModel } from './device-operations-response.model';

export class DeviceOperationsModel {
    readonly correlationId: string;
    readonly deviceId: string;
    readonly requestType: string;
    readonly request: DeviceOperationsRequestModel;
    readonly response: DeviceOperationsResponseModel;
    readonly createdAt: Date;
    readonly systemName: string;
    status: number;
    statusDescription: string;

    constructor(deviceOperationsData: any, correlationId: string, systemName: string, deviceOperationsResponseData?: any) {
        this.correlationId = correlationId;
        this.systemName = systemName;
        this.deviceId = deviceOperationsData.deviceId;
        this.requestType = deviceOperationsData.requestType;
        this.request = deviceOperationsData;
        this.response = deviceOperationsResponseData;
        this.createdAt = deviceOperationsData.createdAt;
        this.status = deviceOperationsData.status;
        this.statusDescription = deviceOperationsData.statusDescription;
    }
}

here is the deviceOperationsData class definition.

import { DeviceOperationsDestinationBlobModel } from './device-operations-destination-blob.model';

export class DeviceOperationsRequestModel {
    readonly serviceTimeoutInSeconds: number;
    readonly agentTimeoutInSeconds: number;
    readonly errorOnDisconnection: boolean;
    readonly destinationBlob: DeviceOperationsDestinationBlobModel;
    readonly metadata: object;
    readonly agentRetryCount: number;
    readonly agentRetryIntervalInSeconds: number;
    readonly progressUpdate: boolean;

    constructor(deviceOperation: any) {
        this.serviceTimeoutInSeconds = deviceOperation.serviceTimeoutInSeconds;
        this.agentTimeoutInSeconds = deviceOperation.agentTimeoutInSeconds;
        this.errorOnDisconnection = deviceOperation.errorOnDisconnection;
        this.destinationBlob = deviceOperation.destinationBlob;
        this.metadata = deviceOperation.metadata;
        this.agentRetryCount = deviceOperation.agentRetryCount;
        this.agentRetryIntervalInSeconds = deviceOperation.agentRetryIntervalInSeconds;
        this.progressUpdate = deviceOperation.progressUpdate;
    }
}

and so on.

what is the best way to typecast of the Mongo DB data here?

I have tried but with

try { 
const result = await this.deviceOperationsModel.find(query).lean().exec(); 
return plainToClass(DeviceOperationsModel, result as object[]); 
} catch (error) { 
console.log(error); 
} 

but got the correlation, devised, system name, etc are undefined.

Answer 1

In the example given in the class-transformer documentation, the class definition has no constructor. See here .

So, I suggest doing it with no constructor.

However, you seem to be expecting more data in the DeviceOperationsModel constructor than just the object. plainToClass() takes just an object and a class definition.

If you have optional properties that may not appear in the objects, mark them as optional in the class definition.

Also, you do not need to await in the find function. It returns a Promise, and you are not doing anything with the Promise result in the function. You don't even need to mark it async (but maybe you were inspecting it for debugging earlier...).