Make previous value available in @AfterUpdate function

By popular request, it would be very useful if we could also access the previous state of objects being updated in @AfterUpdate functions

For example:

@Entity()
export class CartItem {
    
    @AfterUpdate()
    notifyCustomer() {
        sendEmail(`An item in your cart has changed price from ??? to ${this.price}`
    }
}

Could become

@Entity()
export class CartItem {
    
    @AfterUpdate()
    notifyCustomer() {
        sendEmail(`An item in your cart has changed price from ${this.previous.price} to ${this.price}`
    }
}

TypeORM already knows the previous value, as it will only call @AfterUpdate if it detects a change, therefore, the feature would only require that to be exposed to developer.

Please see comment and thread - https://github.com/typeorm/typeorm/issues/1609#issuecomment-484303500

Thank you!

[Jantje2000]

Is there a workarround for this @pleerock ?

I needed this, so I made some code to use this. It’s written in a subscriber, in my case to add timeline and audit trail logging.

    beforeUpdate(event: UpdateEvent<any>): Promise<any> | void {
        event.updatedColumns.forEach((column) => {
            let key: string = column.databaseName;
            let oldValue = event.databaseEntity[column.propertyName];
            let newValue = event.entity[column.propertyName];

            console.log(`${key} was ${oldValue} en is nu ${newValue}`);
        });
    }

This code will loop through the updatedColumns which we know from the event, and will lookup them in the databaseEntity and the events entity.

Maybe it will help someone

[valjic1]

When using EventSubscriber you can hook to afterLoad event and set the retrieved entity as a class property.

@EventSubscriber()
export class CustomerSubscriber implements EntitySubscriberInterface<Customer> {
  customer: Customer;

  listenTo() {
    return Customer;
  }
  
  afterLoad(entity: Customer) {
    this.customer = entity;
  }

  afterUpdate(event: UpdateEvent<Customer>) {
    console.log(`Previous value: ${this.customer}`);
    console.log(`New value: ${event.entity}`);
  }
}