42-Nodejs Course 2023: Saving Models

So, we did some good methods in our model to manipulate our model data, but we didn't save it yet. So, let's do it.

You didn't make any check for updates, right?

Yes, i'm reminding you, we should keep our packages up to date, so, let's do it.

yarn update

If there are any updates, then install it and let's proceed to the next step.

Saving the model

The save method will work as follows:

If the data contains an id field, then it will update the data, otherwise, it will create a new one.

Also, we need to check if the data has been modified or not, so if the data is not modified, then we will not save it.

// src/core/database/model/model.ts


export default abstract class Model extends CrudModel {
  // ...

  /**
   * Save the model data
   */
  public async save(mergedData: Document = {}) {
    // we can pass data to be updated
    this.merge(mergedData);

    // get primary column
    const primaryIdColumn = this.getStaticProperty("primaryIdColumn");

    // if the primary column exists in the data object
    // then perform update operation
    // otherwise, create a new record in database
    if (this.data[primaryIdColumn]) {
      // check if the document data is changed
      // if it is the same, then skip the update process
      if (areEqual(this.data, this.originalData)) return;

      // update the document
      await queryBuilder.update(
        this.getCollectionName(),
        {
          [primaryIdColumn]: this.data[primaryIdColumn],
        },
        this.data,
      );
    } else {
      // generate new id
      // the bind method is important here so the `this` can have a context to be taken from which is the Model.
      const generateNextId = this.getStaticProperty("generateNextId").bind(Model);
      this.data.id = await generateNextId();

      // update the current document data to have it with the `_id` column
      this.data = await queryBuilder.create(
        this.getCollectionName(),
        this.data,
      );
    }
  }
}

Let's split it into parts:

The method surely must be a async method.

The save method can accept a mergedData object, which will be merged with the current data object, this will allow us to pass the data to be updated in our model.

const user = new User;

await user.save({
  name: 'hasan'
});

Or we can just save the model without passing any data.

const user = new User({
  name: 'hasan'
});

await user.save();

Next we got the primary column using the getStaticProperty method, why? because the column is static, so we can get it from the class itself.

Next, we checked, does the data object contains that id, if so then the user is trying to update the data, otherwise, he is trying to create a new one.

If the user is trying to update the data, then we need to check if the data is changed or not, if it is not changed, then we will not update the data, because it is not necessary.

We're using areEqual function to check if the data is changed or not by comparing the original data with current data.

Next, we're using the update method from the queryBuilder to update the data, and we're passing the primary column value to the where clause.

If the user is trying to create a new one, then we need to generate a new id for the user, and then we need to create a new record in the database.

We're using the create method from the queryBuilder to create a new record in the database.

Now let's test it.

import User from './models/user';

const user = new User({
  name: 'hasan',
});

await user.save();

console.log(user.data); // { id: 1, name: 'hasan', _id: ObjectId('some_random_id') }