Casting Custom Fields

Casting custom fields are another common use case for custom fields. For example, we need to generate a slug field from the title field. We can use the cast method to cast the title field to a slug field, because we don't need to add slug field when creating a new post from outside the model.

src/models/post.ts

import { Model, Casts } from "@mongez/monpulse";
import { sluggable } from "./../utils/casts/sluggable";

export class Post extends Model {
  /**
   * Collection name
   */
  public static collection = "posts";

  /**
   * {@inheritDoc}
   */
  protected casts: Casts = {
    title: "string",
    content: "string",    
  };

  /**
   * {@inheritDoc}
   */
   protected customCasts: CustomCasts = {
    slug: sluggable("title"),
  };

The sluggable cast is a custom cast that we created to generate a slug from the title. We can use it as follows:

src/utils/casts/sluggable.ts

import { Model } from "@mongez/monpulse";
import slug from "@mongez/slug";

/**
 * Used for model castings
 */
export function sluggable(field: string) {
  return (model: Model) => {
    let value = model.get(field);

    if (!value) return "";

    return slug(String(value));
  };
}

Unlike casts, customCasts receives directly the model instance in the first argument this is we don't need to pass the field name to the cast function.