Assign Properties

Enhances models with data assignment capabilities for building modifiable model instances

The withAssignProperties mixin (also exported as withAssign) adds data assignment capabilities to your models. This allows you to create model instances with attached data and update them in a immutable way.

Usage

import { withAssignProperties } from '@doubletie/query-builder/mixins';
import { createDatabase, createModel } from '@doubletie/query-builder';
 
// Create a database and model
const db = createDatabase<Database>(/* config */);
const UserModel = createModel(db, 'users', 'id');
 
// Apply the assign mixin
const UserWithAssign = withAssignProperties(UserModel);
 
// Create a user
const user = await UserWithAssign.findById(1);
 
// Create a model instance with the user data
const userInstance = {
  ...UserWithAssign,
  ...user
};
 
// Use assign to create a new instance with updated data
const updatedUser = userInstance.assign({
  name: 'Updated Name',
  status: 'inactive'
});
 
// The original instance is unchanged
console.log(userInstance.name); // Original name
console.log(updatedUser.name);  // "Updated Name"
 
// Update in database
await UserModel.updateTable()
  .where('id', '=', updatedUser.id)
  .set({
    name: updatedUser.name,
    status: updatedUser.status
  })
  .execute();

API Reference

withAssignProperties()

function withAssignProperties<
  TDatabase,
  TTableName extends keyof TDatabase & string,
  TIdColumnName extends keyof TDatabase[TTableName] & string
>(model: ModelFunctions<TDatabase, TTableName, TIdColumnName>): ModelWithAssign<TDatabase, TTableName, TIdColumnName>

Enhances a model with the assign method.

ModelWithAssign

interface ModelWithAssign<TDatabase, TTableName, TIdColumnName> extends ModelFunctions<TDatabase, TTableName, TIdColumnName> {
  /**
   * Assigns data values to the model instance
   *
   * @param data - Data to assign (can be partial)
   * @returns Model instance with assigned data and all model properties
   */
  assign(data?: Partial<Selectable<TDatabase[TTableName]>>): any;
}

assign()

assign(data?: Partial<Selectable<TDatabase[TTableName]>>): any

Creates a new model instance with the assigned data. This method:

Creates a copy of the current instance
Merges the new data into the copy
Returns the new instance without modifying the original

Combining with Other Mixins

The assign mixin works well with other mixins to create rich model instances:

import { 
  withAssignProperties,
  withGlobalId
} from '@doubletie/query-builder/mixins';
 
// Apply multiple mixins
const UserWithFeatures = withAssignProperties(
  withGlobalId(UserModel, 'id', 'User')
);
 
// Create an instance
const userInstance = {
  ...UserWithFeatures, 
  ...user
};
 
// Use methods from both mixins
const globalId = userInstance.getGlobalId(userInstance.id);
const updatedUser = userInstance.assign({ name: 'New Name' });

Best Practices

Always create a new instance with assign rather than modifying the original
When updating the database, extract only the fields you want to update
Combine with other mixins like withGlobalId or withSlug for richer models
Consider using TypeScript to ensure type safety for model instances