Standard libraries that lift up your code.
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import {Model} from '../Model'
import {ModelBuilder} from '../ModelBuilder'
import {AbstractBuilder} from '../../builder/AbstractBuilder'
import {ResultCollection} from '../../builder/result/ResultCollection'
import {Collection, ErrorWithContext, Maybe} from '../../../util'
import {QuerySource} from '../../types'
import {RelationBuilder} from './RelationBuilder'
import {InjectionAware} from '../../../di'
/** Type alias for possible values of a relation. */
export type RelationValue<T2> = Maybe<Collection<T2> | T2>
/** Error thrown when a relation result is accessed synchronously before it is loaded. */
export class RelationNotLoadedError extends ErrorWithContext {
context: {[key: string]: any} = {},
) {
super('Attempted to get value of relation that has not yet been loaded.', context)
* Base class for inter-model relation implementations.
export abstract class Relation<T extends Model<T>, T2 extends Model<T2>, V extends RelationValue<T2>> extends InjectionAware {
protected constructor(
/** The model related from. */
protected parent: T,
/** The model related to. */
public readonly related: T2,
) {
/** Get the value of the key field from the parent model. */
protected abstract get parentValue(): any
/** Create a new relation builder query for this relation instance. */
public abstract query(): RelationBuilder<T2>
/** Limit the results of the builder to only this relation's rows. */
public abstract applyScope(where: AbstractBuilder<T2>): void
/** Create a relation query that will eager-load the result of this relation for a set of models. */
public abstract buildEagerQuery(parentQuery: ModelBuilder<T>, result: Collection<T>): ModelBuilder<T2>
/** Given a set of possibly-related instances, filter out the ones that are relevant to the parent. */
public abstract matchResults(possiblyRelated: Collection<T>): Collection<T>
/** Set the value of the relation. */
public abstract setValue(related: V): void
/** Get the value of the relation. */
public abstract getValue(): V
/** Returns true if the relation has been loaded. */
public abstract isLoaded(): boolean
/** Get a collection of the results of this relation. */
public fetch(): ResultCollection<T2> {
return this.query().get()
/** Resolve the result of this relation. */
public abstract get(): Promise<V>
* Makes the relation "thenable" so relation methods on models can be awaited
* to yield the result of the relation.
* @example
* ```ts
* const rows = await myModelInstance.myHasManyRelation() -- rows is a Collection
* ```
* @param resolve
* @param reject
public then(resolve: (result: V) => unknown, reject: (e: Error) => unknown): void {
if ( this.isLoaded() ) {
} else {
.then(result => {
if ( result instanceof Collection ) {
/** Get the value of this relation. */
public get value(): V {
return this.getValue()
/** Get the query source for the related model in this relation. */
public get relatedQuerySource(): QuerySource {
const related = this.related.constructor as typeof Model
return related.querySource()
/** Get a new builder instance for this relation. */
public builder(): RelationBuilder<T2> {
return this.make(RelationBuilder, this)