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