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May 3, 2024 23:54
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TypeORM entity relations type
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| // LIBRARY TYPES | |
| type _Arr<N, Result extends number[] = []> = Result['length'] extends N ? Result : _Arr<N, [...Result, 1]>; | |
| type _Decrement<N extends number> = _Arr<N> extends [any, ...infer U] ? U['length'] : 0; | |
| type _Concat<S1 extends string, S2 extends string> = [S1] extends [never] | |
| ? [S2] extends [never] | |
| ? '' | |
| : S2 | |
| : [S2] extends [never] | |
| ? S1 | |
| : `${S1}.${S2}` | |
| type _StringKeys<T> = Exclude<keyof T, symbol | number> | |
| type _ArrayElement<T> = T extends (infer E)[] ? E : T; | |
| type _RelationValue<TObject extends object, TDepth extends number, TPath extends string> = | |
| TDepth extends 0 | |
| ? TPath | |
| : TPath | _RelationPaths<_ArrayElement<TObject>, _Decrement<TDepth>, TPath> | |
| type _RelationMapping<T, TDepth extends number, TPrefix extends string> = { | |
| [P in _StringKeys<T>]: T[P] extends object | |
| ? _RelationValue<T[P], TDepth, _Concat<TPrefix, P>> | |
| : never; | |
| } | |
| type _RelationPaths<T, TDepth extends number, TPrefix extends string> = _RelationMapping<T, TDepth, TPrefix>[_StringKeys<T>] | |
| type Relations<T, TDepth extends number = 3> = _RelationPaths<T, TDepth, never>; | |
| // APPLICATION TYPES FOR TEST | |
| type Appartments = { | |
| room: number; | |
| persons: User[]; | |
| } | |
| type Address = { | |
| country: string; | |
| appartments: Appartments; | |
| } | |
| type User = { | |
| name: string; | |
| address: Address; | |
| } | |
| type UserRelations = Relations<User>; | |
| const relations: UserRelations[] = [ | |
| 'name', | |
| 'address', | |
| 'appartments', | |
| 'address.country', | |
| 'address.appartments', | |
| 'address.appartments.persons', | |
| 'address.appartments.persons.age', | |
| 'address.appartments.persons.address', | |
| ] |
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