I'm just starting with TypeScript and I ran across a situation in which the type definitions for a library I'm using is wrong. In my case, the library is Massive,js, and here are the type definitions.
The problem is that some functions should return either Promise<T[]>
or Promise<T>
, but the typings say it's always Promise<T[]>
.
interface Table<T> {
// other functions omitted for simplicity
save(data: object): Promise<T[]>;
insert(data: object): Promise<T[]>;
update(dataOrCriteria: object, changesMap?: object): Promise<T[]>;
}
How do I fix the above functions so they would return either Promise<T[]>
or Promise<T>
?
You can define multiple types.
interface Table<T> {
// other functions omitted for simplicity
save(data: object): Promise<T | T[]>;
insert(data: object): Promise<T | T[]>;
update(dataOrCriteria: object, changesMap?: object): Promise<T | T[]>;
}
Or when using the library just make T an array of items.