Within the .ts file, I have the following code snippet:
import { Observable } from 'rxjs/Rx';
export interface Loader<T> {
(q: string) : Observable<T[]>;
}
Further down in the same file, inside a different class, I have
if (this.field instanceof Loader)
This results in the following compile error:
Cannot find name 'Loader'.
I double-checked and confirmed that it is not a typo.
Any insights into why this error is occurring?
Attempting to use instanceof on interfaces is not a valid approach.
Interfaces do not translate to JS during compilation, so instanceof can only be determined at runtime.
In this scenario, employing a type guard is necessary, though the situation may be complex if Loader appears to be a function...
One potential solution is:
function isLoader(obj: any): obj is Loader {
return obj && typeof obj === "function";
}
The drawback here is that this type guard will categorize any function as a Loader, rather than solely a specific instance of Loader.
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