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Handle Type parameter 'T' has a circular default. scenario better #52492
Description
Suggestion
I've done a lot of research about what I want, and nothing out there seems to reference it. So either what I want is very niche or not possible yet.
I have the following type defined:
type TableUpdateFn<T = any> = {
apiCall: (
query: Query,
progressCallback?: (progressType, loaded, total) => void,
isCancellable?: boolean
) => Promise<{ rows: T[]; count: number }>;
transformRows?: (
rows: T[],
customTableComponent: CustomTableComponent
) => Promise<void>;
selected?: (sourceObj: T) => boolean;
warning?: (sourceObj: T) => boolean;
};
The most important thing about this type is the type of the rows property (a single item, not the array type applied to it) returned by the apiCall promise. This type should determine how other functions are on the rest of the type.
Using generics seems like the most reasonable way to handle this, but unfortunately I'm stuck with either manually specifying the generic each time I use this type (which defeats the purpose of relying on apiCall for the type), or just defaulting to any.
What I would like to be able to do is something like this, which means the whole object matching this type will inherit the type of rows[0]:
type TableUpdateFn<
T = Awaited<ReturnType<this['apiCall']>>['rows'][0]
> = {
apiCall: (
query: Query,
progressCallback?: (progressType, loaded, total) => void,
isCancellable?: boolean
) => Promise<{ rows: T[]; count: number }>;
transformRows?: (
rows: T[],
customTableComponent: CustomTableComponent
) => Promise<void>;
selected?: (sourceObj: T) => boolean;
warning?: (sourceObj: T) => boolean;
};
🔍 Search Terms
interface self-reference recursion
Activity
jpike88 commentedon Jan 30, 2023
Another notes:
Even though typescript complains about the second example in my post above, my codebase lit up with some errors which actually helped me.
The below code snippet for example was invalid but got flagged, which again is a good thing:
Only problem is that the
selectedmethod in the above method errored because someVar became typeunknowninstead of the type I wanted (typeY)typescript-bot commentedon Feb 2, 2023
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