GitHub user DadiBit created a discussion: Better type safety schemas
Greetings, I just started exploring Arrow and DuckDB, and I must admit it's
quite interesting, however... I was hurting a bit to not be able to get full
type safety with typescript intellisense of vscodium. I saw #192, and it looks
somewhat related.
When I request the fields I just end up with an array of fields... Meh, having
a typed object would be much cooler, wouldn't it?
Here's how I partially implemented my type safety:
##### `helper.ts` allows me to infer the constructor params as tuples:
```typescript
import { Schema, Field } from "@apache-arrow/ts";
// See: https://stackoverflow.com/a/55344772
type Tail<T extends any[]> = T extends [infer A, ...infer R] ? R : never;
export type Fields = { [name: string]: Tail<ConstructorParameters<typeof
Field>> };
type FieldsTypeMap<T extends Fields> = { [K in keyof T]: T[K][0] };
// Factory to generate typed schema
export function schemaFactory<T extends Fields>(fields: T) {
const _fields = Object.entries(fields).map(([name, field]) => new Field(name,
...field));
return new Schema<FieldsTypeMap<T>>(_fields);
}
```
##### `student.ts` to check out intellisense
```typescript
import { Uint8, Utf8 } from "@apache-arrow/ts";
import { Fields, schemaFactory } from "./helper";
export const fields = {
// here it fails to help me with names, but types are checked, that's
something!
'name': [new Utf8(), true],
'age': [new Uint8(), true],
} satisfies Fields; // satisfies is very import, it doesn't erase the keys!
// Now, `schema`, techincally has the generic specific for my type
// When using `.fields` you get something out of it:
// But it's just Field<Utf8 | Uint8>[]... What the hell, I lose some
information, namely the key!
export const schema = schemaFactory(fields);
```
So I would like to ask if there's any chance to modify the library to return
more meaningful types. This **would break some code**, since the types returned
would change and some dev might depend on the type defintions (altough not
super useful).
GitHub link: https://github.com/apache/arrow-js/discussions/232
----
This is an automatically sent email for [email protected].
To unsubscribe, please send an email to: [email protected]
