16 replies

How to type a generic selection function

I've been trying to implement a generic select function but can't figure out how to type it
Something like this:

async function select<T extends Something>(selectFields: T, limit: number): SomethingReturn> {
  const db = await getClient()
  const res = await db.select(selectFields).from(users).limit(limit)
  return res
}

const users = await select({ name: users.name }, 10)
// Should be typed `{ name: string }[]`

async function select<T extends Something>(selectFields: T, limit: number): SomethingReturn> {
  const db = await getClient()
  const res = await db.select(selectFields).from(users).limit(limit)
  return res
}

const users = await select({ name: users.name }, 10)
// Should be typed `{ name: string }[]`

What type should I use to replace

Something

Something

and

SomethingReturn

SomethingReturn

I tried a combination of

type TSchema = ExtractTablesWithRelations<typeof schema>
type TFields = TSchema['users']['columns']

type TSchema = ExtractTablesWithRelations<typeof schema>
type TFields = TSchema['users']['columns']

and multiple combinations of

PgSelect

PgSelect

PgSelectBase

PgSelectBase

but can't get it to work properly
Any help appreciated

Drizzle Team•2y ago•

16 replies

alexb

How to type a generic selection function

I've been trying to implement a generic select function but can't figure out how to type it
Something like this:

async function select<T extends Something>(selectFields: T, limit: number): SomethingReturn> {
  const db = await getClient()
  const res = await db.select(selectFields).from(users).limit(limit)
  return res
}

const users = await select({ name: users.name }, 10)
// Should be typed `{ name: string }[]`

async function select<T extends Something>(selectFields: T, limit: number): SomethingReturn> {
  const db = await getClient()
  const res = await db.select(selectFields).from(users).limit(limit)
  return res
}

const users = await select({ name: users.name }, 10)
// Should be typed `{ name: string }[]`

What type should I use to replace

Something

Something

and

SomethingReturn

SomethingReturn

I tried a combination of

type TSchema = ExtractTablesWithRelations<typeof schema>
type TFields = TSchema['users']['columns']

type TSchema = ExtractTablesWithRelations<typeof schema>
type TFields = TSchema['users']['columns']

and multiple combinations of

PgSelect

PgSelect

PgSelectBase

PgSelectBase

but can't get it to work properly
Any help appreciated

How to type a generic selection function

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