Working with TypeScript Types

1. Using Generated Model Types

import type { User, Post } from "@prisma/client";
function greet(u: User) { return `Hi, ${u.name ?? "friend"}`; }

Type	Detail
User	All scalar fields of the model
Relations	Not included by default

import type { Prisma } from "@prisma/client";
type UserWithPosts = Prisma.UserGetPayload<{ include: { posts: true } }>;

Helper	Use
`Prisma.<Model>GetPayload<T>`	Compute query result type
Validator	`Prisma.validator<Prisma.UserDefaultArgs>()(args)`

function isAdmin(u: User): u is User & { role: "ADMIN" } {
  return u.role === "ADMIN";
}

Pattern	Use
Predicate	Narrow union types
Discriminator	Combine with literal types

type Identifier = { id: number } | { email: string };

Use	Detail
Polymorphic IDs	findBy either id or email
Result variants	{ kind: "ok" } \| { kind: "err" }

API	Detail
`$queryRaw<T>`	Generic return type
`Prisma.sql`	Safe composition

async function findById<K extends keyof typeof prisma>(
  model: K, id: number
) {
  return (prisma[model] as any).findUnique({ where: { id } });
}

Trade-off	Detail
Reusability	One helper for all models
Type safety	Loses inference; consider per-model

{ "compilerOptions": { "strict": true, "strictNullChecks": true } }

Setting	Effect
strict	Enables all strict checks
strictNullChecks	Treat `null/undefined` distinctly