How to declare a partial class in typescript

Question

For example, a DB Schema (Mongoose) like this:

@Schema()
class Schema {
  id: string;

  version: number;

  @Prop({
    type: String
  })
  name: string;

  somefiled: string;

  deleted: boolean;

  created_at: Date;

  updated_at: Date;
}

A Create Request Dto maybe like this:

class ReqDto {
  name: string;

  somefiled: string;
}
// other column fields may be generated
// so that we do not pass them from the request

A Get Request Response Dto maybe like this:

class ResDto {
  name: string;

  somefiled: string;

  // some transformed fields
  somefiled2: string;

  created_at: Date;

  updated_at: Date;
}
// some column fields may be hidden

I want to make ReqDto and ResDto a bit like this:

class ReqDto {
  // Pick fields from the schema Class (or Interface)
  [key: Pick];
}

class ResDto {
  // Pick fields from the schema Class (or Interface)
  [key: Pick];

  // some other fields
  somefiled2: string;
}

however, i have no idea how to realize it.

Here's my errored demo codes:

interface Schema {
  id: string;

  version: number;

  created_at: Date;

  updated_at: Date;
}

// OK
type Demo1 = {
  [P in keyof Schema]: Schema[P];
};

// error TS2464: A computed property name must be of type 'string', 'number', 'symbol', or 'any'.
// error TS7008: Member '[P in keyof' implicitly has an 'any' type.
// error TS2304: Cannot find name 'P'.
// error TS2304: Cannot find name 'keyof'.
// error TS2693: 'Schema' only refers to a type, but is being used as a value here.
// error TS1005: ']' expected.
// error TS1005: ';' expected.
// error TS1128: Declaration or statement expected.
interface Demo2 {
  [P in keyof Schema]: Schema[P];
};

// error TS2464: A computed property name must be of type 'string', 'number', 'symbol', or 'any'.
// error TS7008: Member '[P in keyof' implicitly has an 'any' type.
// error TS2304: Cannot find name 'P'.
// error TS2304: Cannot find name 'keyof'.
// error TS7008: Member 'Schema' implicitly has an 'any' type.
// error TS2300: Duplicate identifier 'Schema'.
// error TS7008: Member '[P]' implicitly has an 'any' type.
// error TS1005: ']' expected.
// error TS1005: ';' expected.
// error TS1068: Unexpected token. A constructor, method, accessor, or property was expected.
// error TS1005: ';' expected.
class Demo3 {
  [P in keyof Schema]: Schema[P];
};


// error TS1337: An index signature parameter type cannot be a union type. Consider using a mapped object type instead.
interface Demo4 {
  [P: keyof Schema]: Schema[P];
}

// error TS1337: An index signature parameter type cannot be a union type. Consider using a mapped object type instead.
class Demo5 {
  [P: keyof Schema]: Schema[P];
}

How to declare a partial class in typescript

0 Answers