How to exclude a property type from an array of classes in Typescript

Question

Is it possible in typescript to deeply remove a prop from a class in an array nested in another class? this way for example:

class Nested {
  propX!: string;
  propY!: string;
  propZ!: string;
}

class Parent {
  propA!: string;
  propB!: number;
  propC!: string;
  nesteds!: Nested[]; 
}

// remove propZ from nesteds in Parrant class
class ParentInput implement Exclude<Parent, 'propC'|'nesteds.propZ'> {
  //...
}

Do you need it recursive or you know that nesteds occurs only at the top level? — Alberto Chiesa
– Alberto Chiesa, Commented Jun 16, 2021 at 15:27

Connor Low · Accepted Answer · 2021-06-16 15:46:51Z

1

You can use Pick and Exclude to filter out properties. Since Nested is, well, nested, you'll have to use extra type declarations to get it working:

// Grab every property except for 'propZ' out of Nested.
//   This is optional: you can just use `Pick<Nested...` directly below.
type FilteredNested = Pick<Nested, Exclude<keyof Nested, 'propZ'>>

// Grab every property except for 'propC' and 'nesteds' from Parent, 
//   then intersect a new `nesteds` definition using the above type
type FilteredParent = Pick<Parent, Exclude<keyof Parent, 'propC' | 'nesteds' >> & {
    nesteds: FilteredNested[]
}

class ParentInput implements FilteredParent {
    nesteds!: FilteredNested[];
    propA!: string;
    propB!: number;
}

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answered Jun 16, 2021 at 15:46

Connor Low

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