Required and Pick

Learn Required for required and Pick for selecting.

Required and Pick

Required<T> turns T's optional properties into required ones; it drops the ?. Pick<T, K> keeps only the properties of T listed in K and discards the rest. Together they narrow and tighten an interface.

interface Uye {
  ad: string;
  eposta?: string;
}
type ZorunluUye = Required<Uye>;
type SadeceAd = Pick<Uye, "ad">;

Required vs Partial

Required is the opposite of Partial. Fields left optional in an interface may become required for some functions. For example, if eposta is required at registration you use Required<Uye>. This lets you reuse the same base type at different strictness levels.

Exercise Required member and summary

Define interface Uye with ad: string and eposta?: string. Write function kayit(u: Required<Uye>): void whose body prints the eposta via console.log(u.eposta). Call kayit({ ad: "Selin", eposta: "s@x.com" }).

Show example solution

interface Uye {
  ad: string;
  eposta?: string;
}
function kayit(u: Required<Uye>): void {
  console.log(u.eposta);
}
kayit({ ad: "Selin", eposta: "s@x.com" });

Test yourself

What does <code>Pick<Uye, "ad" | "eposta"></code> produce?
```
interface Uye { ad: string; eposta?: string; }
type T = Pick<Uye, "ad" | "eposta">;
```
- A type with all properties optional
- A type with ad and eposta removed
- A type with all properties required
- A type with only ad and eposta properties
Show answer

A type with only ad and eposta properties — Pick keeps the named properties and discards the rest. Optional is Partial, removal is Omit, required is Required.

Select properties with Pick

interface Urun { ad: string; fiyat: number; stok: number; }
type Ozet = ____<Urun, "ad" | "fiyat">;

Show answer

interface Urun { ad: string; fiyat: number; stok: number; }
type Ozet = Pick<Urun, "ad" | "fiyat">;

Required and Pick parts

Required<T>

Makes optionals required
Pick<T, K>

Selects properties in K
Pick<Uye, "ad">

Single property selection
Required<Uye>

eposta becomes required

Next lesson: Omit and Record

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