根据其他属性动态限制 TypeScript 中对象属性的类型

Question

type MatchOperator = "==" | ">" | "<";

type Criteria<T, P extends keyof T> = {
    field: P,
    value: T[P],
    operator: MatchOperator,
}

interface User {
    name: string;
    age: number;
    id: number;
}

const adultCriteria: Criteria<User, "age"> = {
    field: "age",
    operator: ">",
    value: 18
}

是否有更好的方法来限制基于 field 的 value 的类型，如下所述？

const adultCriteria: Criteria<User> = {
    field: "age",
    operator: ">",
    value: 18
}

Answer 1

是的，有可能：

type Criteria<T> = {
    [P in keyof T]: {
        field: P,
        value: T[P],
        operator: MatchOperator
    }
}[keyof T]

这样你就得到了 3 种可能类型的联合类型组合：

type OnePossibleCriteria = Criteria<User>

type OnePossibleCriteria = {
    field: "name";
    value: string;
    operator: MatchOperator;
} | {
    field: "age";
    value: number;
    operator: MatchOperator;
} | {
    field: "id";
    value: number;
    operator: MatchOperator;
}

当您为它分配一个固定值时，它会缩小到其中之一。

const adultCriteria: OnePossibleCriteria = {
    field: "age",
    value: 18,
    operator: ">"
}

TypeScript Playground

根据其他属性动态限制 TypeScript 中对象属性的类型

Restricting types on object properties in TypeScript dynamically based on other properties

javascript

typescript

static-typing