TypeScript中的互斥类型实现方法示例

type obj = {
  a?:string;
  b?:string;
  c?:string;
  d?:string;
  e?:string;
}

type obj = { [P in "a" | "b" | "c" | "d" | "e"]?: string };

let amazing: never;
amazing = 12;// 报错：amazing是never类型不能分配给number类型
amazing = true;// 报错：amazing是never类型不能分配给boolean类型
amazing = "真神奇";// 报错：amazing是never类型不能分配给string类型
amazing = {};// 报错：amazing是never类型不能分配给{}类型
amazing = [];// 报错：amazing是never类型不能分配给[]类型

type P = Exclude<"a" | "b" | "c" | "d", "b" | "c"> // "a" | "d"

type A =  { [P in "name" | "title"]?: string };

type UnionType = keyof A; // "name" | "title"

// 定义排除类型：将U从T中剔除, keyof 会取出T与U的所有键, 限定P的取值范围为T中的所有键, 并将其类型设为never
type Without<T, U> = { [P in Exclude<keyof T, keyof U>]?: never };

// 定义互斥类型，T或U只有一个能出现（互相剔除时，被剔除方必须存在）
type XOR<T, U> = (Without<T, U> & U) | (Without<U, T> & T);

// A类型
type A = {
  name: string;
};

// B类型
type B = {
  title: string;
};

// A和B两种类型只有一个能出现
type AOrB = XOR<A, B>;

// 传值测试
const AOrB1: AOrB = { name: "姓名" }; // 编译通过
const AOrB2: AOrB = { title: "标题" }; // 编译通过
const AOrB3: AOrB = { title: "标题", name: "姓名" }; // 报错: Type '{ title: string; name: string; }' is not assignable to type 'AOrB'.
const AOrB4: AOrB = { name: "姓名", otherKey: "" }; // 报错：Type '{ name: string; otherKey: string; }' is not assignable to type 'AOrB'.

type AOB = ({ name?: never } & {
      title: string;
    }) | ({ title?: never } & {
      name: string;
    });

// 传值测试
const a: AOB = { name: "姓名" }; // 编译通过
const b: AOB = { title: "标题" }; // 编译通过
const c: AOB = { title: "标题", name: "姓名" }; // 报错
const d: AOB = { title: "标题", otherKey: "" }; // 报错