打字稿：如何映射联合数组类型？ [英] Typescript: How to map over union array type?

问题描述

我有以下结构：

interface Test1 {
    number: number;
}
interface Test2 extends Test1 {
    text: string;
}

let test: Test1[] | Test2[] = [];
test.map(obj => {}); // does not work

我收到错误：

无法调用类型缺少调用签名的表达式。输入'{（this：[Test1，Test1，Test1，Test1，Test1]，callbackfn :( this：void，value：Test1，index：nu ...'没有兼容的呼叫签名

Cannot invoke an expression whose type lacks a call signature. Type '{ (this: [Test1, Test1, Test1, Test1, Test1], callbackfn: (this: void, value: Test1, index: nu...' has no compatible call signatures

我如何映射而不是测试变量？

How can I map over the test variable?

推荐答案

问题是对于联合类型，作为函数的成员也将被输入为联合类型，因此 map 的类型将是（< U>（callbackfn :(值：Test1，index：number，array：Test1 []）=> U，thisArg？：any）=> U []）|（< ; U>（callbackfn :(值：Test2，索引：数字，数组：Test2 []）=> U）就打字稿而言，哪个不可调用。

The problem is that for union types, members which are functions will also be typed as union types, so the type of map will be (<U>(callbackfn: (value: Test1, index: number, array: Test1[]) => U, thisArg?: any) => U[]) | (<U>(callbackfn: (value: Test2, index: number, array: Test2[]) => U) Which as far as typescript is concerned is not callable.

您可以声明 Test1 和 Test2

You can either declare an array of the union of Test1 and Test2

let test: (Test1 | Test2)[] = [];
test.map(obj => {}); 

或者你可以在拨打电话时使用类型断言：

Or you can use a type assertion when you make the call:

let test: Test1[] | Test2[] = [];
(test as Array<Test1|Test2>).map(o=> {});

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