在测试我的UserRouter时,我使用了一个json文件
data.json
[
{
"id": 1,
"name": "Luke Cage",
"aliases": ["Carl Lucas", "Power Man", "Mr. Bulletproof", "Hero for Hire"],
"occupation": "bartender",
"gender": "male",
"height": {
"ft": 6,
"in": 3
},
"hair": "bald",
"eyes": "brown",
"powers": [
"strength",
"durability",
"healing"
]
},
{
...
}
]
构建我的应用程序,我得到以下TS错误
ERROR in ...../UserRouter.ts
(30,27): error TS7006: Parameter 'user' implicitly has an 'any' type.
UserRouter.ts
import {Router, Request, Response, NextFunction} from 'express';
const Users = require('../data');
export class UserRouter {
router: Router;
constructor() {
...
}
/**
* GET one User by id
*/
public getOne(req: Request, res: Response, _next: NextFunction) {
let query = parseInt(req.params.id);
/*[30]->*/let user = Users.find(user => user.id === query);
if (user) {
res.status(200)
.send({
message: 'Success',
status: res.status,
user
});
}
else {
res.status(404)
.send({
message: 'No User found with the given id.',
status: res.status
});
}
}
}
const userRouter = new UserRouter().router;
export default userRouter;
最小误差再现
export const users = require('../data'); // presumes @types/node are installed
const foundUser = users.find(user => user.id === 42);
// error: Parameter 'user' implicitly has an 'any' type.ts(7006)
推荐解决方案:——resolveJsonModule
The simplest way for your case is to use
--解析Json模块
compiler option:
import users from "./data.json" // `import` instead of `require`
const foundUser = users.find(user => user.id === 42); // user is strongly typed, no `any`!
除了静态JSON导入,还有其他一些替代方案。
选项1:显式用户类型(简单,不检查)
type User = { id: number; name: string /* and others */ }
const foundUser = users.find((user: User) => user.id === 42)
方案2:类型防护(中间)
类型警卫
are a good middleground between simplicity and strong types:
function isUserArray(maybeUserArr: any): maybeUserArr is Array<User> {
return Array.isArray(maybeUserArr) && maybeUserArr.every(isUser)
}
function isUser(user: any): user is User {
return "id" in user && "name" in user
}
if (isUserArray(users)) {
const foundUser = users.find((user) => user.id === 42)
}
You can even switch to
断言函数
(TS 3.7+) to get rid of
if
and throw an error instead.
function assertIsUserArray(maybeUserArr: any): asserts maybeUserArr is Array<User> {
if(!isUserArray(maybeUserArr)) throw Error("wrong json type")
}
assertIsUserArray(users)
const foundUser = users.find((user) => user.id === 42) // works
选项3:运行时类型的系统库(复杂)
对于更复杂的情况,可以集成像io-ts或ts-runtime这样的运行时类型检查库。
不推荐的解决方案
noImplicitAny:错
undermines many useful checks of the type system:
function add(s1, s2) { // s1,s2 implicitely get `any` type
return s1 * s2 // `any` type allows string multiplication and all sorts of types :(
}
add("foo", 42)
最好为User提供显式的User类型。这将避免将任何类型传播到内层。相反,输入和验证保留在外层API层的JSON处理代码中。