javascript - 如何在 TypeScript 中修复 "Initializer provides no value for this binding element and the binding element has no default value"？

Question

我正在将一个用 JavaScript 编写的 Apollo GraphQL API 项目迁移到 TypeScript。我在查找用户代码块时遇到错误，说:

var idArg: any Initializer provides no value for this binding element and the binding element has no default value.ts(2525)

  async findOne({ id: idArg } = {}) {
     // Red line here ^^^^^
    const user = await this.knex('users')
      .where('id', idArg)
      .first();

    if (!user) return;
    return user;
  }

目前我在不知道实际解决方案的情况下向其中添加了 any，警告消失了:

  async findOne({ id: idArg }: any = {}) {
    const user = await this.knex('users')
      .where('id', idArg)
      .first();

    if (!user) return;
    return user;
  }

但是我仍然想知道实际的解决方案。我应该添加 number 类型而不是 any 吗？但是当我这样做时，错误是:

Type '{}' is not assignable to type 'number'.ts(2322).

请帮忙。

Answer 1

根据您想要完成的任务，您可以通过多种方式解决此问题。

// The compiler checks the object { id: '1' } and it knows it has an id property
var { id } = { id: '1' }

/* The compiler is confused. It check the object {} and it knows it doesn't have 
a property id1, so it is telling you it doesn't know where to get the value 
for id1
*/
var { id1 } = {}

/* In this case the compiler knows the object doesn't have the property id2 but
since you provided a default value it uses it 'default value'.
 */
var { id2 = 'default value' } = {}

/* In your case there are a couple of solutions: */

// 1) Provide the value in the initializer
function findOne({ id: idArg } = { id: 'value here' }) {
    console.log(id)
}
findOne()

// 2) Provide a default value
function findOne1({ id: idArg = 'value here 1' } = {}) {}

// 3) Provide initializer and type definition
function findOne2({ id: idArg}: { id?: number } = {}) {}

// 3) Do not provide initializer
function findOne3({ id: idArg}: { id: number }) {}

Typescript playground link.