TypeScript:迭代接口(interface)字段不起作用

Question

我正在尝试遍历具有接口(interface)的对象的键，但 TypeScript 无法识别键的类型。

interface Resources {
  food?: number
  water?: number
  wood?: number
  coal?: number
  stone?: number
  metal?: number
  oil?: number
  power?: number
}

class Game {
  resources: Resources = {}

  addResources = (newResources: Resources) => {
    Object.keys(newResources).forEach(key => {
      // Error:(17, 11) TS7053: Element implicitly has an 'any' type because expression of type 'string' can't be used to index type 'Resources'.
     //  No index signature with a parameter of type 'string' was found on type 'Resources'.
      if (this.resources[key]) {
        this.resources[key] += newResources[key]
      } else {
        this.resources[key] = newResources[key]
      }
    })
  }
}

我应该如何输入它以便 Typescript 能够理解迭代？

Answer 1

是的，Object.keys()返回 string[]这是故意的https://github.com/Microsoft/TypeScript/issues/12870

(Object.keys(newResources) as Array<keyof Resources>).forEach(...)为了救援。

更新

(Object.keys(newResources) as Array<keyof typeof newResources>).forEach(...)也有帮助。