TypeScript開關盒徹底檢查不起作用？

Question

const changeToInvalidations = (change: Change): Array<Invalidation> => { 
    switch (change.resourceType) { 
    case "brand": 
     switch (change.type) { 
     case "added": 
      return [{ type: "page", value: "productListing" }] 
     case "updated": 
      return [{ type: "brand", value: change.resourceId }] 
     case "removed": 
      return [{ type: "brand", value: change.resourceId }] 
     } 
    case "product": 
     switch (change.type) { 
     case "added": 
      return [{ type: "page", value: "productListing" }] 
     case "updated": 
      return [{ type: "product", value: change.resourceId }] 
     case "removed": 
      return [ 
      { type: "page", value: "productListing" }, // pagination reflow 
      { type: "brand", value: change.resourceId }, 
      ] 
     } 
    } 
} 

Change類型的定義：

type Change = { 
    type: "added" | "updated" | "removed" 
    resourceId: number 
    resourceType: "brand" | "product" 
} 

錯誤：

Function lacks ending return statement and return type does not include 'undefined'

但是從閱讀本https://www.typescriptlang.org/docs/handbook/advanced-types.html

看來我應該是好去。我做錯了什麼？

Answer 1

錯誤消息可能指的是缺少default:的情況，其中沒有定義返回語句。如果resourceType或type屬性是undefined它將切換到default的情況。