打字稿中的错误函数定义

Question

我有一个 Angular 4 项目，我将文件上传到 Firebase 存储。我将上传程序代码基于 angular-firestarter。如果我运行此代码，它工作正常。

我已经在我的代码中包含了 upload.service.ts 并且它工作ed很好，但是在离开它一段时间后，upload.service.ts 将不再编译。我收到一个错误：'() 类型的参数 => void' 不可分配给“取消订阅”类型的参数。 类型 'void' 不能分配给类型 'undefined'。关于看起来像这样的函数：

pushUpload(upload: Upload, desktopKey: string) {
    const storageRef = firebase.storage().ref();
    const uploadTask = storageRef.child(`${this.basePath}/${upload.file.name}`).put(upload.file);

    uploadTask.on(firebase.storage.TaskEvent.STATE_CHANGED,
        (snapshot: any) => {
            // upload in progress
            upload.progress = (snapshot.bytesTransferred / snapshot.totalBytes) * 100;
        },
        (error) => {
            // upload failed
            console.log(error);
        },
        () => {
             // upload success
             upload.url = uploadTask.snapshot.downloadURL;
             upload.name = upload.file.name;
             this.saveDocumentData(upload, desktopKey);
        }
    );
}

在我的项目中似乎这个 on 函数的定义是错误的（如果我将它注释掉，应用程序可以正常工作）。关于什么可能导致此类问题以及如何解决它的任何想法？

如果我比较两个项目的 firebase.d.ts 文件，尽管两个项目在 package.json 中都有 "firebase": "^4.1.3"，但它们有点不同

来自 angular-firestarter

interface UploadTask {
    cancel ( ) : boolean ;
    catch (onRejected : (a : Error ) => any ) : firebase.Promise < any > ;
    on (event : firebase.storage.TaskEvent , nextOrObserver ? : null | Object , error ? : ( (a : Error ) => any ) | null , complete ? : ( ( ) => any ) | null ) : Function ;
    pause ( ) : boolean ;
    resume ( ) : boolean ;
    snapshot : firebase.storage.UploadTaskSnapshot ;
    then (onFulfilled ? : ( (a : firebase.storage.UploadTaskSnapshot ) => any ) | null , onRejected ? : ( (a : Error ) => any ) | null ) : firebase.Promise < any > ;
  }

来自我的项目：

  interface UploadTask {
    cancel ( ) : boolean ;
    catch (onRejected : (a : Error ) => any ) : firebase.Promise < any > ;
    on (event : firebase.storage.TaskEvent , nextOrObserver ? : firebase.Observer < any , any > | null | ( (a : Object ) => any ) , error ? : ( (a : Error ) => any ) | null , complete ? : ( firebase.Unsubscribe ) | null ) : Function ;
    pause ( ) : boolean ;
    resume ( ) : boolean ;
    snapshot : firebase.storage.UploadTaskSnapshot ;
    then (onFulfilled ? : ( (a : firebase.storage.UploadTaskSnapshot ) => any ) | null , onRejected ? : ( (a : Error ) => any ) | null ) : firebase.Promise < any > ;
  }

我已删除 node_modules 和 package-lock.json 并运行 npm install，但没有帮助。

我还尝试从包含 node_modules 的备份中恢复我的项目，然后它可以工作，但是当我删除 node_modules 和 package-lock.json 和 npm install 时，我得到了错误。

所以知道为什么我在我的项目中得到一个错误的类型定义文件，即使我安装了相同版本的 firebase？

我的 package.json 文件；

{
  "name": "docavea",
  "version": "0.0.0",
  "license": "MIT",
  "scripts": {
    "ng": "ng",
    "start": "ng serve --o",
    "build": "ng build",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e",
    "populate-db": "./node_modules/.bin/ts-node ./populate-db.ts",
    "populate-db2": "./node_modules/.bin/ts-node ./populate-db2.ts"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "^4.3.2",
    "@angular/common": "^4.3.2",
    "@angular/compiler": "^4.3.2",
    "@angular/core": "^4.3.2",
    "@angular/flex-layout": "^2.0.0-beta.8",
    "@angular/forms": "^4.3.2",
    "@angular/http": "^4.3.2",
    "@angular/platform-browser": "^4.3.2",
    "@angular/platform-browser-dynamic": "^4.3.2",
    "@angular/platform-server": "^4.3.2",
    "@angular/router": "^4.3.2",
    "angularfire2": "^4.0.0-rc.1",
    "core-js": "^2.4.1",
    "firebase": "^4.1.3",
    "global": "^4.3.2",
    "lodash": "^4.17.4",
    "ng2-pdf-viewer": "^1.1.0",
    "ngx-bootstrap": "^1.7.1",
    "rxjs": "^5.4.2",
    "zone.js": "^0.8.12"
  },
  "devDependencies": {
    "@angular/cli": "^1.2.6",
    "@angular/compiler-cli": "^4.3.2",
    "@types/jasmine": "2.5.38",
    "@types/node": "~6.0.60",
    "@types/lodash": "^4.14.67",
    "codelyzer": "~2.0.0",
    "jasmine-core": "~2.5.2",
    "jasmine-spec-reporter": "~3.2.0",
    "karma": "~1.4.1",
    "karma-chrome-launcher": "~2.0.0",
    "karma-cli": "~1.0.1",
    "karma-coverage-istanbul-reporter": "^0.2.0",
    "karma-jasmine": "~1.1.0",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "~5.1.0",
    "ts-node": "^3.1.0",
    "tslint": "~4.5.0",
    "typescript": "^2.4.2"
  }
}

Answer 1

问题来自于完成方法的处理程序：

() => {
         // upload success
         upload.url = uploadTask.snapshot.downloadURL;
         upload.name = upload.file.name;
         this.saveDocumentData(upload, desktopKey);
      }

这个函数的推断返回类型实际上是 void，它在旧版本的 firebase 上工作得很好，因为预期的类型是 ( ) => any 但在新版本已更改为 firebase.Unsubscribe，其定义为：

  type Unsubscribe = ( ) => undefined ;

因此 void 不能分配给 undefined 的错误。

您可以通过多种方式解决此问题，例如，您可以从箭头函数返回 undefined。