如何等待异步订阅完全填充全局变量？

Question

我有一个类似于以下内容的异步 firebase 调用：

this.fbProvider.fbGetProfile()
               .subscribe(p => {                                       
                            this.profile = p;
                         });

...但是我需要在其他功能中使用 this.profile...

console.log(this.profile.email);

...它会ps 返回一个错误：

Cannot read property 'email' of undefined

知道如何在需要使用之前等待订阅完全填充我的局部变量吗？

ps：我的问题比这更大，使用 .then() 等解决方案会使我的代码变得一团糟。我用 await 尝试了一些东西，但效果不佳。

`

Answer 1

您可以使用 async / await 承诺并在 api 调用完成后解决：

await new Promise(resolve => {
    this.fbProvider.fbGetProfile()
           .subscribe(p => {                                       
                        this.profile = p;
                        resolve();
                     });
});

记得在使用此代码的函数前加上 async。

Answer 2

  async uploadToStorage(element) {
    var imgUrl = "";
    var uploadTask = this.gallery_ref.child('Gallery/' + element.name).put(element);
    // Listen for state changes, errors, and completion of the upload.

    await new Promise(resolve => {

      uploadTask.on('state_changed', snapshot => {
        // Get task progress, including the number of bytes uploaded and the total number of bytes to be uploaded
        var progress = (uploadTask.snapshot.bytesTransferred / uploadTask.snapshot.totalBytes) * 100;
        console.log('Upload is ' + progress + '% done');
        }
      }, error => {

      }, function () {
        // Upload completed successfully, now we can get the download URL
        uploadTask.snapshot.ref.getDownloadURL().then(function (downloadURL) {
          imgUrl = downloadURL;
          console.log("url");
          console.log(imgUrl);
          resolve();
        });
      });
    })
    return imgUrl
  }

这是一个 firebase 函数，用于跟踪上传到 firebase 存储的文件的状态变化。使用上述答案中给出的 "await"，对我有用！

如何等待异步订阅完全填充全局变量？

How to wait for async subscribe to full fill a global variable?

asynchronous

firebase

angularfire

angular