DownloadURL在下面的代码中返回null

Question

当我更改文件时，它在firebase存储中成功更新，但是当我尝试获取downloadURL时，它显示为null。

fileChange(event: any) {
    const imageFolder: string = this.employee.id;
    const fileList: FileList = event.target.files;
    const file: File = fileList[0];
    const storageRef = firebase.storage().ref().child(`${imageFolder}/profile.jpg`).put(file);
    console.log(storageRef.snapshot.downloadURL);
}

Answer 1

put（）是异步的。如果你想在文件上传后获取网址，你必须这样做：

firebase.storage().ref().child(`${imageFolder}/profile.jpg`).put(file).then((snapshot) => {
     storageRef  = snapshot.downloadURL:
     console.log(snapshot.downloadURL);
});