Question

我要将文件放入Firebase存储中，我浏览了一张图像列表，并希望将它们一张一张地放在Firebase中。但是Map并不希望完成图像的上传，它会同时启动所有图像，我希望它一张一张。

createProject() {
    let url;
    let prevState = this.state;
    let project = {
        projectName: prevState.projectName,
        description: prevState.description,
        images: [],
    }
    let getUrl = function (url) {
        console.log('DONE' + url);
    }
    prevState.project.images.map(async (image, key) => {
        let url = await this.putFile(image);
        getUrl(url);
    })
}

putFile(file, getUrl) {
    return new Promise(function (resolve, reject) {
        let storageRef = fire.storage().ref('Projects/Images/');
        const image = file;
        const name = file.imageName;
        const metadata = {
            contentType: file.data.type,
        };
        const task = storageRef.child(name).put(image.data, metadata);

        task.on('state_changed', function (snapshot) {
            var progress = (snapshot.bytesTransferred / snapshot.totalBytes) * 100;
            console.log('Upload is ' + progress + '% done');
            switch (snapshot.state) {
                case firebase.storage.TaskState.PAUSED: // or 'paused'
                    console.log('Upload is paused');
                    break;
                case firebase.storage.TaskState.RUNNING: // or 'running'
                    console.log('Upload is running');
                    break;
            }
        }, function (error) {

        }, function () {
            task.snapshot.ref.getDownloadURL().then(function (downloadURL) {
                resolve(downloadURL);
            });
        });

    });
}

我希望Map等待上一个“解决”。

Answer 1

您可以改用异步for-of循环：

async createProject() {
  // ...
  for (let image of prevState.project.images) {
    let url = await this.putFile(image);
    getUrl(url);
  }
}

反应-异步的异步等待问题

1 个答案: