我正在将文件上传到Google Cloud。完成后,我想返回文件URL和一些元数据。我想这样做:
blobStream.on('finish', () => {
var fileSize;
var fileCreated;
fileUpload.getMetadata()
.then(metadata => {
const mObj = metadata[0];
fileSize = mObj.size;
fileCreated = mObj.timeCreated;
});
fileUpload.getSignedUrl({
action: 'read',
expires: '03-09-2491'
}).then(signedUrl => {
let response = {};
response.name = newFileName;
response.size = fileSize;
response.created = fileCreated;
response.url = signedUrl[0];
resolve(response);
}).catch(error => {
reject(error);
});
});
问题是,getSignedUrl方法总是先触发,并且永远不会填充“fileSize”+“fileCreated”。
我认为我需要链接事件,因此getMetadata首先发生,但对Node(和Promises)来说相对较新,可以使用一些建议。
编辑每个BERGI的回复:(以下方法有效)
uploadFileToStorage(file) {
let utils = new Utils();
let newFileName = `${utils._guid()}-${Date.now()}`;
let bucket = admin.storage().bucket();
let filePath = url.format('audioFiles/' + newFileName);
let fileUpload = bucket.file(filePath);
let prom = new Promise(function(resolve, reject) {
if (!file) {
reject('No file provided');
return;
}
const blobStream = fileUpload.createWriteStream({
metadata: {
contentType: file.mimetype
}
});
blobStream.on('error', (error) => {
reject('Something is wrong! Unable to upload at the moment.');
return;
});
blobStream.on('finish', resolve);
blobStream.end(file.buffer);
}).then(() => {
return Promise.all([
fileUpload.getMetadata(),
fileUpload.getSignedUrl({
action: 'read',
expires: '03-09-2491'
}),
]);
}).then(([metadata, signedUrl]) => {
const fileSize = metadata[0].size;
const fileCreated = metadata[0].timeCreated;
const response = {
name: newFileName,
size: fileSize,
created: fileCreated,
url: signedUrl[0],
};
return response;
});
return prom;
}
答案 0 :(得分:2)
不要创建两个独立的承诺,也不要使用外部范围变量,这些变量在分配时永远不会知道。相反,使用Promise.all
等待多个承诺:
new Promise(resolve => {
blobStream.on('finish', resolve);
}).then(() => {
return Promise.all([
fileUpload.getMetadata(),
fileUpload.getSignedUrl({
action: 'read',
expires: '03-09-2491'
}),
]);
}).then(([metadata, signedUrl]) => {
const fileSize = metadata[0].size;
const fileCreated = metadata[0].timeCreated;
const response = {
name: newFileName,
size: fileSize,
created: fileCreated,
url: signedUrl[0],
});
return response;
});