我的目标是以json字符串的形式从谷歌驱动器文件夹及其子文件夹中获取文件列表。这样我就可以使用express将其公开为API端点，其他应用程序可以连接到它
代码正在工作。我得到了我想要的一切，但我不知道如何将我的数据变量导出到app.js
// get-filelist.js
var GoogleTokenProvider = require("refresh-token").GoogleTokenProvider,
request = require('request'),
async = require('async'),
data
const CLIENT_ID = "514...p24.apps.googleusercontent.com";
const CLIENT_SECRET = "VQs...VgF";
const REFRESH_TOKEN = "1/Fr...MdQ"; // get it from: https://developers.google.com/oauthplayground/
const FOLDER_ID = '0Bw...RXM';
async.waterfall([
//-----------------------------
// Obtain a new access token
//-----------------------------
function(callback) {
var tokenProvider = new GoogleTokenProvider({
'refresh_token': REFRESH_TOKEN,
'client_id': CLIENT_ID,
'client_secret': CLIENT_SECRET
});
tokenProvider.getToken(callback);
},
//-----------------------------
// connect to google drive, look for the folder (FOLDER_ID) and list its content inclusive files inside subfolders.
// return a list of those files with its Title, Description, and view Url.
//-----------------------------
function(accessToken, callback) {
// access token is here
console.log(accessToken);
// function for token to connect to google api
var googleapis = require('./lib/googleapis.js');
var auth = new googleapis.OAuth2Client();
auth.setCredentials({
access_token: accessToken
});
googleapis.discover('drive', 'v2').execute(function(err, client) {
getFiles()
function getFiles(callback) {
retrieveAllFilesInFolder(FOLDER_ID, 'root' ,getFilesInfo);
}
function retrieveAllFilesInFolder(folderId, folderName, callback) {
var retrievePageOfChildren = function (request, result) {
request.execute(function (err, resp) {
result = result.concat(resp.items);
var nextPageToken = resp.nextPageToken;
if (nextPageToken) {
request = client.drive.children.list({
'folderId': folderId,
'pageToken': nextPageToken
}).withAuthClient(auth);
retrievePageOfChildren(request, result);
} else {
callback(result, folderName);
}
});
}
var initialRequest = client.drive.children.list({
'folderId': folderId
}).withAuthClient(auth);
retrievePageOfChildren(initialRequest, []);
}
function getFilesInfo(result, folderName) {
result.forEach(function (object) {
request = client.drive.files.get({
'fileId': object.id
}).withAuthClient(auth);
request.execute(function (err, resp) {
// if it's a folder lets get it's contents
if(resp.mimeType === "application/vnd.google-apps.folder"){
retrieveAllFilesInFolder(resp.id, resp.title, getFilesInfo);
}else{
/*if(!resp.hasOwnProperty(folderName)){
console.log(resp.mimeType);
}*/
url = "http://drive.google.com/uc?export=view&id="+ resp.id;
html = '<img src="' + url+ '"/>';
// here do stuff to get it to json
data = JSON.stringify({ title : resp.title, description : resp.description, url : url});
//console.log(data);
//console.log(resp.title);console.log(resp.description);console.log(url);
//.....
}
});
});
}
});
}
]);
// export the file list as json string to expose as an API endpoint
console.log('my data: ' + data);
exports.files = function() { return data; };
在我的应用程序.js中，我使用这个
// app.js
var jsonData = require('./get-filelist');
console.log('output: ' + jsonData.files());
在检查函数getFilesInfo（）内部的输出时，app.js中的数据变量不包含任何数据。
那么，如何在其他脚本中访问我的数据变量呢？
同步/异步行为出现问题。
当调用从get-filelist导出的files（）函数时，app.js应该注意。这里的代码在需要get-filelist模块后立即调用files（）函数。此时，data变量仍然为空。
最好的解决方案是为files（）函数提供一个回调，该回调将在加载data变量后触发。
当然，你需要一些额外的东西：
loaded标志，以便您知道是立即触发回调（如果data已经加载）还是在加载完成后推迟触发- 用于等待将在加载时触发的回调的数组（
callbacks）
// get-filelist.js
var GoogleTokenProvider = require("refresh-token").GoogleTokenProvider,
request = require('request'),
async = require('async'),
loaded = false, //loaded? Initially false
callbacks = [], //callbacks waiting for load to finish
data = [];
const CLIENT_ID = "514...p24.apps.googleusercontent.com";
const CLIENT_SECRET = "VQs...VgF";
const REFRESH_TOKEN = "1/Fr...MdQ"; // get it from: https://developers.google.com/oauthplayground/
const FOLDER_ID = '0Bw...RXM';
async.waterfall([
//-----------------------------
// Obtain a new access token
//-----------------------------
function(callback) {
var tokenProvider = new GoogleTokenProvider({
'refresh_token': REFRESH_TOKEN,
'client_id': CLIENT_ID,
'client_secret': CLIENT_SECRET
});
tokenProvider.getToken(callback);
},
//-----------------------------
// connect to google drive, look for the folder (FOLDER_ID) and list its content inclusive files inside subfolders.
// return a list of those files with its Title, Description, and view Url.
//-----------------------------
function(accessToken, callback) {
// access token is here
console.log(accessToken);
// function for token to connect to google api
var googleapis = require('./lib/googleapis.js');
var auth = new googleapis.OAuth2Client();
auth.setCredentials({
access_token: accessToken
});
googleapis.discover('drive', 'v2').execute(function(err, client) {
getFiles()
function getFiles(callback) {
retrieveAllFilesInFolder(FOLDER_ID, 'root' ,getFilesInfo);
}
function retrieveAllFilesInFolder(folderId, folderName, callback) {
var retrievePageOfChildren = function (request, result) {
request.execute(function (err, resp) {
result = result.concat(resp.items);
var nextPageToken = resp.nextPageToken;
if (nextPageToken) {
request = client.drive.children.list({
'folderId': folderId,
'pageToken': nextPageToken
}).withAuthClient(auth);
retrievePageOfChildren(request, result);
} else {
callback(result, folderName);
}
});
}
var initialRequest = client.drive.children.list({
'folderId': folderId
}).withAuthClient(auth);
retrievePageOfChildren(initialRequest, []);
}
function getFilesInfo(result, folderName) {
data = []; //data is actually an array
result.forEach(function (object) {
request = client.drive.files.get({
'fileId': object.id
}).withAuthClient(auth);
request.execute(function (err, resp) {
// if it's a folder lets get it's contents
if(resp.mimeType === "application/vnd.google-apps.folder"){
retrieveAllFilesInFolder(resp.id, resp.title, getFilesInfo);
}else{
/*if(!resp.hasOwnProperty(folderName)){
console.log(resp.mimeType);
}*/
url = "http://drive.google.com/uc?export=view&id="+ resp.id;
html = '<img src="' + url+ '"/>';
// here do stuff to get it to json
data.push(JSON.stringify({ title : resp.title, description : resp.description, url : url}));
//console.log(resp.title);console.log(resp.description);console.log(url);
//.....
}
});
});
//console.log(data); //now, that the array is full
//loaded is true
loaded = true;
//trigger all the waiting callbacks
while(callbacks.length){
callbacks.shift()(data);
}
}
});
}
]);
// export the file list as json string to expose as an API endpoint
console.log('my data: ' + data);
exports.files = function(callback) {
if(loaded){
callback(data);
return;
}
callbacks.push(callback);
};
现在app.js的行为需要改变：
// app.js
var jsonData = require('./get-filelist');
jsonData.files(function(data){
console.log('output: ' + data);
});
/* a much more elegant way:
jsonData.files(console.log.bind(console,'output:'));
//which is actually equivalent to
jsonData.files(function(data){
console.log('output: ',data); //without the string concatenation
});
*/