Question

我尝试在Sails.js中将Youtube Data API与Node.js连接，但我对“fs.readFile”函数有疑问。

当我启动服务时，它返回“undefined”。

以下是我的YoutubeService代码：

module.exports = {

callYoutubeApi: function (req, res) {
    // Load client secrets from a local file.
    fs.readFile('api/services/client_secret.json', function processClientSecrets(err, content) {
        if (err) {
            sails.log('Error loading client secret file: ' + err);
            return "error";
        }
        // Authorize a client with the loaded credentials, then call the YouTube API.
        sails.log('123');
        return YoutubeService.authorize(JSON.parse(content), YoutubeService.getChannel);
    });
},   

`/**
 * Create an OAuth2 client with the given credentials, and then execute the
 * given callback function.
 *
 * @param {Object} credentials The authorization client credentials.
 * @param {function} callback The callback to call with the authorized client.
 */
authorize: function (credentials, callback) {
    var clientSecret = credentials.installed.client_secret;
    var clientId = credentials.installed.client_id;
    var redirectUrl = credentials.installed.redirect_uris[0];
    var auth = new googleAuth();
    var oauth2Client = new auth.OAuth2(clientId, clientSecret, redirectUrl);

    // Check if we have previously stored a token.
    fs.readFile(TOKEN_PATH, function (err, token) {
        if (err) {
            sails.log('tata');
            getNewToken(oauth2Client, callback);
        } else {
            sails.log('tonton');
            oauth2Client.credentials = JSON.parse(token);
            callback(oauth2Client);
        }
    });
},

/**
 * Get and store new token after prompting for user authorization, and then
 * execute the given callback with the authorized OAuth2 client.
 *
 * @param {google.auth.OAuth2} oauth2Client The OAuth2 client to get token for.
 * @param {getEventsCallback} callback The callback to call with the authorized
 *     client.
 */
getNewToken: function (oauth2Client, callback) {
    var authUrl = oauth2Client.generateAuthUrl({
        access_type: 'offline',
        scope: SCOPES
    });
    sails.log('Authorize this app by visiting this url: ', authUrl);
    var rl = readline.createInterface({
        input: process.stdin,
        output: process.stdout
    });
    rl.question('Enter the code from that page here: ', function (code) {
        rl.close();
        oauth2Client.getToken(code, function (err, token) {
            if (err) {
                sails.log('Error while trying to retrieve access token', err);
                return;
            }
            sails.log('getNewToken');
            oauth2Client.credentials = token;
            storeToken(token);
            callback(oauth2Client);
        });
    });
},

/**
 * Store token to disk be used in later program executions.
 *
 * @param {Object} token The token to store to disk.
 */
storeToken: function (token) {
    try {
        fs.mkdirSync(TOKEN_DIR);
    } catch (err) {
        if (err.code != 'EEXIST') {
            throw err;
        }
    }
    fs.writeFile(TOKEN_PATH, JSON.stringify(token));
    sails.log('Token stored to ' + TOKEN_PATH);
},

/**
 * Lists the names and IDs of up to 10 files.
 *
 * @param {google.auth.OAuth2} auth An authorized OAuth2 client.
 */
getChannel: function (auth) {
    var service = google.youtube('v3');
    service.channels.list({
        auth: auth,
        part: 'snippet,contentDetails,statistics',
        id: 'UCQznUf1SjfDqx65hX3zRDiA'
    }, function (err, response) {
        if (err) {
            sails.log('The API returned an error: ' + err);
            return;
        }
        var channels = response.items;
        if (channels.length == 0) {
            sails.log('No channel found.');
        } else {
            sails.log(channels[0]);
            return channels[0];
        }
    });
}
}`

控制器中的呼叫：

channelData = YoutubeService.callYoutubeApi();
sails.log(channelData);

错误：

debug: undefined
debug: 123

我认为调用无效，无法读取“processClientSecrets”函数。

如果有人有意帮助我，谢谢！

Answer 1

您已经创建了一个异步服务函数，但是您正在同步调用它。如果您不确定这意味着什么，请使用谷歌搜索自己“使用Node.js进行异步编程” - 这将使您的生活更轻松！

在这种情况下，您需要更改助手的函数签名：

callYoutubeApi: function (req, res) {

为：

callYoutubeApi: function (cb) {

cb代表“回调”，它是您传入的函数，在异步代码完成时会被调用。无论您当前使用字面值调用return，都会返回对cb的调用。 Node中的约定是cb的第一个参数是可能发生的任何错误，或者是null或undefined。第二个参数是异步代码的结果。总而言之，你得到：

callYoutubeApi: function (cb) {
  // Load client secrets from a local file.
  fs.readFile('api/services/client_secret.json', function processClientSecrets(err, content) {
    if (err) {
      // Using "return" just prevents you from accidentally continuing in this function.
      return cb(err);
    }
    // Authorize a client with the loaded credentials, then call the YouTube API.
    // This assumes that "authorize" is synchronous call that returns a value.  
    var auth = YoutubeService.authorize(JSON.parse(content), YoutubeService.getChannel);
    return cb(undefined, auth);
  });
},

您可以在控制器中调用：

YoutubeService.callYoutubeApi(function(err, channelData) {
  if (err) { 
    return res.serverError(err); 
  }
  // Now do something with channelData...
});

Sails.js：从控制器调用youtube服务

1 个答案: