Question

我正在使用'clouddns'模块将~800个域名导入Rackspace帐户。我一直收到错误说明以下

TypeError: Cannot call method 'forEach' of undefined
at _wrapDomains (/home/duet/www/git/node-rackspace/node_modules/clouddns/lib/clouddns/core.js:146:17)
at /home/duet/www/git/node-rackspace/node_modules/clouddns/lib/clouddns/core.js:209:14
at Request._callback (/home/duet/www/git/node-rackspace/node_modules/clouddns/lib/clouddns/common.js:170:5)
at Request.self.callback (/home/duet/www/git/node-rackspace/node_modules/clouddns/node_modules/request/main.js:120:22)
at Request.EventEmitter.emit (events.js:98:17)
at Request.<anonymous> (/home/duet/www/git/node-rackspace/node_modules/clouddns/node_modules/request/main.js:555:16)
at Request.EventEmitter.emit (events.js:95:17)
at IncomingMessage.<anonymous> (/home/duet/www/git/node-rackspace/node_modules/clouddns/node_modules/request/main.js:517:14)
at IncomingMessage.EventEmitter.emit (events.js:117:20)
at _stream_readable.js:920:16

在查看有问题的库文件（core.js）之后，我决定在那里抛出一些日志语句，看看我是否能弄清楚发生了什么。这是代码：

CloudDNS.prototype.getDomains = function getDomains(options, callback) {
    var args = Array.prototype.slice.call(arguments),
        callback = args[args.length - 1];

    if (typeof callback !== 'function') {
        throw new Error("This method requires a callback");
    }

    var self = this;
    var reqOpts = {
        method: 'GET',
        uri: this.dnsUrl('domains'),
        client: this
    }

    if ((arguments.length > 1) && (typeof arguments[0] === 'object')) {
        reqOpts.params = {
            name: args[0]
        }
    }

    this.rackspace(reqOpts, callback, function(body) {
        var result = JSON.parse(body);
        console.log(result.domains); //good here, it's an array and I can even forEach on it!
        self._wrapDomains(result.domains, callback); //undefined wtf?
        console.log(result.domains); //same as before, works brilliantly
    });
};

CloudDNS.prototype._wrapDomains = function _wrapDomains(domainArray, callback) {
    var self = this;
    var results = [];

    console.log(domainArray); //reports undefined

    domainArray.forEach(function(domain) {
        results.push(new(clouddns.Domain)(self, domain));
    });

    return callback(null, results);
}

由于result.domains是在方法被调用之前和之后定义的，所以我被强调了，但在该方法中它是'undefined'。任何人都可以解释为什么会发生这种情况吗？

Answer 1

我只是在github上查看源代码。如果查看堆栈跟踪中的第二行，则为at /home/duet/www/git/node-rackspace/node_modules/clouddns/lib/clouddns/core.js:209:14

所以_wrapDomains在createDomain方法（第209行）中被调用到文件的末尾。如果你在那里调查，你会发现它为什么用空值来调用它。

传递给函数时Node.js'undefined'变量

1 个答案: