蓝鸟承诺：捕捉错误

Question

在 Bluebird 的 promise 库的帮助下，我在 Facebook 的 Graph API 上使用请求模块。通过传入错误的密钥来测试 catch 方法。

这里有两个问题： 1、为什么我用promise的时候response是一个数组？ 2. 为什么根本没有调用 clientError 谓词？

var request = Promise.promisifyAll(require('request'));
var queryObj = {
    client_id: config.client_id,
    redirect_uri: config.redirect_uri,
    client_secret: config.wrong_client_secret,
    code: req.query.code
};

var reqObj = {
    url: 'https://graph.facebook.com/v2.3/oauth/access_token',
    qs: queryObj
};

request.getAsync(reqObj)
    .then(function (contents) {
        console.log('success ' + JSON.stringify(contents));
/*
Produces (simplified it for brevity)
[{"statusCode":400,"body":"{\"error\":{\"message\":\"Error validating client secret.\"}}"}]
*/

    }).catch(clientError, function(e) {
        console.log('error: ' + e);
    });

function clientError(contents) { // this is not called at all
    var statusCode = contents[0].statusCode;
    console.log('checking for error...' + statusCode);

    return statusCode >= 400 && statusCode < 500;
}

// without promise: 
var request = require('request');

request(reqObj, function (error, response, body) {
        if (!error && response.statusCode == 200) {
            console.log(JSON.stringify(response));
/* Response: (simplified it for brevity)
{"statusCode":400,"body":"{\"error\":{\"message\":\"Error validating client secret.\"}}"}
*/
        } else {
            console.log(JSON.stringify(response));
        }
    });

Answer 1

Why is the response in an array when I use promise?

因为 request 库通过使用多个参数解析回调违反了回调约定。 Bluebird 没办法，只能用数组包裹起来。您可以轻松 .get(0) 或 .get(1) 以访问特定的属性.

request.getAsync("...").get(0); // just the response
request.getAsync("...").spread(function(response, body){ // spread arguments
      // ...
});

Why is the clientError predicate is not being called at all?

因为promise没有处于异常状态，之前的promiseresolved和then回调运行.

蓝鸟承诺：捕捉错误

Bluebird promise: catching errors

javascript

promise

facebook-graph-api

bluebird