javascript - 将附加信息传递给 Promise 错误处理程序

Question

我已经 promise 了 fbgraph nodeJS API 并使用它来测试功能。此功能将帖子发布到给定的 Facebook 群组，然后验证该帖子是否已正确通过并删除该帖子。此代码的目的是测试用户是否具有不同组数组的发帖权限。

当前使用 Bluebird 的 Promise 库和生成器实现的代码。

var examplePostId = 12345678910

facebookPoster = Promise.coroutine(function* (feedId) {

  var postResponse = yield graph.postAsync(feedId + '/feed', sampleData);
  var postId = postResponse.id
  var getResponse = yield graph.getAsync(postId)
  var returnedId = getResponse.id
  var postedSuccessfully = true // <-- This is what I want to reference in my error handler.
  var deleteResponse = yield graph.delAsync(postId)
  var getAfterDeleteResponse = yield graph.getAsync(postId) // I expect this to throw an error since the post should already be deleted
  return postId

})

facebookPoster(examplePostId).then(function(postId){
  console.log(postId);
}).catch(function(err){
  console.log(err); // How can I tell the handler that error is fine because postedSuccessfully is true?
})

我的问题是:FB 的 Graph API 极其不可靠。即使帖子实际上没有被删除，我仍然会收到成功回复(记录在此处:___)。

因此，在我的生成器中，我尝试第二次获取 postID 的信息，并预计它会崩溃。当我确实收到错误时，它会传递给我的处理程序并触发我的处理程序。这很好，但我希望能够引用 postsSuccessively bool 值来区分我期望收到的错误和意外的错误。

如何引用 postsSuccessively bool 值，或实现另一种优雅的方式来区分收到的错误？

Answer 1

也许我不太明白你想做什么，但生成器函数的好处之一是你可以在其中使用 try-catch-语句正如您所习惯的那样。

因此，您可以使用在文本中描述的方式进行操作

var facebookPoster = Promise.coroutine(function* (feedId) {
  try {
    var postId = (yield graph.postAsync(feedId + '/feed', sampleData)).id;
    var returnedId = (yield graph.getAsync(postId)).id;
    var postedSuccessfully = true;
    var deleteResponse = yield graph.delAsync(postId);
    var getAfterDeleteResponse = yield graph.getAsync(postId);
  } catch (e) {
    if (!postedSuccessfully) // ignore error, it's expected
      throw e;
  }
  return postId;
});

facebookPoster(12345678910).then(console.log.bind(console), console.error.bind(console));

但是我认为以下内容更清晰:

var facebookPoster = Promise.coroutine(function* (feedId) {
  var postId = (yield graph.postAsync(feedId + '/feed', sampleData)).id;
  var returnedId = (yield graph.getAsync(postId)).id;
  var deleteResponse = yield graph.delAsync(postId);
  try { // sometimes deleteResponse is wrong, so double-check
    var getAfterDeleteResponse = yield graph.getAsync(postId);
  } catch (e) {
    // ignore error, it's expected
  } finally {
    if (getAfterDeleteResponse)
      throw new Error("hey it's still there while it shouldn't be!");
  }
  console.log(postId);
});

facebookPoster(12345678910).catch(console.error.bind(console));

或者更好的是，通过使用 then(success, fail) pattern 来避免可怕的 try-catch-finally 事情:

  …
  // sometimes deleteResponse is wrong, so double-check
  var getAfterDeleteResponse = yield graph.getAsync(postId).then(function(post) {
    throw new Error("hey it's still there while it shouldn't be!");
  }, function ignoreExpectedError(){});
  …