返回承诺抛出错误承诺 [英] Return a Promise that promises to throw error

问题描述

我是相当新的使用的承诺，我主要是坚持直线上升回调。下面code发生在一个角服务被发现，但没有真正的问题那么多，它主要是关于如何创建一个承诺，承诺将抛出一定的误差。因此，这是它如何与回调发生被纳入，避免了问题：

I am fairly new to using promises, I mostly stick to straight up callbacks. The following code happens to be found in an Angular Service, but that doesn't really matter that much, it's mostly regards how to create a promise that will promise to throw a certain error. So this is how it would happen with callbacks being incorporated, which avoids the problem:

var client = algolia.Client('ApplicationID', 'apiKey');


var indices = {

    users: client.initIndex('users'),
    topics: client.initIndex('topics')

}

return {

   search: function(indexName, searchTerms, cb){
       var index = indices[indexName];

       if(index){
          index.search(searchTerms).then(function handleSuccess(msg){
               cb(null,msg);
            }, function handleError(err){
               cb(err);
            }
       }
       else{
          cb(new Error('no matching index'));
       }

   }

...但改变上述用纯承诺，我不知道该怎么做确切：

var client = algolia.Client('ApplicationID', 'apiKey');

var indices = {

    users: client.initIndex('users'),
    topics: client.initIndex('topics')

}

return {

   search: function(indexName, searchTerms){
       var index = indices[indexName];

       if(index){
          return index.search(searchTerms); //returns a promise
       }
       else{
          //if there is no matching index, how can I return a promise then will return an error?
       }

   }

我知道有很多不同的方法来构造code，以避免在手头的问题，但我很好奇，如果有办法直接解决这个问题。

I know there are different ways to structure the code to avoid the problem at hand but I am curious if there is way to solve it directly.

推荐答案

您可以注入 $ Q 服务，并返回 $ q.reject（原因），例如：

You could inject $q service and return $q.reject(reason), e.g:

return $q.reject('NO_INDEX');

$ Q文档：

创建与指定的理由拒绝了解决的承诺。

Creates a promise that is resolved as rejected with the specified reason.

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