猫鼬中的UnhandledPromiseRejectionWarning [重复]

Question

我有这样的类别架构：

var category_article_Schema = new Schema({
    "article_id": { type: String, required: false, unique: false },
    "category": String,
    "article": { type: mongoose.Schema.Types.ObjectId, ref: 'article'},
});

var category_article_Schema = mongoose.model('category_article_Schema', category_article_Schema);
module.exports = category_article_Schema;

文章架构：

var articleSchema = new Schema({
    "title": { type: String, required: true, unique: false },
    "details": String,
    "username": { type: String, required: true, unique: false },
    "postImageUrl": String,
    "url": String,
    "categories": [String],
    "created_at": { type: Date, default: Date.now }
});

var article = mongoose.model('article', articleSchema);
module.exports = article;

当我尝试使用填充方法获取基于类别的文章时，出现异常：UnhandledPromiseRejectionWarning: Unhandled promise rejection

function getPostByCategory(req, res, next) {
    category_article_model.find({category: req.params.name})
    .populate('article')
    .exec()
    .then(function(err, articlesByCategory) {
        if(err) throw err;
        console.log(articlesByCategory);
    })
}

首先，错误的原因可能是什么？为什么？我尝试寻找答案，但在每种情况下问题都不同。

Answer 1

重构

function getPostByCategory(req, res, next) {
    category_article_model.find({category: req.params.name})
    .populate('article')
    .exec()
    .then(function(err, articlesByCategory) {
       if(err) throw err;
       console.log(articlesByCategory);
    })
}

到这里

function getPostByCategory(req, res, next) {
    category_article_model.find({category: req.params.name})
   .populate('article')
   .exec()
   .then(function(articlesByCategory) {
      console.log(articlesByCategory);
   })
   .catch(function (err){
      throw err; // or handle it
   })
}