then语句中的异步Mongoose回调 [英] Async Mongoose callbacks in then statement

问题描述

我在使用来自Mongoose

这是我的代码

 req.checkBody(BookManager.SCHEME);
        req.getValidationResult()
            .then(function (result) {
                if (!result.isEmpty()) {
                    handler.onError('Invalid payload');
                    return;
                }
                return new BookModel({
                    author: data.author,
                    name: data.name,
                    year: data.year
                });
            })
           .then((book) => {
            BookModel.find({name: book.name}, function (err, docs) {
                if (docs.length) {
                    throw new Error("Book already exists");
                } else {
                    return book;
                }
            });
            })
            .then((book) => {
                book.save();
            })
            .then((saved) => {
                handler.onSuccess(saved);
            })
            .catch((error) => {
                handler.onError(error.message);
            });

从上面的代码中可以看到.我正在检查这种书是否已经存在，为了做到这一点，我使用了异步查找方法，该方法在主要的程序计数器"进一步执行之后被调用.

As you can see from the code above. I am checking whether such book already exists and in order to do this I use async find method that is called after the main "program counter" has gone further.

我该如何解决这个问题?

How can I solve this problem ?

还请告诉我我是否选择了合适的等待时间来实现我的用例?也许我做错了，还有其他一些最佳实践可以解决这个问题.

Also please tell me whether I have chosen the right wait to implement my use case ? Maybe I am doing it wrong and there are some other best practices to handle this.

推荐答案

我相信您的第二个then(..)应该看起来像这样:

I believe your second then(..) should look more like this:

.then(function(book){
    return new Promise(function(resolve, reject){
        BookModel.find({ name: book.name }, function(err, docs) {
            if (docs.length) {
                reject({message: "Book already exists"});
            } else {
                resolve(book);
            }
        });
    });
})

这篇关于then语句中的异步Mongoose回调的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！