mongodb - Node.js + Mongoose 让 Model.find 方法同步执行

Question

我在用 Node.js + Mongoose + MongoDB 开发一个小程序，其中有一个操作是这样的：

function get( query ){
    query = query||null;
    if( query === null ){
        return this.model.find( {}, function( err, docs ){
            return docs;
        });
    }else{
        return this.model.find( query, function( err, docs ){
            return docs;
        }
    }
}

目标：get 是我用来读取 Collection 里面的文档的，query 是查询条件，如果没有传入查询条件，则返回整个 Collection；如果传入了查询条件，则按条件查询。

错误：因为 this.model.find方法是异步的，在find返回查询结果之前，get函数已经return了，所以我总是得到undefined。

请问有什么办法能让get得到find的返回值吗？

Answer 1

The entire design idea of ​​nodejs is asynchronous, don’t write with synchronous thinking.

var url=require('url');
function get(query,callback){
    query=query||{};
    this.model.find(query,callback);
}

httpServer.on('request',function(req,res){
    var query=url.parse(req.url, true).query;

    get(query,function(err,doc){
        if(err){
            res.end(err);
            return;
        }

        res.end(doc)
    })
})

Answer 2

It is best to use callbacks for asynchronous requests

function get( query,callback ){
    query = query||{};
    this.model.find( query, function( err, docs ){
         callback(null, docs);
    });
}

When query is empty, the entire collection is returned

Answer 3

You can use libraries such as Q and Step to force query synchronization.

In fact, most people do need synchronization methods when writing tests. I also specifically asked the author of Mongoose, but he felt it was not necessary. . .