CODEWITHSUNDEEP
javascriptnode.jsbluebird
Vibhas
Vibhas

Reputation: 261

Using result of one function to call other in bluebird promises

I am working on nodejs and converting my model callbacks to promises as much as possible by keeping response data same to controller so that I don’t need to change controller logic.So I need to use callbacks which I know is a bad idea while working with bluebird.

 var functions={ 
              checkifexists:function(data){
              return new Promise(function(resolve,reject){
                // Query is fired here  
                resolve(data) or reject (data) 
              }); 
            },
             create:function(data,cb{
              mysql.getConnectionFromPool(function(err,connection){
              this.checkifexists(data,connection).then(function(res){
                if(res.count)
                 {
                    cb(res.count);
                }
                else
                {
                    connection.query(insertsql,data,function(err,data){
                         // Handle any error or return insertID
                           cb(null,insertID)
                    });
                }
            }).catch(function(e){
                console.log(e);
            }).finally(function(){
                connection.release();
            });
        });}

Based on accepted answer Sample Controller Code:

 sampleModel.create(req.body,function(err,result){
    console.log("Err : "+err); // Always Null
    console.log("Result :"+result); // Always displays both reject and resolve cases
});

In above code there is one checkifexists function and a create function but from controller only create function is called so I adjusted by code accordingly but still it looks messy.

Is it the right way to do it ? What if I need to call series of function but one after another so that I may pass response of one function to another and so on .

Upvotes: 0

Views: 123

Answers (1)

Bergi
Bergi

Reputation: 664538

Instead of dealing manually with callbacks you should use asCallback. Promisify your node-style connection things, and use promises wherever you can.

var functions = {
    getConnection: function() {
        return Promise.fromCallback(mysql.getConnectionFromPool.bind(mysql))
        .disposer(function(connection) {
            connection.release();
        });
    },
    checkifexists: function(data, connection) {
        return new Promise(function(resolve,reject) {
            // Query is fired here  
            resolve(data) or reject (data) 
        }); 
    },
    insert: function(data, connection) {
        return Promise.fromCallback(connection.query.bind(connection, insertsql, data));
    },
    create: function(data, cb) {
        return Promise.using(this.getConnection(), function(connection) {
            return this.checkifexists(data, connection)
            .then(function(res) {
                if (res.count) {
                    throw res.count; // are you sure?
                } else {
                    return this.insert(data, connection);
                }
            }.bind(this))
        }.bind(this))
        .asCallback(cb); // this is all you need
    });
};

Upvotes: 1

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