javascript - Sequencing async operations followed by onResult call

Question

Fiddle: http://jsfiddle.net/smartdev101/eLxxpjp3/

Inside asyncAction function call, a promise has been created to sequence two async operations, getRecords and getTotal followed by a final call to onResult(data) on success or onFail(info) in case of exception.

how to get onResult call upon completion of two async operations?

asyncAction: function(url, params, resultFunction, faultFunction) {
    puremvc.asyncproxy.AsyncProxy.prototype.asyncAction.call(this, resultFunction, faultFunction);

    if(!params.id) { //get master
        var queryString = this.url.parse(url, true).query;
        var offset = queryString.offset ? Number(queryString.offset) : 0;
        var limit = queryString.limit ? Number(queryString.limit) : 20;

        var data = {rows: null, total: null};

        var self = this;
        this.getRecords(data, offset, limit)
        .then(function(data){return self.getTotal(data)})
        //.fail(function(error){self.onFault(error)})
        .done(function(data){self.onResult(data)})

    } else { //get detail
        this.getDetail(params.id);
    }
},

getRecords: function(data, offset, limit) {
    console.log('get records');
    var defer = this.q.defer();
    this.connection.query("SELECT title, name, company FROM speaker LIMIT ? OFFSET ?", [limit, offset], function(error, rows, fields){
        console.log('get records done');
        data.rows = rows;
        defer.resolve(data);
        //defer.reject("earlier");
    });
    return defer.promise;
},

getTotal: function(data) {
    console.log('get total');
    var defer = this.q.defer();

    this.connection.query("SELECT * FROM speaker", function(error, rows, fields) { //SQL_CALC_FOUND_ROWS later
        data.total = rows.length;
        console.log('get total done');
        defer.resolve(data);
        //defer.reject("just like that");
    });

    return defer.promise;
},

onResult: function(data) {
    console.log('on result');
    puremvc.asyncproxy.AsyncProxy.prototype.onResult.call(this, data);
},

onFault: function(info) {
    puremvc.asyncproxy.AsyncProxy.prototype.onFault.call(this, info);
}

Answer 1

It seems like this could be simplified. It seems like you just want these async operations to be performed synchronously. If you return the promise, the original promise in the chain will become the new promise. The final fail will catch the first promise to be rejected.

asyncAction: function(url, params, resultFunction, faultFunction) {
    puremvc.asyncproxy.AsyncProxy.prototype.asyncAction.call(this, resultFunction, faultFunction);

    if(!params.id) { //get master
        var queryString = this.url.parse(url, true).query;
        var offset = queryString.offset ? Number(queryString.offset) : 0;
        var limit = queryString.limit ? Number(queryString.limit) : 20;

        var data = {rows: null, total: null};

        var self = this;
        this.getRecords(data, offset, limit)
        .then(function(data) {
          return self.getTotal(data);
        })
        .then(this.onResult.bind(this))
        .fail(this.onFault);
    } else { //get detail
        this.getDetail(params.id);
    }
},

getRecords: function(data, offset, limit) {
    console.log('get records');
    var defer = this.q.defer();
    this.connection.query("SELECT title, name, company FROM speaker LIMIT ? OFFSET ?", [limit, offset], function(error, rows, fields){
        console.log('get records done');
        data.rows = rows;
        defer.resolve(data);
        //defer.reject("earlier");
    });
    return defer.promise;
},

getTotal: function(data) {
    console.log('get total');
    var defer = this.q.defer();

    this.connection.query("SELECT * FROM speaker", function(error, rows, fields) { //SQL_CALC_FOUND_ROWS later
        data.total = rows.length;
        console.log('get total done');
        defer.resolve(data);
        //defer.reject("just like that");
    });

    return defer.promise;
},

onResult: function(data) {
    console.log('on result');
    puremvc.asyncproxy.AsyncProxy.prototype.onResult.call(this, data);
},