Promise

Concurrently executes several promises and returns another promise that is fulfilled when the original promises are fulfilled. The resolved value is an array containing the values of the original promises in the original order (not the order they were fulfilled).

If one of the original promises fail, the returned promise will be rejected with the same reason.

 import Felgo
 import QtQuick

 App {
   Component.onCompleted: {
     var p1 = Promise.resolve(3);
     var p2 = 1337;
     var p3 = HttpRequest
             .get("http://httpbin.org/get")
             .then(function(resp) {
                 return resp.body;
             });

     var p4 = Promise.all([p1, p2, p3]);

     p4.then(function(values) {
         console.log(values[0]); // 3
         console.log(values[1]); // 1337
         console.log(values[2]); // resp.body
     });
   }
 }

Creates a new Promise object.

Since the Javascript engine in QML does not allow us to expose new types with constructors, the new Promise(executor) syntax is not supported. Instead the create function can be used:

 import Felgo
 import QtQuick

 App {
   Component.onCompleted: {

     var p = Promise.create(function(resolve, reject) {
       // handle asynchronous code here
       // e.g. with asynchronous HttpRequest
       HttpRequest
         .get("http://httpbin.org/get")
         .timeout(5000)
         .end(function (err, res) {
           if(res.ok)
             resolve(res.body)
           else
             reject(err.message)
         })
     });

     // execute promise and handle result
     p.then(function(value) {
        // success
       console.log("Value: "+JSON.stringify(value))
     }).catch(function(reason) {
       // failure
       console.log("Error: "+reason)
     });

   }
 }

Concurrently executes several promises and returns another promise that is fulfilled when the first of those promises is fulfilled.

 import Felgo
 import QtQuick

 App {
   Component.onCompleted: {
     var p1 = HttpRequest
          .get("http://httpbin.org/delay/3")
          .then(function(resp) {
              return 3;
          });

     var p2 = HttpRequest
         .get("http://httpbin.org/delay/1")
         .then(function(resp) {
             return 1;
         });

     var p3 = Promise.race([p1, p2]);

     p3.then(function(value) {
         console.log(value); // 1 or 3
     });
   }
 }

Returns a rejected promise.

 import Felgo
 import QtQuick

 App {
   Component.onCompleted: {
     var p = Promise.reject("error");

     p.catch(function(reason) {
         console.log(reason); // "error"
     });
   }
 }

Returns a resolved promise.

 import Felgo
 import QtQuick

 App {
   Component.onCompleted: {
     var p = Promise.resolve(5);

     p.then(function(value) {
         console.log(value); // 5
     });
   }
 }