An interface for implementing asynchronous execution of algorithms, similar to Promise in JavaScript.
timer.mqh - timer, just to demonstrate asynchronous execution

You can also Download using the npm package manager

npm i mql5-promise

Promise Example :

 #include "timer.mqh"
#include "index.mqh"

void OnInit () {
     new Promise(printAndTimoutResolve, "111" )
        .then(printAndReject, "222" ) // then - run if prev promise is resolved
        .ccatch(printAndResolve, "333" ) // ccatch - run if prev promise is rejected
        .ccatch(printAndResolve, "444" )
        .ccatch(printAndResolve, "555" )
        .then(printAndResolve, "666" )
        .finally(printAndResolve, "end" ) // finally - run anything
        .destroy(); // clear memory theese promises after executing all promises

     Print ( "start" );

     // printAndTimoutResolve 111 // timeout after Print
     // start
     // printAndReject 222
     // printAndTimoutResolve 333
     // printAndTimoutResolve 666
     // printAndTimoutResolve end
};

void promiseAllResolve( ulong promiseId, string &prevResult[], string parametr) {
     Print ( "promiseAllResolve " + parametr);
};

void printAndTimoutResolve( ulong promiseId, string prevResult, string parametr) {
     Print ( "printAndTimoutResolve " + parametr);
    Timer::setTimout(resolveByIdStr, 2000 , string (promiseId));
};
void resolveByIdStr( string id) { Promise::resolveById( ulong (id)); }

void printAndResolve( ulong promiseId, string prevResult, string parametr) {
     Print ( "printAndResolve " + parametr);
    Promise::resolveById(promiseId);
};

void printAndReject( ulong promiseId, string prevResult, string parametr) {
     Print ( "printAndReject " + parametr);
    Promise::rejectById(promiseId);
};

For example, Promise:all:

 void OnInit () {
    Promise* list1[] = {
         new Promise(printAndTimoutResolve, "Promise 1" )
            .then(printAndTimoutResolve, "Promise 1.1" )
        ,
         new Promise(printAndReject, "Promise 2" ),
         new Promise(printAndTimoutResolve, "Promise 3" ),
    };

    Promise::all(list1, promiseAllResolve) // resolve if all promises are resolved
        .then(printAndResolve, "Promise::all resolved" )
        .ccatch(printAndResolve, "Promise::all rejected" )
        .destroy(); // delete all promises

     // printAndTimoutResolve Promise 1
     // printAndReject Promise 2
     // printAndTimoutResolve Promise 3
     // printAndResolve Promise::all rejected
};

Promise example:race:

 void OnInit () {
    Promise* list2[] = {
         new Promise(printAndTimoutResolve, "Promise 1" )
            .then(printAndTimoutResolve, "Promise 1.1" )
        ,
         new Promise(printAndReject, "Promise 2" ),
         new Promise(printAndTimoutResolve, "Promise 3" ),
    };

    Promise::race(list2, printAndResolve, "Promise::race" ) // resolve/reject after the first promise
        .then(printAndResolve, "Promise::race resolved" )
        .ccatch(printAndResolve, "Promise::race rejected" )
        .destroy();

     // printAndTimoutResolve Promise 1
     // printAndReject Promise 2
     // printAndTimoutResolve Promise 3
     // Promise::race rejected
};

For example, Promise:any:

 void OnInit () {
    Promise* list3[] = {
         new Promise(printAndTimoutResolve, "Promise 1" )
            .then(printAndTimoutResolve, "Promise 1.1" )
        ,
         new Promise(printAndReject, "Promise 2" ),
         new Promise(printAndTimoutResolve, "Promise 3" ),
    };

    Promise::any(list3, printAndResolve, "Promise::any" )
        .then(printAndResolve, "Promise::any resolved" )
        .ccatch(printAndResolve, "Promise::any rejected" )
        .destroy();

     // printAndTimoutResolve Promise 1
     // printAndReject Promise 2
     // printAndTimoutResolve Promise 3
     // printAndResolve Promise::any
     // printAndResolve Promise::any resolved
};