LibTest/async/Future/forEach_A01_t01.dart

/*
 * Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 * for details. All rights reserved. Use of this source code is governed by a
 * BSD-style license that can be found in the LICENSE file.
 */
/**
 * @assertion Future forEach(Iterable input, Future f(element))
 * Perform an async operation for each element of the iterable, in turn.
 * Runs f for each element in input in order, moving to the next element
 * only when the Future returned by f completes.
 * @description Checks that async operations for each element of the iterable are
 * executed in turn.
 * @author kaigorodov
 */
import "../../../Utils/async_utils.dart";
import "../../../Utils/expect.dart";

import "dart:async";

List input=[0,1,2,3,4];
int N=input.length;

main() {
  List<Completer> completers=new List<Completer>(N);
  List<bool> completerTrace=new List<bool>(N);
  List<bool> operationTrace=new List<bool>(N);

  for (int k=0; k<N; k++) {
    completerTrace[k]=operationTrace[k]=false;
    completers[k] = new Completer();
  }
  
  Future ff(int element) {
    // check that previous future is completed
    if (element>1) {
       Expect.isTrue(completerTrace[element-1]);
    }
    // check that next element is not yet processed
    if (element+1<N) {
       Expect.isFalse(operationTrace[element+1]);
    }
    operationTrace[element]=true;
    return completers[element].future;
  }
  
  Future f = Future.forEach(input, ff);
  
  asyncStart();
  bool visited = false;
  f.then((fValue) {
    visited = true;
    asyncEnd();
  });
  
  runLater((){
    // make sure future f is not completed
    Expect.isFalse(visited);
    
    // complete the futures in reverse order
    for (int k=N-1; k>=0; k--) {
      completers[k].complete(k);
      completerTrace[k]=true;
    }
  });
}