使用不同的变量多次异步运行某些代码

所以，我正在尝试让我的应用程序读取HealthKit数据。我有一个从主应用程序视图控制器调用的函数，该函数会导致在另一个类中查询该月的所有健康数据。然后，在将数据数组从计算类中的单独函数返回到视图控制器中的单独函数之前，需要进行一些计算。

由于数据量大，每次查询大约需要 2 秒。我希望能够异步设置它们，当它们全部返回时，我可以更新 UI。

问题是，我为每个月调用函数，该函数去并启动HKSampleQueries，但它们不会按顺序返回，并且它们返回所需的时间各不相同。这意味着我最终会在一组数据计算中途更改变量，因为下一组数据计算刚刚开始。

我只知道两种方法：

在调用每个计算之前设置延迟，如下所示：

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 3 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{}

但这浪费了应用程序时间

或者我可以多次复制代码并为每个月调用不同的类。但这似乎是愚蠢和低效的。

所以问题是。如何有效地共享每次使用不同变量运行多次的代码。干杯

函数示例：

在视图控制器中：

HeartRateCalculator *commonClassTwo =[[HeartRateCalculator alloc] init];
[commonClassTwo calculateData:0];
[commonClassTwo calculateData:-1];
[commonClassTwo calculateData:-2];

在心率计算器中

-(void)calculateData:(NSInteger)monthsBack{
  //Some other stuff
//Generate monthPeriodPredicate based on monthsBack integer
  HKSampleQuery *query = [[HKSampleQuery alloc] initWithSampleType:heartRate predicate:monthPeriodPredicate limit:200000 sortDescriptors:@[timeSortDescriptor] resultsHandler:^(HKSampleQuery *query, NSArray *results, NSError *error) {
  //Finish Calculations, call other functions (ie. [self doThis];) and then return
//When calculations return, monthPeriodPredicate is always value of the last predicate to be called, not the one that the HKSampleQuery was made with.
}
[healthStoreFive executeQuery:query];

完整代码：

-(void)calculateData:(NSInteger)monthsBack withCompletionBlock:(void(^)())completionBlock {//0 Means only current month, 2 means this month and last month and month before
//for(NSInteger i=0; i>=monthsBack; i--){
    //monthForCalculation = monthsBack;
    NSDateComponents *components = [[NSCalendar currentCalendar] components: NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond fromDate:[NSDate date]];
    NSDateComponents *adjustableComponent = [[NSDateComponents alloc] init];
    [adjustableComponent setMonth:monthsBack];
    [adjustableComponent setDay:-[components day]+1];
    [adjustableComponent setHour:-[components hour]];
    [adjustableComponent setMinute:-[components minute]];
    [adjustableComponent setSecond:-[components second]];
    startOfMonth = [[NSCalendar currentCalendar] dateByAddingComponents:adjustableComponent toDate:[NSDate date] options:0];
    adjustableComponent = [[NSDateComponents alloc] init];
    [adjustableComponent setMonth:1];
    NSDate *endOfMonth = [[NSCalendar currentCalendar] dateByAddingComponents:adjustableComponent toDate:startOfMonth options:0];
    NSDate *secondEarlier = [endOfMonth dateByAddingTimeInterval:-1];
    components = [[NSCalendar currentCalendar] components: NSCalendarUnitDay fromDate:secondEarlier];
    daysInMonth = [components day];
    NSPredicate *monthPeriodPredicate = [HKQuery predicateForSamplesWithStartDate:startOfMonth endDate:endOfMonth options:HKQueryOptionStrictStartDate];
    healthStoreFive = [[HKHealthStore alloc] init];
    HKQuantityType *heartRate = [HKObjectType quantityTypeForIdentifier:HKQuantityTypeIdentifierHeartRate];
    NSSortDescriptor *timeSortDescriptor = [[NSSortDescriptor alloc] initWithKey:HKSampleSortIdentifierEndDate ascending:NO];
    HKSampleQuery *query = [[HKSampleQuery alloc] initWithSampleType:heartRate predicate:monthPeriodPredicate limit:200000 sortDescriptors:@[timeSortDescriptor] resultsHandler:^(HKSampleQuery *query, NSArray *results, NSError *error) {
        NSMutableArray *dataValues = [[NSMutableArray alloc] init];
        NSMutableArray *dataDates = [[NSMutableArray alloc] init];
        for (HKQuantitySample *sample in results) {
            [dataValues addObject:[NSNumber numberWithFloat:[sample.quantity doubleValueForUnit:[[HKUnit countUnit] unitDividedByUnit:[HKUnit minuteUnit]]]]];
            [dataDates addObject:sample.startDate];
        }
        monthForCalculation = monthsBack;
        chronologicalDataValues = [[NSMutableArray alloc] init];
        chronologicalDataDates = [[NSMutableArray alloc] init];
        chronologicalDataValues = [[[dataValues reverseObjectEnumerator] allObjects] mutableCopy];
        chronologicalDataDates = [[[dataDates reverseObjectEnumerator] allObjects] mutableCopy];          
        //dispatch_async(dispatch_get_main_queue(), ^{
            if(dataDates.count == 0){
                ViewController *commonClass =[[ViewController alloc] init];
                [commonClass receiveCalculationData:[[NSMutableArray alloc] init] array:[[NSMutableArray alloc] init] daysToDisplay:[[NSMutableArray alloc] init] chosenMonth:monthForCalculation];
            }
            else{
                NSLog(@"%@", [dataDates objectAtIndex:dataDates.count-1]);
                NSLog(@"%@", [dataDates objectAtIndex:0]);
                [self calculateDayStringsFromData];
            }
            completionBlock();
        //});
    }];
    NSLog(@"HKSampleQuery Requested For Heart Rate Data");
    [healthStoreFive executeQuery:query];

//} }

您可以使用

dispatch_group来安排在所有任务完成后触发块。

您只需要修改calculateData:方法即可接受dispatch_group_t参数(如果需要，您也可以随时添加完成块(：

- (void)calculateData:(NSInteger)monthsBack group:(dispatch_group_t)group {
    dispatch_group_enter(group); // increment group task count
    //Some other stuff
    HKSampleQuery *query = [[HKSampleQuery alloc] initWithSampleType:heartRate predicate:monthPeriodPredicate limit:200000 sortDescriptors:@[timeSortDescriptor] resultsHandler:^(HKSampleQuery *query, NSArray *results, NSError *error) {
        //Finish Calculations, call other functions (ie. [self doThis];) and then return
        dispatch_group_leave(group); // decrement task count
    }];
    [healthStoreFive executeQuery:query];
}

然后你可以这样称呼它：

HeartRateCalculator *commonClassTwo =[[HeartRateCalculator alloc] init];
dispatch_group_t group = dispatch_group_create();
[commonClassTwo calculateData:0 group:group];
[commonClassTwo calculateData:-1 group:group];
[commonClassTwo calculateData:-2 group:group];
dispatch_group_notify(group, dispatch_get_main_queue(), ^{ // called when all tasks are finished.
    // update UI
});

这与 Warif 的原理相同，但dispatch_groups比使用自己的变量来跟踪执行的任务数量要优雅得多。

虽然我不确定你说你想异步执行任务是什么意思。来自 HKSampleQuery 年的苹果文档：

查询在匿名后台队列上运行。

因此，您的任务已经是异步的。

使用 block

[commonClassTwo calculateData:0 withCompletionBlock:^{
    [commonClassTwo calculateData:-1 withCompletionBlock:^{
        [commonClassTwo calculateData:-2 withCompletionBlock:^{
            NSLog(@"All 3 calculation done");
        }];
    }];
}];

- (void)calculateData:(NSInteger)monthsBack withCompletionBlock:(void(^)())completionBlock {
    //Some other stuff
    HKSampleQuery *query = [[HKSampleQuery alloc] initWithSampleType:heartRate predicate:monthPeriodPredicate limit:200000 sortDescriptors:@[timeSortDescriptor] resultsHandler:^(HKSampleQuery *query, NSArray *results, NSError *error) {
        //Finish Calculations, call other functions (ie. [self doThis];) and then return
        completionBlock();
    }
    [healthStoreFive executeQuery:query];
}

更新

对于异步调用，请有一个计数器integer。初始值将是您想要的异步调用数。(这里3(
在每个调用的完成块中，递减计数器并检查所有调用是否完成。
如果已完成，请更新UI。

[commonClassTwo calculateData:0 withCompletionBlock:^{
    // counter--;
    // [self updateUI];
}];
[commonClassTwo calculateData:-1 withCompletionBlock:^{
    // counter--;
    // [self updateUI];
}];
[commonClassTwo calculateData:-2 withCompletionBlock:^{
    // counter--;
    // [self updateUI];
}];

- (void)updateUI {
    // if counter == 0 {
    //     dispatch_async(dispatch_get_main_queue(), ^{
    //         update UI
    //     });
    // }
}

您可以改为创建单独的类并同时运行它们。

HeartRateCalculator *commonClassOne =[[HeartRateCalculator alloc] init];
HeartRateCalculator *commonClassTwo =[[HeartRateCalculator alloc] init];
HeartRateCalculator *commonClassThree =[[HeartRateCalculator alloc] init];
[commonClassOne calculateData:0];
[commonClassTwo calculateData:-1];
[commonClassThree calculateData:-2];

这样，您就不必复制代码，但它们不会覆盖同一类中的值。

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