在 iOS 中，我需要调用相同的方法次数，但应用程序必须等到方法完成它的第一个任务。（我不能使用 bool 值来检查函数是否正在运行）。
如何将请求排队或等到上一个任务完成？有没有办法可以使用 NSOperation 或 NSThread？
谢谢
这是我需要多次调用的方法
- (void)fetchJobs
{
dispatch_queue_t queueLocal = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_group_t groupLocal = dispatch_group_create();
UIApplication *app = [UIApplication sharedApplication];
NSTimeInterval backgroundTime = app.backgroundTimeRemaining;
NSLog(@"Background task remain time: %g seconds", (double)backgroundTime);
[[NSNotificationCenter defaultCenter] postNotificationName:@"UPLOAD_PROCESS_START" object:nil];
self.assetUpdateTaskID = [app beginBackgroundTaskWithExpirationHandler:^{
dispatch_async(dispatch_get_main_queue(), ^{
[self endTask];
});
}];
dispatch_group_async(groupLocal, queueLocal, ^{
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Files" inManagedObjectContext:self.managedObjectContext];
//Setup the fetch request
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entity];
NSPredicate *predicate = [NSPredicate predicateWithFormat: @"uploaded like %@", [NSString stringWithFormat:@"0"]];
[request setPredicate:predicate];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"timeStamp" ascending:YES];
[request setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];
NSError *error = nil;
//fetch the records and handle an error
NSArray *fetchResults = [self.managedObjectContext executeFetchRequest:request error:&error];
if (fetchResults == nil) {
NSLog(@"File Data fetching error : %@", [error localizedDescription]);
}
else{
if ([fetchResults count] > 0) {
dispatch_apply([fetchResults count], queue, ^(size_t i){
NSLog(@"Loop count %zu", i);
Files *file = [fetchResults objectAtIndex:i];
self.manageObjectForFiles = file;
NSLog(@"Fetched File details -> Name: %@ & status: %@" , file.fileName, file.uploaded);
BOOL uploaded = [self filePosting:file.fileName];
if (uploaded) {
[self.managedObjectContext deleteObject:file];
NSError *error;
if (![self.managedObjectContext save:&error]) {
NSLog(@"File table update error : %@", [error description]);
}
}
});
/*
for (int i = 0; i < [fetchResults count]; i++) {
}*/
}
}
dispatch_async(dispatch_get_main_queue(), ^{
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
int remainJobs = [self fetchFileTableCount];
if (remainJobs > 0) {
[UIApplication sharedApplication].applicationIconBadgeNumber = remainJobs;
[[NSNotificationCenter defaultCenter] postNotificationName:@"UPLOAD_REMAIN" object:nil];
}
else{
[UIApplication sharedApplication].applicationIconBadgeNumber = 0;
[[NSNotificationCenter defaultCenter] postNotificationName:@"UPLOAD_PROCESS_COMPLETED" object:nil];
NSLog(@"-----------------------------------------------");
NSLog(@"There are no more uploads");
NSLog(@"-----------------------------------------------");
}
[self endTask];
});
});
dispatch_release(groupLocal);
}