我正在构建的应用程序包含数千个项目的目录，这些项目需要存储在手机上。目前我正在通过 CoreData 实现这一点，因为从逻辑上讲，它似乎是放置它的最佳位置。我正在使用 GCD 在后台运行 CoreData 插入过程并显示进度条/当前完成百分比。这可以按预期工作，但是对于仅 5000 个项目，在 iPhone 4 上需要 8 分钟才能完成。此应用程序将在 3GS 及更高版本上使用，并且一旦启动，将更有可能包含 30/40,000 个项目。因此，这个处理时间将非常长。
有什么方法可以使用 CSV 文件或其他内容进行搜索，而不是将每个项目存储在 CoreData 中？我假设这样的方法会降低效率，但它会减轻过多的等待时间。除非有另一种解决方案可以帮助解决这个问题。
谢谢。
编辑：我不确定如何在整个操作结束时保存上下文，因为它在循环中使用单独的上下文。对此的任何建议将不胜感激。我不知道如何在这方面取得进展。
正在使用的插入代码
- (void) processUpdatesGCD {
NSArray *jsonArray=[NSJSONSerialization JSONObjectWithData:_responseData options:0 error:nil];
NSArray *products = [jsonArray valueForKey:@"products"];
NSArray *deletions;
if ([jsonArray valueForKey:@"deletions"] == (id)[NSNull null]){
self.totalCount = [products count];
} else {
deletions = [jsonArray valueForKey:@"deletions"];
self.totalCount = [products count] + [deletions count];
}
self.productDBCount = 0;
_delegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *managedObjectContext = _delegate.managedObjectContext;
self.persistentStoreCoordinator = [managedObjectContext persistentStoreCoordinator];
_managedObjectContext = managedObjectContext;
// Create a new background queue for GCD
dispatch_queue_t backgroundDispatchQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0);
for (id p in products) {
// id product = p;
// Dispatch the following code on our background queue
dispatch_async(backgroundDispatchQueue,
^{
id product = p;
// Because at this point we are running in another thread we need to create a
// new NSManagedContext using the app's persistance store coordinator
NSManagedObjectContext *backgroundThreadContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
[backgroundThreadContext setPersistentStoreCoordinator:self.persistentStoreCoordinator];
NSFetchRequest *BGRequest = [[NSFetchRequest alloc] init];
NSLog(@"Running.. (%@)", product);
[BGRequest setEntity:[NSEntityDescription entityForName:@"Products" inManagedObjectContext:backgroundThreadContext]];
[BGRequest setIncludesSubentities:NO];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"codes == %@", [product valueForKey:@"product_codes"]];
[BGRequest setPredicate:predicate];
NSError *err;
NSArray *results = [backgroundThreadContext executeFetchRequest:BGRequest error:&err];
if (results.count == 0){
// Product doesn't exist with code, make a new product
NSLog(@"Product not found for add/update (%@)", [product valueForKey:@"product_name"]);
NSManagedObject* newProduct;
newProduct = [NSEntityDescription insertNewObjectForEntityForName:@"Products" inManagedObjectContext:backgroundThreadContext];
[newProduct setValue:[product valueForKey:@"product_name"] forKey:@"name"];
[newProduct setValue:[product valueForKey:@"product_codes"] forKey:@"codes"];
if ([product valueForKey:@"information"] == (id)[NSNull null]){
// No information, NULL
[newProduct setValue:@"" forKey:@"information"];
} else {
NSString *information = [product valueForKey:@"information"];
[newProduct setValue:information forKey:@"information"];
}
} else {
NSLog(@"Product found for add/update (%@)", [product valueForKey:@"product_name"]);
// Product exists, update existing product
for (NSManagedObject *r in results) {
[r setValue:[product valueForKey:@"product_name"] forKey:@"name"];
if ([product valueForKey:@"information"] == (id)[NSNull null]){
// No information, NULL
[r setValue:@"" forKey:@"information"];
} else {
NSString *information = [product valueForKey:@"information"];
[r setValue:information forKey:@"information"];
}
}
}
// Is very important that you save the context before moving to the Main Thread,
// because we need that the new object is writted on the database before continuing
NSError *error;
if(![backgroundThreadContext save:&error])
{
NSLog(@"There was a problem saving the context (add/update). With error: %@, and user info: %@",
[error localizedDescription],
[error userInfo]);
}
// Now let's move to the main thread
dispatch_async(dispatch_get_main_queue(), ^
{
// If you have a main thread context you can use it, this time i will create a
// new one
// NSManagedObjectContext *mainThreadContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
// [mainThreadContext setPersistentStoreCoordinator:self.persistentStoreCoordinator];
self.productDBCount = self.productDBCount + 1;
float progress = ((float)self.productDBCount / (float)self.totalCount);
int percent = progress * 100.0f;
// NSNumber *progress = [NSNumber numberWithFloat:((float)self.productDBCount / (float)self.totalCount)];
self.downloadUpdateProgress.progress = progress;
self.percentageComplete.text = [NSString stringWithFormat:@"%i", percent];
NSLog(@"Added / updated product %f // ProductDBCount: %i // Percentage progress: %i // Total Count: %i", progress, self.productDBCount, percent, self.totalCount);
if (self.productDBCount == self.totalCount){
[self updatesCompleted:[jsonArray valueForKey:@"last_updated"]];
}
});
});
}
if ([deletions count] > 0){
for (id d in deletions){
dispatch_async(backgroundDispatchQueue,
^{
id deleted = d;
// Because at this point we are running in another thread we need to create a
// new NSManagedContext using the app's persistance store coordinator
NSManagedObjectContext *backgroundThreadContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
[backgroundThreadContext setPersistentStoreCoordinator:self.persistentStoreCoordinator];
NSFetchRequest *BGRequest = [[NSFetchRequest alloc] init];
// NSLog(@"Running.. (%@)", deleted);
[BGRequest setEntity:[NSEntityDescription entityForName:@"Products" inManagedObjectContext:backgroundThreadContext]];
[BGRequest setIncludesSubentities:NO];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"codes == %@", [deleted valueForKey:@"product_codes"]];
[BGRequest setPredicate:predicate];
NSError *err;
NSArray *results = [backgroundThreadContext executeFetchRequest:BGRequest error:&err];
if (results.count == 0){
// Product doesn't exist with code, make a new product
NSLog(@"Product not found, can't delete.. %@", [deleted valueForKey:@"product_name"]);
} else {
NSLog(@"Product found, deleting: %@", [deleted valueForKey:@"product_name"]);
// Product exists, update existing product
for (NSManagedObject *r in results) {
[backgroundThreadContext deleteObject:r];
}
}
// Is very important that you save the context before moving to the Main Thread,
// because we need that the new object is writted on the database before continuing
NSError *error;
if(![backgroundThreadContext save:&error])
{
NSLog(@"There was a problem saving the context (delete). With error: %@, and user info: %@",
[error localizedDescription],
[error userInfo]);
}
// Now let's move to the main thread
dispatch_async(dispatch_get_main_queue(), ^
{
self.productDBCount = self.productDBCount + 1;
float progress = ((float)self.productDBCount / (float)self.totalCount);
int percent = progress * 100.0f;
// NSNumber *progress = [NSNumber numberWithFloat:((float)self.productDBCount / (float)self.totalCount)];
self.downloadUpdateProgress.progress = progress;
self.percentageComplete.text = [NSString stringWithFormat:@"%i", percent];
NSLog(@"Deleted product %f // ProductDBCount: %i // Percentage progress: %i // Total Count: %i", progress, self.productDBCount, percent, self.totalCount);
if (self.productDBCount == self.totalCount){
[self updatesCompleted:[jsonArray valueForKey:@"last_updated"]];
}
/*
*
* Change the completion changes to a method. Check to see if the total number of products == total count. If it does, run the completion method.
*
*/
});
});
}
}
}
把 IF 放在 dispatch 里面，最后运行一个 save
// Create a new background queue for GCD
dispatch_queue_t backgroundDispatchQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0);
// id product = p;
// Dispatch the following code on our background queue
dispatch_async(backgroundDispatchQueue,
^{
NSManagedObjectContext *backgroundThreadContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
[backgroundThreadContext setPersistentStoreCoordinator:self.persistentStoreCoordinator];
for (id p in products) {
id product = p;
// Because at this point we are running in another thread we need to create a
// new NSManagedContext using the app's persistance store coordinator
NSFetchRequest *BGRequest = [[NSFetchRequest alloc] init];
NSLog(@"Running.. (%@)", product);
[BGRequest setEntity:[NSEntityDescription entityForName:@"Products" inManagedObjectContext:backgroundThreadContext]];
[BGRequest setIncludesSubentities:NO];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"codes == %@", [product valueForKey:@"product_codes"]];
[BGRequest setPredicate:predicate];
NSError *err;
NSArray *results = [backgroundThreadContext executeFetchRequest:BGRequest error:&err];
if (results.count == 0){
// Product doesn't exist with code, make a new product
NSLog(@"Product not found for add/update (%@)", [product valueForKey:@"product_name"]);
NSManagedObject* newProduct;
newProduct = [NSEntityDescription insertNewObjectForEntityForName:@"Products" inManagedObjectContext:backgroundThreadContext];
[newProduct setValue:[product valueForKey:@"product_name"] forKey:@"name"];
[newProduct setValue:[product valueForKey:@"product_codes"] forKey:@"codes"];
if ([product valueForKey:@"information"] == (id)[NSNull null]){
// No information, NULL
[newProduct setValue:@"" forKey:@"information"];
} else {
NSString *information = [product valueForKey:@"information"];
[newProduct setValue:information forKey:@"information"];
}
} else {
NSLog(@"Product found for add/update (%@)", [product valueForKey:@"product_name"]);
// Product exists, update existing product
for (NSManagedObject *r in results) {
[r setValue:[product valueForKey:@"product_name"] forKey:@"name"];
if ([product valueForKey:@"information"] == (id)[NSNull null]){
// No information, NULL
[r setValue:@"" forKey:@"information"];
} else {
NSString *information = [product valueForKey:@"information"];
[r setValue:information forKey:@"information"];
}
}
}
// Is very important that you save the context before moving to the Main Thread,
// because we need that the new object is writted on the database before continuing
// Now let's move to the main thread
dispatch_async(dispatch_get_main_queue(), ^
{
// If you have a main thread context you can use it, this time i will create a
// new one
// NSManagedObjectContext *mainThreadContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
// [mainThreadContext setPersistentStoreCoordinator:self.persistentStoreCoordinator];
self.productDBCount = self.productDBCount + 1;
float progress = ((float)self.productDBCount / (float)self.totalCount);
int percent = progress * 100.0f;
// NSNumber *progress = [NSNumber numberWithFloat:((float)self.productDBCount / (float)self.totalCount)];
self.downloadUpdateProgress.progress = progress;
self.percentageComplete.text = [NSString stringWithFormat:@"%i", percent];
NSLog(@"Added / updated product %f // ProductDBCount: %i // Percentage progress: %i // Total Count: %i", progress, self.productDBCount, percent, self.totalCount);
NSDate *currentProcessedDate = [NSDate date];
NSTimeInterval timeSinceStarted = [currentProcessedDate timeIntervalSinceDate:self.startProcessing];
NSInteger remainingProcesses = self.totalCount - self.productDBCount;
float timePerProcess = timeSinceStarted / (float)self.productDBCount;
float remainingTime = timePerProcess * (float)remainingProcesses;
self.timeRemaining.text = [NSString stringWithFormat:@"ETA: %0.0f minutes", fmodf(remainingTime, 60.0f)];
if (self.productDBCount == self.totalCount){
[self updatesCompleted:[jsonArray valueForKey:@"last_updated"]];
}
/*
*
* Change the completion changes to a method. Check to see if the total number of products == total count. If it does, run the completion method.
*
*/
});
}
NSError *error;
if(![backgroundThreadContext save:&error])
{
NSLog(@"There was a problem saving the context (add/update). With error: %@, and user info: %@",
[error localizedDescription],
[error userInfo]);
}
});