I've tried to retrieve all rows from my table by following the example at:
http://alexefish.tumblr.com/post/29843064002/fetching-every-row-of-a-table-with-parse-and-pfquery
... on iOS7 is crashes with an exc_bad_access the line weakPointer() to call the loop one more time.
Do you know a fix for that?
We were having the same issue, so I ended up rewriting the code to avoid blocks, which weren't really necessary. The code was crashing because weakPointer became nil.
This code is in an extension of PFQuery but could be adapted in different ways too.
#import "PFQuery+Additions.h"
#implementation PFQuery (Additions)
- (void)findAllObjectsInBackgroundWithBlock:(PFArrayResultBlock)block {
self.limit = 1000;
[self putObjectsWithSkip:0 into:[NSMutableArray array] block:block];
}
- (void)putObjectsWithSkip:(NSInteger)skip into:(NSMutableArray *)results block:(PFArrayResultBlock)block {
self.skip = skip;
[self findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (error) {
block(nil, error);
}
else {
[results addObjectsFromArray:objects];
if (objects.count == self.limit) {
[self putObjectsWithSkip:(skip + self.limit) into:results block:block];
}
else {
block(results, nil);
}
}
}];
}
#end
I've tested this up to 5,600 objects. The limit of skip is 10,000 (a total of 11,000 objects) so we might need to adapt again soon.
Related
I'm trying to develop and Action Extension for iOS9.1 that is supposed to query Parse for some data.
I've added, enabled and tested Parse in the extension and I'm successful at creating test objects and checking for current user.
I can not get the code inside Parse's query method
[query findObjectsInBackgroundWithBlock:^ to execute. LLDB just keeps skipping it so I'm really at a loss.
This code executes perfectly within the container app so I'm a bit confused.
- (void)viewDidLoad
{
[super viewDidLoad];
[Parse enableLocalDatastore];
[Parse enableDataSharingWithApplicationGroupIdentifier:#"group.com.app.slinky"
containingApplication:#"com.app.Slinky"];
[Parse setApplicationId:#"xxxxx"
clientKey:#"xxxxx"];
for (NSExtensionItem *item in self.extensionContext.inputItems) {
for (NSItemProvider *itemProvider in item.attachments) {
if ([itemProvider hasItemConformingToTypeIdentifier:(NSString *)kUTTypePropertyList]) {
[itemProvider loadItemForTypeIdentifier:(NSString *)kUTTypePropertyList options:nil completionHandler:^(NSDictionary *jsDict, NSError *error) {
dispatch_async(dispatch_get_main_queue(), ^{
NSDictionary *jsPreprocessingResults = jsDict[NSExtensionJavaScriptPreprocessingResultsKey];
NSString *pageTitle = jsPreprocessingResults[#"title"];
NSString *pageURL = jsPreprocessingResults[#"URL"];
if ([pageURL length] > 0) {
self.siteURL.text = pageURL;
self.URLstring = pageURL;
}
if ([pageTitle length] > 0) {
self.siteTitle.text = pageTitle;
}
});
}];
break;
}
}
}
[self queryParse];
}
-(void)queryParse{
PFQuery *query = [self.friendsRelation query];
[query orderByAscending:#"username"];
**[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (error) {
NSLog(#"%# %#", error, [error userInfo]);
} else {
self.friends = objects;
[self.tableView reloadData];
}
}];**
}
There are some limit to fetch Objects from Parse. Read Here
One has a limit of obtaining 100 objects, but anything from 1 to 1000 has a valid limit.
You have to set the limit again for the query for next objects and skip the properties of PFQuery.
You will have to query again and again until you reach the total count.
For Example - If you have 3000 objects to be fetched, then you have to query 3 times with a count of say 1000.
OR
Call [self queryParse]; inside dispatch_async(dispatch_get_main_queue(), ^{ }); block.
Hope this might workout.
This was just a result of a 12 hour refractoring marathon :-(
When I moved the queryParse call into its own method. I lost the definition of
self.friendsRelation = [[PFUser currentUser] objectForKey:#"friendsRelation"];
essentially sending a bad query... I don't know why it isn't return an error but regardless I can check that off now.
Thank you all for you help!
I need to upload some data to server. Just before doing so, I fetch an entity that this data should be bounded to(simple relationship). If there is no such entity, I want to create it then and continue uploading process. The problem, though, is that if there are too many requests, all requests will end up faster than creation of the entity, thus many entities will be created. The solution is to dispatch the block of code synchronously, but on a different thread. How do I do this?
dispatch_sync(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,0), ^{
PFQuery *query = [PFQuery queryWithClassName:#"FileOwner"];
[query whereKey:#"identifier" equalTo:#"ABCDEFG"];
PFObject *fileOwner = [query getFirstObject];
if(fileOwner){
[self continueUploadingData:data completionHandler:completionBlock];
}
else{
PFObject *newFileOwner = [PFObject objectWithClassName:#"FileOwner"];
newPhotoOwner[#"identifier"] = #"ABCDEFG";
[newPhotoOwner saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
if(succeeded)[self continueUploadingData:data completionHandler:completionBlock];
}];
}
});
This works, but obviously blocks the main thread. I can't use detachSelector: toTarget: withObject: because I have more than one argument.
The general purpose advice that will help here is to build the atomic functions with methods that take completion blocks (like parse's, maybe like your continueUploading method).
In this case, we need a function that will look for an object, return it if it's found, or create and return it if it's not found, all asynch...
- (void)findOrCreateFileOwnerWithIdentifier:(NSString *)identifier completion:(void (^)(PFObject *, NSError *))completion {
PFQuery *query = [PFQuery queryWithClassName:#"FileOwner"];
[query whereKey:#"identifier" equalTo:identifier];
[query getFirstObjectInBackgroundWithBlock:^(PFObject *object, NSError *error) {
if (object) {
return completion(object, nil);
} else {
PFObject *newFileOwner = [PFObject objectWithClassName:#"FileOwner"];
newFileOwner[#"identifier"] = identifier;
[newFileOwner saveInBackgroundWithBlock:completion];
}
}];
}
Now you can say...
[self findOrCreateFileOwnerWithIdentifier:#"ABCDEFG" completion:^(PFObject *fileOwner, NSError *error) {
if (!error) {
[self continueUploadingData:data completionHandler:completionBlock];
} else {
// handle error... probably pass it to completionBlock
// not shown because the OP code doesn't show how the block is declared
}
}];
Hi am new to using Parse and am trying to load a simple Table View Controller with data from an array retrieved using Parse PFQuery. Though I can nslog the "categories" array in view did load, by the time the code reaches numberOfRowsInSection the array seems to have been reset to nil.
Any help with this would be greatly appreciated.
Btw I did try this loading the code into an array with literals and no problem the table was displayed fine.
Heres the code:
#implementation DisplayCategoriesTVC
NSArray *categories;
- (void)viewDidLoad {
[super viewDidLoad];
// CODE TO RETRIEVE CONTENTS OF THE PARSE CATEGORIES CLASS
PFQuery *query = [PFQuery queryWithClassName:#"Categories"];
// [query whereKey:#"Sequence" > #1];
[query findObjectsInBackgroundWithBlock:^(NSArray *categories, NSError *error) {
if (!error) {
// The find succeeded.
NSLog(#"Successfully retrieved %lu categories.", (unsigned long)categories.count);
} else {
// Log details of the failure
NSLog(#"Error: %# %#", error, [error userInfo]);
}
}];
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
// Return the number of rows in the section.
return [categories count];
}
The specfic question I have is, why at the numberOfRowsInSection is the categories array showing nil value?
The specific question I have is why does the categories array now show nil and what can I do to keep the values that were loaded by the PFQuery and use them in my other methods?
You're performing something on the background thread:
findObjectsInBackground:
What does this mean since you're new?
What's the difference between synchronous and asynchronous calls in Objective-C, versus multi-threading?
So how do you reload the tableView when your data finally does aggregate from the background task?
You simply, reload the tableView, but we need to do it on the main thread because UI updates happen there:
[self.tableView reloadData];
For more info see :
iPhone - Grand Central Dispatch main thread
So completely:
PFQuery *query = [PFQuery queryWithClassName:#"Categories"];
// [query whereKey:#"Sequence" > #1];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (!error) {
// The find succeeded.
NSLog(#"Successfully retrieved %lu categories.", (unsigned long)categories.count);
self.categories = objects;
//Since this is a UI update we need to perform this on the main thread:
dispatch_async(dispatch_get_main_queue(), ^{
[self.tableView reloadData];
});
} else {
// Log details of the failure
NSLog(#"Error: %# %#", error, [error userInfo]);
}
}];
Your query has completed its task before your UI is updated because it's happening on the background thread, so you need to tell your UI components when it is done.
I am using this query to find users, it works but it just shows me the first user. I want it to show me the user with the text of an UITextField.
How can I do that ?
(I have a textfield and there I type in a name and then it should show the parsed users with the name)
PFQuery *query = [PFUser query];
NSArray *users = [query findObjects];
userQuerys.text = users[0][#"username"];
Thanks very much
This code will fetch you all the PFUsers in which username is equal to the name parameter:
- (void)searchUsersNamed:(NSString *)name withCompletion:(void (^)(NSArray *users))completionBlock {
PFQuery *query = [PFUser query];
[query whereKey:#"username" equalTo:name];
[query findObjectsInBackgroundWithBlock:^(NSArray *users, NSError *error) {
if (!error) {
// we found users with that username
// run the completion block with the users.
// making sure the completion block exists
if (completionBlock) {
completionBlock(users);
}
} else {
// log details of the failure
NSLog(#"Error: %# %#", error, [error description]);
}
}];
}
An example, if you need to update the UI with the result, for example, a table:
- (void)someMethod {
// we will grab a weak reference of self to perform
// work inside the completion block
__weak ThisViewController *weakSelf = self;
//replace ThisViewController with the correct self class
[self searchUsersNamed:#"Phillipp" withCompletion:^(NSArray *users) {
//perform non-UI related logic here.
//set the found users inside the array used by the
//tableView datasource. again, just an example.
weakSelf.users = users;
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
//pefrorm any UI updates only
//for example, update a table
[weakSelf.tableView reloadData];
}];
}];
}
A small note: the completionBlock here wont run if there is an error, but it will run even if no users were found, so you gotta treat that (if needed. in this example, it was not needed).
Avoid running non-UI related logic on that mainQueue method, you might lock the Main thread, and that`s bad user experience.
how can I ignore new fetching if one is already running. Here is one example of my code:
So if i call [self getParticipants] how to make sure to ignore if already running. The only solution I've got is to create BOOL property "inMiddleOfFetching" but I dont want to create anther BOOL property just for this. Is there a better solution?
- (void)getParticipants {
PFQuery *participantsQuery = [self.participantsRelation query];
[participantsQuery includeKey:#"client"];
[participantsQuery findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (objects)
self.participants = objects;
}];
}
This is not simpler but it is better, you can use bolts to create a single task for the query, this way if it is called multiple times it will only run once but all calls will return the value at the same time.
Something like this:
#property BFTask* task;
- (BFTask *)getParticipants {
if (!_task) {
PFQuery *participantsQuery = [self.participantsRelation query];
[participantsQuery includeKey:#"client"];
_task = [participantsQuery findObjectsInBackground];
}
return _task;
}
Then to get the result:
[[self getParticipants] continueWithBlock:^id(BFTask *task) {
if(!task.error){
self.participants = task.result;
}
_task = nil; //if you want to run the query again in the future
return nil;
}];