I have an NSArray called "malls" that contains a large number of NSDictionaries (each a specific mall) that I uploaded to Parse.com. I want my users to be able to access this information to create map annotations.
I've tried to do this in 2 different ways:
I tried uploading the entire array as a property of a single object:
this is the upload:
in the dataBank.h file:
#property (strong, nonatomic) NSMutableArray* malls;
in the .m file
PFObject *obj = [PFObject objectWithClassName:#"malls"];
obj[#"mallsData"] = self.malls;
[obj saveInBackground];
I try to get the data from parse:
-(NSMutableArray *)createAnnotationsFromParse
{
__block NSMutableArray* data = [[NSMutableArray alloc]init];
__block NSMutableArray* annots = [[NSMutableArray alloc]init];
PFQuery* query = [PFQuery queryWithClassName:#"malls"];
[query getObjectInBackgroundWithId:#"Eaib9yfTRe" block:^(PFObject *object, NSError *error) {
data = [object objectForKey:#"mallsData"];
annots = [self createAnnotations:data];
}];
return annots;
}
The problem is getObjectInBackground is asynchronous and always returns before getting the data from the server. I tried moving the "return annots" inside the code block but that gives the following error: "incompatible block pointer types".
I uploaded 5 "mall" objects to class "malls2". Each object has 2 properties- name and address:
for(int i = 0; i < 5; i++)
{
PFObject *mallsObj = [PFObject objectWithClassName:#"malls2"];
mallsObj[name] = [[self.malls objectAtIndex:i]objectForKey:name];
mallsObj[address] = [[self.malls objectAtIndex:i]objectForKey:address];
[mallsObj saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
if(succeeded)
NSLog(#"yay");
else
NSLog(#"%#", error.description);
}];
}
then I try to get it back:
-(NSMutableArray *)createAnnotationsFromParse
{
__block Annotation* anno = [[Annotation alloc]init];
__block NSMutableArray* annots = [[NSMutableArray alloc]init];
PFQuery* query = [PFQuery queryWithClassName:#"malls2"];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if(error)
NSLog(#"%#", error.description);
else
{
for(int i = 0; i < [objects count]; i++)
{
//createAnnotationWithTitle is a func in a different class that creates the annotation
anno = [anno createAnnotationWithTitle:[[objects objectAtIndex:i] objectForKey:name] andAddress:[[objects objectAtIndex:i]objectForKey:address]];
}
[annots addObject:anno];
}
}];
return annots;
}
I get 5 objects but they're all empty.
It's a basic misunderstanding about asynchronous methods with block parameters. The trick is to get out of the habit of thinking that code that appears later in a source file runs later. The assumption works in this function:
- (void)regularFunction {
// these NSLogs run top to bottom
NSLog(#"first");
NSLog(#"second");
NSLog(#"third");
}
This will generate logs: first, second, third. Top to bottom, but not in this one:
- (void)functionThatMakesAsynchCall {
// these NSLogs do not run top to bottom
NSLog(#"first");
[someObject doSomeAsynchThing:^{
NSLog(#"second");
}];
NSLog(#"third");
}
That function will generate logs - first, third, second. The "second" NSLog will run well after the "third" one.
So what should you do? Don't try to update the UI with results of a parse call until after it completes, like this:
// declared void because we can't return anything useful
- (void)doSomeParseThing {
// if you change the UI here, change it to say: "we're busy calling parse"
PFQuery* query = [PFQuery queryWithClassName:#"malls2"];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if(!error) {
// change the UI here, say by setting the datasource to a UITableView
// equal to the objects block parameter
}
}];
// don't bother changing the UI here
// don't bother returning anything here
// we just started the request
}
But what if doSomeParseThing is really a model function, whose only job is to fetch from parse, not to know anything about UI? That's a very reasonable idea. To solve it, you need to build your model method the way parse built their's, with block parameter:
// in MyModel.m
// declared void because we can't return anything useful
+ (void)doSomeParseThing:(void (^)(NSArray *, NSError *))block {
PFQuery* query = [PFQuery queryWithClassName:#"malls2"];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
block(objects, error);
}];
}
Now your view controller can call, leave the query work to your model and the UI work to the vc:
// change UI to 'busy' here
[MyModel doSomeParseThing:^(NSArray *objects, NSError *error) {
// update UI with objects or error here
}];
Figured it out. It looked like I was getting "empty objects" (can be seen here postimg.org/image/ot7ehn29b ) but once I tried to access data from the objects I saw there was no problem. Basiclly I was tricked by the PFObjects in the array showing "0 objects" and assumed it meant they came back from Parse.com empty. Here's how I checked, just for reference:
PFQuery *query = [PFQuery queryWithClassName:#"malls2"];
NSArray *array = [query findObjects];
NSLog(#"%#", [[array objectAtIndex:0] objectForKey:#"name"]; // I have a string property called "name" in my Parse object.
Related
I have a PFQuery that gets the current participants of a particular event:
PFQuery *getcurrentparticipants = [PFQuery queryWithClassName:#"Event"];
[getcurrentparticipants selectKeys:#[#"Participants"]];
[getcurrentparticipants whereKey:#"objectId" equalTo:ObjectID];
[getcurrentparticipants findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (!error) {
NSMutableArray *newParticipantsArray = [[NSMutableArray alloc]init];
if([objects[0] valueForKey:#"Participants"] == nil){ // If object retrieved in objects is null. If there are 0 participants
[newParticipantsArray addObject:PFUser.currentUser.username];
PFQuery *query = [PFQuery queryWithClassName:#"Event"];
[query getObjectInBackgroundWithId:self.ObjectID
block:^(PFObject *Event, NSError *error) {
Event[#"Participants"] = newParticipantsArray;
[Event incrementKey:#"Vacants" byAmount:[NSNumber numberWithInt:-1]];
[Event saveInBackground];
}];
}else{ // STEP 5
for(int i=0;i<objects.count;i++) {
[newParticipantsArray addObject:[[objects objectAtIndex:i] valueForKey:#"Participants"]];
}
[newParticipantsArray addObject:PFUser.currentUser.username];
NSLog(#"Part to upload %#", newParticipantsArray);
PFQuery *query = [PFQuery queryWithClassName:#"Event"];
[query getObjectInBackgroundWithId:self.ObjectID
block:^(PFObject *Event, NSError *error) {
Event[#"Participants"] = newParticipantsArray;
[Event incrementKey:#"Vacants" byAmount:[NSNumber numberWithInt:-1]];
[Event saveInBackground];
}];
}
} else {
// Log details of the failure
NSLog(#"Error: %# %#", error, [error userInfo]);
}
}];
This is how the method works:
Create a PFQuery object
Query the Participants Class for an specific ObjectId
If no error, then we create a NSMutable array
If no participants are in Parse then we insert the current user as participant.
Else, insert all participants in the mutable array and add currentuser at the end of the array.
Then upload it again to Parse
My problem is in step 5:
When I perform the tasks in the else, the column in Parse looks like this :
[["Participant 1"],"Participant 2"]
But I would like to have it like this:
["Participant 1","Participant 2"]
What I have tried:
I tried things like putting the arrays like this. [newParticipantsArray addObject:[[objects objectAtIndex:i] valueForKey:#"Participants"]]; and similar combinations, of course without luck.
It’s hard to say for sure since I can’t see the structure of your data but are you sure the value held in
[[objects objectAtIndex:i] valueForKey: #“Participants”]
Is a single user and not itself an array of users? The plural key “participants” seems to suggest it’s an array of users which would also explain the result you’re getting.
If in fact the value returned for the "Participants" key is an array, you can add the objects in it to your mutable array by doing the following:
NSArray* participants = [[objects objectAtIndex:i] valueForKey:#"Participants"]
[newParticipantsArray addObjectsInArray:participants];
This uses the addObjectsInArray: method of NSMutableArray to add the objects from the old array into the new one.
I am currently using parse to develop an iPhone app and I got this code:
I have a Class called "Event" and has a field called "EventName"
PFQuery *query = [PFQuery queryWithClassName:#"Event"];
[query selectKeys:#[#"EventName"]];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (!error) {
// The find succeeded.
NSLog(#"Successfully retrieved %lu scores.", (unsigned long)objects.count);
// Do something with the found objects
for (PFObject *object in objects) {
NSLog(#"%#", object.objectId);
}
}
}];
This works perfectly, but i get the object's IDs instead of the event names which is what i want.
EDIT :
So far I got this inside the IF statement
self.eventArray = [objects valueForKey:#"EventName"];
for(int i=0; i<10 ; i++){
NSLog(#"%#", eventArray[i]);
}
by doing that the question got solved.
All you have to do is use the objects array that was retuned from finding the objects and pass them into your array by using valueForKey.
So it would be
if (!error) {
self.yourEventNameArray = [objects valueForKey:#"EventName"];
}
I am making an app that registers users and allows them to add friends etc. So I have a LoginViewController where I retrieve the array of user's friends' objectIds when the login is successful. This function is called.
- (void) getFriendList
{
NSString * objectID = [PFUser currentUser].objectId;
NSLog(#"%#", objectID);
PFQuery *query = [PFUser query];
[query getObjectInBackgroundWithId:objectID block:^(PFObject *username, NSError *error) {
sharedClass.sharedInstance->retrievedFriends = username[#"friendsIds"];
friendListLoaded = YES;
[self getFriendsUsernames];
}];
Here i get an array object that contains object ids of all the friends this user has. As you can see when getFriendList is completed, it calls another function called GetFriendsUsernames. This function is supposed to retrieve profile pictures and usernames of those friends so I can populate the Friend List view later.
-(void) getFriendsUsernames
{
NSMutableArray * objectIDs = [[NSMutableArray alloc] initWithArray: sharedClass.sharedInstance->retrievedFriends];
PFQuery *query = [PFUser query];
int friendsCount = [objectIDs count];
for(int i = 0; i<=friendsCount;i++)
{
[query getObjectInBackgroundWithId:objectIDs[i] block:^(PFObject *username, NSError *error) {
[sharedClass.sharedInstance->friendsUsernames addObject:username[#"username"]];
[sharedClass.sharedInstance->friendsProfilePictures addObject:username[#"ProfilePicture"]];
}];
NSLog(#"%#", sharedClass.sharedInstance->friendsUsernames );
}
}
But this seems to be unsuccessful because nothing is logged on the console where it should log username of retrieved friend whenever one query gets finished. Am I doing this the right way? My array count is right so loop runs to the number of friends a user has. It also prints the username of first object in objectIds array if i put the logging command in the loop.
Your NSLog runs immediately after your query objects are queued for execution. Therefore, even if the code is running correctly (and I suspect it might not be), you'll never get the correct results you're after logged to the console.
If you have your Parse classes designed in a certain way, you could collapse this into 1 query by using the include method on PFQuery. This assumes that you've created an array of Pointers on your User object, named "friends". If you actually store the objectId (i.e., the string value) of each friend, this code won't work.
I'm not using Swift yet, so here's how I'd write this query in Objective-C:
- (void)getFriendList {
PFUser *currentUser = [PFUser currentUser];
PFQuery *query = [PFUser query];
[query whereKey:#"objectId" equalTo:currentUser.objectId];
[query includeKey:#"friends.username"];
[query includeKey:#"friends.ProfilePicture"];
[query getFirstObjectInBackgroundWithBlock:^(PFObject *user, NSError *error) {
if (error != nil) {
// Process the error
} else }
// You've got your user and the data you wanted
}
}];
}
Found it. Not the prettiest way out there but well it does what i want. gets me arrays of usernames and profile pictures of every objectID contained in array of friends.
NSMutableArray * objectIDs = [[NSMutableArray alloc] initWithArray: sharedClass.sharedInstance->retrievedFriends];
PFQuery *query = [PFUser query];
PFFile * imageFile;
//UIImage *profilePictureData;
int friendsCount = [objectIDs count];
for(int i = 0; i<friendsCount;i++)
{
PFObject * username = [query getObjectWithId:objectIDs[i]];
[sharedClass.sharedInstance->friendsUsernames addObject:username[#"username"]];
[sharedClass.sharedInstance->friendsEmailAdresses addObject:username[#"email"]];
//NSLog(#"%#",username[#"ProfilePicture"]);
imageFile = [username objectForKey:#"ProfilePicture"];
NSData *imageData = [imageFile getData];
UIImage *imageFromData = [UIImage imageWithData:imageData];
[sharedClass.sharedInstance->friendsProfilePictures addObject:imageFromData];
NSLog(#"%#", sharedClass.sharedInstance->friendsUsernames );
}
I want to set ImageView hidden or not according to the boolean value true x false, which is located in Parse database. Could you give me some ideas how to do that? Got problems because of having property ImageView in my CustomCell.h
EDIT:
PFObject *yes = [PFObject objectWithClassName:#"MyClass"];
cell.discounts.hidden = [yes[#"yesnocolumn"] boolValue];
I just don`t understand to usage of PFObject, myclass returning (null) value.
EDIT2:
PFQuery *query = [PFQuery queryWithClassName:#"Classname"];
[query whereKey:#"yesnocolumn" equalTo:#1];
[query findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {
if (!error) {
cell.discounts.hidden = YES;
}else{
cell.discounts.hidden = NO;
}}];
The boolean from the service will look like either #0 or #1, so you can't just test for truthiness, because:
if (#0) {
// this condition is true. that's surprising!
}
So the safe way to test is to say:
cell.imageView.hidden = [myParseObject[#"hidden"] boolValue];
EDIT - Now I understand the misunderstanding. Here's how parse works:
1) Create an object locally:
PFObject *yes = [PFObject objectWithClassName:#"MyClass"];
This object won't have any values initialized. So any bools it contains will be 0, or NO.
2) Set some value locally:
yes[#"yesnocolumn"] = #1; // makes it true
// or = [NSNumber numberWithBool:YES];
3) Save it. (you can also use the data browser to initialize objects manually).
[yes saveInBackground];
4) Get an object. I think this is the part that's giving you trouble... just creating a local object doesn't really do much. The idea of parse is that objects are stored in the cloud. To get them, you need a PFQuery.
PFQuery *query = [PFQuery queryWithClassName:#"MyClass"];
[query findObjectsInBackgroundWithBlock:^(NSArray *results, NSError *error) {
// this will return all (up to 100 by default, MyClass objects that are
// saved in the cloud
if (!error && results.count) {
NSLog(#"the first object is %#", results[0]);
NSLog(#"the bool is %d", [results[0][#"yesnocolumn"] boolValue];
}
}];
Does this make sense? You can't expect the object to have any values initialized until you either set them locally, or retrieve already initialized remote copies. Also note, if you run the query on the next source line after saveInBackground, you won't get the saved result, since the save won't have finished. Start out saving in one run of your app, then reviewing in the data browser, then do a query.
It's worth doing a thorough review of their docs here.
Im very new to iOS and PFQuery and I need your help please
IM trying to store the array of objects obtained form PFQuery into a local NSArray, Im trying to do it inside if (!error) but it does not leave the block, once the block terminates so does the values for it on my array.
//InstallersDirectory.m
#interface InstallersDirectoryTVC ()
#property (nonatomic, strong) NSArray *supervisors;
#end
//more code goes here
- (void)viewDidLoad
{
[super viewDidLoad];
PFQuery *query = [PFQuery queryWithClassName:#"InstallersInfo"];
[query whereKey:#"supervisor" equalTo:#"yes"];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (!error) {
for (PFObject *object in objects) {
self.supervisors = [objects valueForKey:#"supervisor"];
}
}else {
NSLog(#"Error, %# %#",error,[error userInfo]);
}
}];
Everything works inside the block, like self.supervisors.count or NSLog, but it doesn't leave the block at all. Could you please tell me how I can get those values store definitely to self.supervisors?
Thanks !!
edit | comment
If you still need help on this issue, here is a suggestion or two:
first, self.supervisors is a NSArray. As a NSArray it has to be fully initialized and populated at creation time. So, even though you are iterating through your results, you are creating a new array each time which means only the last iteration would likely be stored in self.supervisors.
try this instead,
#property (nonatomic,strong) NSMutableArray *supervisors;
in your block:
[self.supervisors addObject:object];
//note: this will put the entire returned object in your mutable array
then later outside your block:
to list all the supervisors:
for (PFObject *supervisor in self.supervisors) {
NSLog(#"supervisor info:%#",supervisor);
}
To get the 4th supervisor in the list:
PFObject *superVisorNumber4 = [self.supervisors objectAtIndex:4];
To get the phone number from that supervisor (making this up :)
NSString *phone = [superVisorNumber4 objectForKey:#"phone"];
hope that helps