I'm making an application in Xcode, and running into some problems. I'm using the GameKit framework to allow for bluetooth communication between two iOS devices. The application is setup so that one of the devices is the "master" and the other is the "slave," changing it's screen content based on data received from the "master" device. The user can select whether to be the master or the slave, and when that choice is made, the other device automatically becomes the opposite role. This is all done in one view controller class. When a role is chosen, a subview is added to the baseViewController.
What my problem is, is that when the subview that is added, I would like to be able to send data using the methods in the baseViewController class. With the current setup, the device invoking the action becomeMaster:sender crashes.
What I've tried so far is,
BaseViewController:
-(IBAction)becomeMaster:(id)sender {
[self dataToSend:#"slave"]; //tells peer device to become slave, since this device is master
masterViewController = [[MasterViewController alloc] initWithNibName:#"MasterViewController" bundle:nil];
[masterViewController setBaseViewController:self];
[self.view addSubview:masterViewController.view];
}
-(void)dataToSend:(NSString *)direction {
//—-convert an NSString object to NSData—-
NSData* data;
NSString *str = [NSString stringWithString:direction];
data = [str dataUsingEncoding: NSASCIIStringEncoding];
[self mySendDataToPeers:data];
}
-(void)dataToSend:(NSString *)direction {
//—-convert an NSString object to NSData—-
NSData* data;
NSString *str = [NSString stringWithString:direction];
data = [str dataUsingEncoding: NSASCIIStringEncoding];
[self mySendDataToPeers:data];
}
//----------------------------------------------------------------------------//
- (void)receiveData:(NSData *)data fromPeer:(NSString *)peer inSession:(GKSession *)session context:(void *)context {
//—-convert the NSData to NSString—-
NSString* str;
str = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
[self useReceivedData:str];
[str release];
}
-(void)useReceivedData:(NSString *)str {
if ([str isEqualToString:#"forward"]) {
[slaveViewController.view setBackgroundColor:[UIColor blackColor]];
}
}
MasterViewController:
-(void)setBaseViewController:(BaseViewController *)bvc {
baseViewController = bvc;
}
-(IBAction)goForward:(id)sender {
actionLabel.text = #"goingForward";
[baseViewController dataToSend:#"forward"];
}
Most of that code is part of the standard Apple documentation/examples, but I included it for understanding the flow of logic.
I believe the problem originates to with the becomeMaster:sender and setBaseViewController:bvc methods. Could anyone help fix? Thanks so much!
What kind of crash are you getting? EXC_BAD_ACCESS? Try turning on NSZombieEnabled in your executable's arguments. It's difficult to say what could be causing the crash, but you might try changing your setBaseViewController: implementation to this:
-(void)setBaseViewController:(BaseViewController *)bvc {
[self willChangeValueForKey:#"baseViewController"];
[baseViewController autorelease]
baseViewController = [bvc retain];
[self didChangeValueForKey:#"baseViewController"];
}
And add [baseViewController release]; to MasterViewController's -dealloc method.
Keep in mind that it's not entirely necessary to have a custom setter for baseViewController. If you have the following property declaration in your header file:
#property (nonatomic, retain) BaseViewController *baseViewController;
And you use #synthesize baseViewController, the -setBaseViewController: method is already generated for you, with key-value observing support built in. If you aren't familiar with Objective-C 2.0 properties, I suggest reading Apple's documentation.
Related
I am trying to create a loose version of LazyTabelImages using storyboard and JSON. in ViewDidLoad on my main TableViewController, I start an NSURLConnection to get the JSON data, but my cells do not load until after the connection is completed. I want the same behavior that LazyTableImages has, where the cells load as blanks, but then have the information filled in (reload the table data). I can duplicate this if I do not use storyboard, as LazyTables does not use storyboard, but that is not an option.
I have looked through LazyTableImages to try to find the solution, but storyboard make a big difference (to me anyway).
Is there a simple way to get the cells to load as blanks? For example, if the device has no internet, I still want my TableView to show up, and I will put a custom message in the cell.
Code:
The part of my viewDidLoad where I initialize the connection....
NSURLRequest *urlrequest = [NSURLRequest requestWithURL:[NSURL URLWithString:serverURL]];
self.dataConnection = [[NSURLConnection alloc] initWithRequest:urlrequest delegate:self];
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
connectionDidFinnishLoading...
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
//ListData below is an array that my data received (JSON) is loaded into. It is then passed to getTableData.
self.dataConnection = nil;
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self performSelectorOnMainThread:#selector(getTableData:) withObject:ListData waitUntilDone:YES];
});
}
getTableData...
-(void)getTableData:(NSData *)jsonData
{
NSError *error = nil;
arrayEntries = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableLeaves error:&error];
for (int x = 0; x < arrayEntries.count; x++)
{
NSMutableDictionary *dic = [arrayEntries objectAtIndex:x];
//ARecord is a class just like in LazyTableImages that creates objects to keep the icons/data together. The ARecords are loaded into the TableView
ARecord *arecord = [[ARecord alloc] init];
NSString *title = [dic objectForKey:#"title"];
NSString *subt = [dic objectForKey:#"subtitle"];
NSString *url = [dic objectForKey:#"image_URL"];
arecord.Icon = nil;
arecord.URL = url;
arecord.Name = title;
arecord.title = subt;
//this is where I load an array full of the arecord objects.
[array addObject:arecord];
}
[self.tableView reloadData];
}
I've done something similar. In viewDidLoad: I set the array for table data to a few objects of [NSNull null] for however many blank rows I want to show while the data is downloading. In cellForRowAtIndexPath: I check if [self.arrayOfTableData objectAtIndex:indexPath.row] = [NSNull null]. If so return a "blank" cell, otherwise load the cell with ARRecrod data.
Then when the URL completes, replace the array of NSNulls with array of your ARRecords.
I do this with two objects. First, I have an image fetcher class that downloads data asynchronously and notifies a delegate when it's complete. Then I have an image view class that implements the fetcher's delegate methods. So something like:
#implementation AsyncImageFetcher
-(id)initWithURL:(NSURL *)aURL andDelegate:(id<SomeProtocol>)aDelegate{
//...
NSURLRequest *req = [NSURLRequest requestWithURL:aURL];
//Note that NSURLConnection retains its delegate until the connection
//terminates! See comments in MyImageView below.
[NSURLConnection connectionWithRequest:req delegate:self];
//...
}
//Implement standard connection delegates here. The important part is:
-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
// ...
UIImage *anImage = [self decodeDownloadedDataIntoAnImage];
if([[self delegate] respondsToSelector:#selector(imageFetcher:didFetchImage:)]){
[[self delegate] imageFetcher:self didFetchImage:anImage];
}
//...
}
#end
Then I subclass UIImageView or UIView or something (depending on how flexible you need to be) to implement the delegate protocol and fire off the fetcher:
#implementation MyImageView
-(id)initWithURL:(NSURL *)aURL andPlaceHolderImage:(UIImage *)aPlaceHolder{
//...
[self setImage:aPlaceHolder];
//Note we don't assign this to an ivar or retain it or anything.
//That's ok because the NSURLConnection inside the fetcher actually
//retains the fetcher itself. So it will live until the connection
//terminates -- which is exactly what we want. Thus we disable
//CLANG's noisy warnings.
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-value"
[[AsyncImageFetcher alloc] initWithURL:aURL andDelegate:self];
#pragma clang diagnostic pop
return self;
}
-(void)imageFetcher:(MCMAsyncImageFetcher *)anImageFetcher didFetchImage:(UIImage *)anImage{
[self setImage:anImage];
}
#end
In your specific case, you'd just set a MyImageView as your cell's imageView in -tableView:cellForRowAtIndexPath:, passing reasonable values for its placeholder and URL, of course.
Since I haven't see your code, I just give my suggestion here:
- (void)viewDidLoad
{
[super viewDidLoad];
dispatch_queue_t queue = dispatch_queue_create(NULL, NULL);
dispatch_async(queue, ^{
//add your connection code here
//parse the json and store the data
//
dispatch_async(dispatch_get_main_queue(), ^{
//here to reload your table view again,
//since UI related method should run on main thread.
[YOUR_TABLEVIEW reloadData];
});
});
[YOUR_TABLEVIEW reloadData];
}
Note: Make sure your tableview in storyboard has connected to that in code! Hope it helps!
I get leaks if I dont put it in dealloc. I get a crash EXC_BAD_ACCESS If I do. I cannot see anything wrong with this code. The bad access is pointed at [events release]. Have I made a mistake in the code below or is Instruments just having a laugh at my expense?
events is an NSArray
#interface EventsViewController : UITableViewController
{
#private
NSArray *events;
}
- (void)viewDidLoad
{
events = [[self getEvents] retain];
}
- (void)dealloc
{
[events release];
[super dealloc];
}
- (NSArray*)getEvents
{
NSMutableArray *response = [[[NSMutableArray alloc] init] autorelease];
//Some sql
while(sqlite3_step(statement) == SQLITE_ROW)
{
Event *event = [[[Event alloc] init] autorelease];
event.subject = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 0)];
[response addObject:event];
}
return response;
}
Update
A lot of you are saying the code is fine which is a plus. I dont manipulate events elsewhere - I have removed any code that does to try and single out the crash. Perhaps its in the parent view?
This is the click event that pushes the EventsViewController:
- (void)eventsClick:(id)sender
{
EventsViewController *eventsViewController = [[EventsViewController alloc] initWithNibName:#"EventsViewController" bundle:nil];
eventsViewController.anywhereConnection = anywhereConnection;
eventsViewController.contact = contact;
[[self navigationController] pushViewController:eventsViewController animated:YES];
[eventsViewController release];
}
The crash is actually happening when I return to the parent view. (I think it is considered a parent in this scenario). But perhaps the [eventsViewController release] just triggers dealloc in the EventViewController.
Have you considered just refactoring your code to use ARC? It works with iOS 4 and up and will make your life a lot easier. There are plenty of tutorials out there that will guide you how to do it, and will remove the need to manually figure out the nuances of memory management.
If your Events object has property 'subject' set as assign, then the results of stringWithUTF8String: will not be retained. (Same thing if Events is a C++ object.)
The stringWithUTF8String: method returns an auto-released object that will be released at the next turn of the event loop.
There is a huge difference when you reference a variable via "self", and when you don't.
When you use
events = [[self getEvents] retain];
the memory allocated in getEvents never gets stored in the class property and is basically a leak.
You need to use
self.events = [self getEvents]; // no need to use retain if property is correctly defined.
Then
[events release];
should work fine.
try putting
events = nil;
in dealloc.
I'm in the process of trying to move code from a UITableViewController class to a "helper" class.
The code utilizes NSURLConnection to grab and parse JSON and then populate an NSMutableArray.
What I'd like to do is call a method in my helper class that returns a NSMutableArray. What I don't understand is how to return the array from the connectionDidFinishLoading delegate class of NSURLConnection (where the array is actually built) as though it was from the originally called method that started the connection. In other words, how does the method that calls NSURLConnection get control back so it can return a value from the whole operation?
Here are the relevant methods from the helper class. How do I get the getMovies method to return the listOfMovies that is built in the connectionDidFinishLoading delegate class?
-(NSMutableArray)getMovies:(NSURL*)url {
responseData = [[NSMutableData data] retain];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
//NSURLRequest* request = [NSURLRequest requestWithURL: url cachePolicy: NSURLRequestUseProtocolCachePolicy timeoutInterval: 30.0];
connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
[responseData setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
[responseData appendData:data];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
//TODO error handling for connection
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
//---initialize the array---
listOfMovies = [[NSMutableArray alloc] init];
tmdbMovies = [[NSArray alloc] init];
posters = [[NSArray alloc] init];
thumbs = [[NSDictionary alloc] init];
NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
SBJsonParser *json = [[SBJsonParser new] autorelease];
tmdbMovies = [json objectWithString:responseString];
// loop through all the top level elements in JSON
for (id movie in tmdbMovies) {
// 0 - Name
// 1 - Meta
// 2 - Url
if ((NSNull *)[movie objectForKey:#"name"] != [NSNull null]) {
if (![[movie objectForKey:#"name"] isEqualToString:#""]) {
name = [movie objectForKey:#"name"];
}
}
if ((NSNull *)[movie objectForKey:#"info"] != [NSNull null]) {
if (![[movie objectForKey:#"info"] isEqualToString:#""]) {
meta = [movie objectForKey:#"info"];
}
}
if ((NSNull *)[movie objectForKey:#"thumb"] != [NSNull null]) {
if (![[movie objectForKey:#"thumb"] isEqualToString:#""]) {
thumbUrl = [movie objectForKey:#"thumb"];
}
}
NSLog(#"Name: %#", name);
NSLog(#"Info: %#", meta);
NSLog(#"Thumb: %#", thumbUrl);
NSMutableArray *movieData = [[NSMutableArray alloc] initWithObjects:name,meta,thumbUrl,nil];
// add movieData array to listOfJMovies array
[listOfMovies addObject:movieData];
[movieData release];
}
//FIXME: Connection warning
if (connection!=nil) {
[connection release];
}
[responseData release];
[responseString release];
}
What you really need to do here is create a #protocol that creates a delegate for your helper class. Then change -(NSMutableArray)getMovies:(NSURL*)url to -(void)getMovies:(NSURL*)url
The class that is calling your helper method needs to implement your helper method's delegate.
Then - (void)connectionDidFinishLoading:(NSURLConnection *)connection calls the delegate method(s). It's best to have a one for success and one for failure.
=Update Begin=
You will need to also define an id delegate in your helper file which the calling class sets to self after init but before calling -(void)getMovies:(NSURL*)url. That way the helper file knows where to call back to.
getMovies *movieListCall = [[getMovies alloc] init];
movieListCall.delegate = self;
[movieListCall getMovies:<your NSURL goes here>];
You will see some additional lines for the inclusion of a delegate in both the getMovies.h and getMovies.m files.
=Update End=
in your getMovies.h file add:
#protocol getMoviesDelegate
#required
- (void)getMoviesSucceeded:(NSMutableArray *)movieArray;
- (void)getMoviesFailed:(NSString *)failedMessage;
#end
#interface getMovies : NSOBject {
id delegate;
}
#property (nonatomic, assign) id delegate;
in your getMovies.m file add:
#synthesize delegate;
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
//TODO error handling for connection
if ([delegate respondsToSelector:#selector(getMoviesFailed:)]) {
[delegate getMoviesFailed:[error localizedDescription]];
}
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
//finishes with
if ([delegate respondsToSelector:#selector(getMoviesSucceeded:)]) {
[delegate getMoviesSucceeded:listOfMovies];
}
}
update your calling class .h file to use getMoviesDelegate:
#interface MoviesView : UIViewController <getMoviesDelegate>{
.
.
.
}
add the getMoviesDelegate methods to your calling class .m file
- (void)getMoviesSucceeded:(NSMutableArray *)movieArray {
//deal with movieArray here
}
- (void)getMoviesFailed:(NSString *)failedMessage {
//deal with failure here
}
This is not tested but hopefully gives you a road map to work with.
Protocols are nice because you can make both required and optional delegate methods and it helps in refining your helper methods to become very reusable across projects. The compiler will also warn you if you have implemented a protocol but not implemented the protocol's required delegate methods. If you follow this path be sure to use conformsToProtocol: and respondsToSelector:
Fundamentally, what's happening is that you're starting an asynchronous network load (asynchronous is the right way to do this, almost assuredly), and then you need some way to resume whatever operation you were doing before the load began. You have a few options:
Create your own delegate protocol. Your UITableViewController would then set itself as the helper's delegate, and the helper would call helperDidLoad or whatever you named that method. There's more information on writing delegates in the Cocoa Programming Guide.
Use blocks and continuation passing style. This is a bit more advanced but I like it. In your UITableViewController you'd write something like this:
[helper doSomething:^ (id loaded) {
[modelObject refresh:loaded]; // or whatever you need to do
}];
And then in your helper you'd write:
- (void)doSomething:(void ^ (id))continuation {
_continuation = continuation;
//kick off network load
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
_continuation(_data);
}
Use notifications. Read the NSNotificationCenter docs.
Use KVO. The KVO programming guide has a lot of good info on Key-Value Observing.
How to i get the getMovies method to return the listOfMovies that is built in the connectionDidFinishLoading delegate class?
I'm going to argue that you should not do that.
Network requests should be made asynchronously. If your getMovies were to make a synchronous request and return only when it had data you would block that entire thread while you waiting for a network connection to finish. This is a bad idea in general and a terrible idea if your main thread is calling getMovies. Blocking the main thread will prevent you from responding to touches or updating the UI, your app will appear frozen, and the OS will terminate it if your users don't quit in frustration first.
Instead have the helper class notify the caller when data is available (or when it failed to retrieve data) through a delegate call back, notification, KVO, or whatever mechanism you prefer.
Here are the steps, pseudocode like style:
[helperInstance setDelegate:self]; // where self is your UITableViewController class
in your helper class, in the connectionDidFinishLoading do something like this:
[delegate finishedLoadingData:JSONData];
Also you can define a protocol for your delegate, and the declare the delegate like this in your helper class:
#property (nonatomic, assign) id<YourProtocol> delegate;
Hope this helps,
Moszi
I Have a small problem with NSCoding and NSKeyedArchiver when persisting my App Settings class and was hoping someone could spot an issue if it's my code, I am relatively new to Obj-C but have plenty of coding experience in numerous languages so the code seems ok to me but...
I have an instance class to hold my app Settings, the class itself is a retained property of the main App Delegate, this is created via a
#interface AppDelegate : NSObject <UIApplicationDelegate> {
Settings *settings;
[...]
}
#property (nonatomic, retain) Settings *settings;
[...]
This is created in the applicationDidFinishLaunching event as:
settings = [Settings LoadSettings];
If I comment out the above line then the app works fine every time, however if I pull the oject back from persisted settings using NSCoder and NSKeyedUnarchiver, the SIGARBT error is thrown as a NSCFString selector is being sent for what is encoded as a boolean property? The Settings Class is defined as an NSObject which implements the protocol.
#interface Settings : NSObject <NSCoding>
As I say, creating an instance of the settings class is fine, there is no issue, saving it seems OK as well as checking the returning class from the LoadSettings method shows the right values, only after exiting the method does the expected bool value seem to be getting sent to the load method as an NSCFString
- (id)initWithCoder:(NSCoder *)decoder {
if (self = [super init]) {
[...]
self.animateMenus = [decoder decodeBoolForKey:#"animateMenus"];
}
return self;
}
- (void)encodeWithCoder:(NSCoder *)encoder {
[...]
[encoder encodeBool:animateMenus forKey:#"animateMenus"];
}
Once the settings have been loaded the property in question is used like this:
SettingsViewController *settingsView = [[SettingsViewController alloc] initWithNibName:#"SettingsView" bundle:nil];
[self presentModalViewController:settingsView animated:[AppDelegate instance].settings.animateMenus];
[settingsView release];
**The animateMenus member of the settings class will now throw the following:
-[NSCFString animateMenus]: unrecognized selector sent to instance 0xc712570 2010-10-15 11:12:51.828 App[900:207] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSCFString animateMenus]: unrecognized selector sent to instance 0xc712570'
Whereas, taking the 'settings = [Settings LoadSettings];' call out of the app start-up removes the issue (but then always uses the app defaults)?
Load and Save Methods:
+ (Settings*) LoadSettings {
Settings *s = nil;
#try {
NSData *data = [[NSUserDefaults standardUserDefaults] objectForKey:#"settings"];
if (data == nil) {
s = [[Settings alloc] init];
[s Initialise];
[s SaveSettings];
}
else
s = (Settings*)[NSKeyedUnarchiver unarchiveObjectWithData:data];
}
#catch (NSException * e) {
NSLog(#"Error Loading Settings\n%#", [e reason]);
}
#finally {
return s;
}
}
// Saves the settings dictionary to the user's device documents folder..
- (void) SaveSettings {
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:self];
[[NSUserDefaults standardUserDefaults] setObject:data forKey:#"settings"];
}
Load is a static method all other members of Settings are instance.
You need to do:
settings = [[Settings LoadSettings] retain];
That's because in your LoadSettings, the result of NSKeyedUnarchiver is an autoreleased object. And it got released :-) At that location a new object was created, an NSString in this case.
Edit:
Well, I just noticed a major problem with LoadSettings that I missed at first: you mix memory release strategies: in one codepath you return the result of [[Settings alloc] init] which is not autoreleased, while in the other you retain the result of NSKeyedArchiver which is autoreleased. You need to make sure only one concept is used.
Since the method name LoadSettings does not contain alloc, copy or new in its name the convention is that it should return an autoreleased object. Thus, you should do:
if (data == nil) {
s = [[Settings alloc] init];
[s Initialise];
[s SaveSettings];
[s autorelease];
}
else
...
Hey folks - I'm writing a pretty simple iPhone application. The data comes from a plist file (NSDictionary basically), that I'm trying to load into a singleton class and use across my various view controllers to access the data.
Here's the implementation for my singleton (heavily modeled after this thread)
#implementation SearchData
#synthesize searchDict;
#synthesize searchArray;
- (id)init {
if (self = [super init]) {
NSString *path = [[NSBundle mainBundle] bundlePath];
NSString *finalPath = [path stringByAppendingPathComponent:#"searches.plist"];
searchDict = [NSDictionary dictionaryWithContentsOfFile:finalPath];
searchArray = [searchDict allKeys];
}
return self;
}
- (void)dealloc {
[searchDict release];
[searchArray release];
[super dealloc];
}
static SearchData *sharedSingleton = NULL;
+ (SearchData *)sharedSearchData {
#synchronized(self) {
if (sharedSingleton == NULL)
sharedSingleton = [[self alloc] init];
}
return(sharedSingleton);
}
#end
So whenever I try to access the searchDict or searchArray properties elsewhere in my application (like a TableView delegate) like so:
[[[SearchData sharedSearchData] searchArray] objectAtIndex:indexPath.row]
I get an exception stating *** -[NSCFSet objectAtIndex:]: unrecognized selector sent to instance 0x5551f0
I'm not really sure why the objectAtIndex message is being sent to an NSCFSet object, I feel like my singleton is implemented wrong or something. I also tried a more complex singleton implementation like the one recommended by apple in the aforementioned thread and had the same problem. Thanks for any insight you can provide.
In your -init method you are directly accessing your instance variables and you are not retaining them. They're getting deallocated and their memory is being used up by other objects later on in your application's lifetime.
Either retain your objects that you're creating there or use the non-convenience methods to generate them.
searchDict = [[NSDictionary alloc] initWithContentsOfFile:finalPath];
searchArray = [[searchDict allKeys] retain];
Whenever you assign synthesized variables, do it through 'self', so:
- (id)init {
if (self = [super init]) {
NSString *path = [[NSBundle mainBundle] bundlePath];
NSString *finalPath = [path stringByAppendingPathComponent:#"searches.plist"];
self.searchDict = [NSDictionary dictionaryWithContentsOfFile:finalPath];
self.searchArray = [searchDict allKeys];
}
return self;
}
Also make sure you've set up those variables to be 'retain'ed in the header file.
Hi, Can you tell me what is the advantage, when we assign synthesized variables through 'self'? Thank you shiva
the values are set through the setter; it releases the previous value and retains the one you assign.