I am relatively new to GCD, I am currently using it to create a singleton object in my application. After doing some research I found using GCD's dispatch_once() method is the best way to achieve the singleton design pattern. For some reason, my code is breaking and I can not figure it out for the life of me. Below, I have pasted my singleton creation/init code, and the responding error.
+(id)sharedErrorMapper {
static dispatch_once_t onceToken;
static id sharedInstance;
dispatch_once(&onceToken, ^
{
sharedInstance = [[self alloc] init];
});
return sharedInstance;
}
-(id)init {
//creating the ErrorMap data structure
//currently loading in dummy JSON data..
self = [super init];
if (self != nil) {
NSError *error = [[NSError alloc] init];
NSData *resourceData = [[NSData alloc] initWithContentsOfFile:
#"/Users/acuram/Desktop/GitHubWorkspaces/ios-sdk-src/ios-here-sdk/PPHSDKTests/Resources"];
self.errorMap = [[NSDictionary alloc] init];
self.errorMap = [NSJSONSerialization JSONObjectWithData:resourceData options:kNilOptions error:&error];
}
return self;
}
After setting some breakpoints and doing some stack tracing, my code is breaking at the dispatch_once() function call. The error I get back is a "NSInvalidArgumentException", it complains that my data parameter is nil. I am pretty shocked because I followed a legit tutorial video on youtube to implement this, I am also looking at my companies code base and they seem to do it in a similar way....
Related
In the iOS7 SDK and while using MRC, the following piece of code does not return the shared instance. On runtime it just hangs and it does not move in to the next line of code.
+(id)getInstance
{
static dispatch_once_t pred;
static IAPManager *inAppManager = nil;
dispatch_once(&pred, ^{
inAppManager = [[IAPManager alloc] init];
});
return inAppManager;
}
What is the reason for this anomaly? This is how I am calling
IAPManager *iapManager = [IAPManager getInstance];
if ([iapManager canMakePurchases]) {
[iapManager loadStore:proUpgradeProductId];
}else{
UIAlertView *aView = [[UIAlertView alloc]initWithTitle:#"" message:#"This device is not able or allowed to make payments" delegate:nil cancelButtonTitle:#"Ok" otherButtonTitles: nil];
[aView show];
}
The original getInstance method is absolutely fine (I would declare it as returning IAPManager*, but it doesn't make any difference to how it works). "static" variables are initialised once wherever they are.
The problem is most likely that getInstance is called from [[IAPManager alloc] init]. Calling dispatch_once from inside the dispatch_once is an instant deadlock. To find out, you just set a breakpoint in getInstance on the dispatch_once statement. It should be hit once during the first call, and then probably again, and the original call will be on the stack. Or just wait until it hangs, then check in the debugger where each thread is. You'll find a thread waiting for dispatch_once to finish.
Alternatively, it is possible that the init method just doesn't return. Maybe it does some network access that doesn't finish. To step into the code, set a breakpoint on the first (and only) line of the block, that is the [[IAPManager alloc] init] line. Once that breakpoint is reached, you can step through the code.
Diclare inAppManager object outside the method. and use the following code
static IAPManager *inAppManager = nil;
+(id)getInstance
{
if (nil != inAppManager) {
return inAppManager;
}
static dispatch_once_t pred;
dispatch_once(&pred, ^{
inAppManager = [[IAPManager alloc] init];
});
return inAppManager;
}
That may help you.
Thanks
Satya
Try this:
+(instancetype)getInstance
{
static id inAppManager;
static dispatch_once_t pred;
dispatch_once(&pred, ^{
inAppManager = [[[self class] alloc] init];
});
return inAppManager;
}
I've got 2 classes, MPRequest and MPModel.
The MPModel class has a method to lookup something from the core data store, and if not found, creates an MPRequest to retrieve it via a standard HTTP request (The method in MPModel is static and not and instance method).
What I want is to be able to get a progress of the current HTTP request. I know how to do this, but I'm getting a little stuck on how to inform the view controller. I tried creating a protocol, defining a delegate property in the MPRequest class, altering the method in MPModel to accept this delegate, and in turn passing it to the MPRequest when it is created.
This is fine, however ARC is then releasing this delegate whilst the request is running and thus doesn't do what I want. I'm trying to avoid making my delegate object a strong reference in case it throws up any reference cycles but I don't know any other way of doing this.
To start the request, from my view controller I'm running
[MPModel findAllWithBlock:^(NSFetchedResultsController *controller, NSError *error) {
....
} sortedBy:#"name" ascending:YES delegate:self]
Inside the findAllWithBlock method, I have
MPRequest *objRequest = [MPRequest requestWithURL:url];
objRequest.delegate = delegate;
[objRequest setRequestMethod:#"GET"];
[MPUser signRequest:objRequest];
[objRequest submit:^(MPResponse *resp, NSError *err) {
...
}
And in the MPRequest class I have the following property defined :
#property (nonatomic, weak) NSObject<MPRequestDelegate> *delegate;
Any ideas or suggestions?
As requested, here is some more code on how things are being called :
In the view controller :
[MPPlace findAllWithBlock:^(NSFetchedResultsController *controller, NSError *error) {
_placesController = controller;
[_listView reloadData];
[self addAnnotationsToMap];
[_loadingView stopAnimating];
if (_placesController.fetchedObjects.count > 0) {
// We've got our places, but if they're local copies
// only, new ones may have been added so just update
// our copy
MPSyncEngine *engine = [[MPSyncEngine alloc] initWithClass:[MPPlace class]];
engine.delegate = self;
[engine isReadyToSync:YES];
[[MPSyncManager sharedSyncManager] registerSyncEngine:engine];
[[MPSyncManager sharedSyncManager] sync];
}
} sortedBy:#"name" ascending:YES delegate:self];
Here, self is never going to be released for obvious reasons, so I don't see how this is the problem.
Above, MPPlace is a subclass of MPModel, but the implementation of the findAllWithBlock:sortedBy:ascending:delegate: is entirely in MPModel
The method within MPModel looks like this
NSManagedObjectContext *context = [[MPCoreDataManager sharedInstance] managedObjectContext];
[context performBlockAndWait:^{
__block NSError *error;
NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:NSStringFromClass([self class])];
[request setSortDescriptors:#[[[NSSortDescriptor alloc] initWithKey:key ascending:asc]]];
NSFetchedResultsController *controller = [[NSFetchedResultsController alloc] initWithFetchRequest:request
managedObjectContext:context
sectionNameKeyPath:nil
cacheName:nil];
[controller performFetch:&error];
if (!controller.fetchedObjects || controller.fetchedObjects.count == 0) {
// Nothing found or an error, query the server instead
NSString *url = [NSString stringWithFormat:#"%#%#", kMP_BASE_API_URL, [self baseURL]];
MPRequest *objRequest = [MPRequest requestWithURL:url];
objRequest.delegate = delegate;
[objRequest setRequestMethod:#"GET"];
[MPUser signRequest:objRequest];
[objRequest submit:^(MPResponse *resp, NSError *err) {
if (err) {
block(nil, err);
} else {
NSArray *objects = [self createListWithResponse:resp];
objects = [MPModel saveAllLocally:objects forEntityName:NSStringFromClass([self class])];
[controller performFetch:&error];
block(controller, nil);
}
}];
} else {
// Great, we found something :)
block (controller, nil);
}
}];
The delegate is simply being passed on to the MPRequest object being created. My initial concern was that the MPRequest object being created was being released by ARC (which I guess it probably is) but it didn't fix anything when I changed it. I can't make it an iVar as the method is static.
The submit method of the request looks like this :
_completionBlock = block;
_responseData = [[NSMutableData alloc] init];
[self prepareRequest];
[self prepareRequestHeaders];
_connection = [[NSURLConnection alloc] initWithRequest:_urlRequest
delegate:self];
And when the app starts downloading data, it calls :
[_responseData appendData:data];
[_delegate requestDidReceive:(float)data.length ofTotal:_contentLength];
Where _contentLength is simply a long storing the expected size of the response.
Got it working. It was partly an issue with threading, where the core data thread was ending before my request, me looking at the output from a different request entirely, and the way ARC handles memory in blocks.
Thanks for the help guys
The following are methods that I am using to retrieve data from a server while displaying a UIActivityIndicator. I'm trying to put these methods in the app delegate and then call them from other classes, but I don't know how to return my JSONData. Can anybody help with this?
-(void)startProcess:(NSString *)buildURL{
UIActivityIndicatorView *aInd = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActionSheetStyleBlackTranslucent];
[aInd setFrame:CGRectMake(0, 0, 50, 50)];
[aInd startAnimating];
// then call the timeCOnsumingmethod in separate thread.
[NSThread detachNewThreadSelector:#selector(getData:) toTarget:self withObject:buildURL];
}
- (void)getData:(NSString *)buildURL{
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
// Query our database for a restaurant's menus
NSURL *url = [NSURL URLWithString:buildURL];
NSError *e;
NSString *jsonreturn = [[NSString alloc] initWithContentsOfURL:url encoding:NSUTF8StringEncoding error:&e];
NSData *jsonData = [jsonreturn dataUsingEncoding:NSUTF32BigEndianStringEncoding];
// NSError *error = nil;
[self performSelectorOnMainThread:#selector(endProcess:) withObject:jsonData waitUntilDone:YES];
[pool release];
//return jsonData;
}
- (IBAction)endProcess:(NSData *)jsonData{
// ??????????
return jsonData;
}
Not sure why got downvoted but your approach is all wrong. Here's what you want to do:
Add the UIActivityIndicatorView
Use NSURLConnection to asynchronously retrieve the data
Use NSJSONSerialization to decode the received JSON into a NSDictionary or NSArray
Remove the UIActivityIndicatorView
Your best bet would be to implement this as a separate class that takes a delegate object. You could implement a delegate protocol to indicate states like 'started network activity' (which your delegate could use to add a spinner view), and 'received data' (which would pass the decoded object back to the delegate - the delegate could then remove the spinner).
One of the benefits of this approach is you can easily set it up so that the connection/request is canceled when the object deallocs. Then you just store the request object as a property on your delegate, and when your delegate goes away, it deallocs the request, which cancels/cleans up properly.
So here is a partial sample of the relevant code.
static NSMutableArray *radioInputArray;
static NSMutableArray *buttonsArray;
- (IBAction)lookForRadioButtons:(id)sender {
// NSLog(#"Testing");
NSError *error;
NSString *radiostr = [NSString stringWithContentsOfFile:[[NSBundle mainBundle] pathForResource:#"getRadios" ofType:#"txt"] encoding:NSASCIIStringEncoding error: &error] ;
if (radiostr == nil)
{
NSLog (#"Error! %#", error);
}
else
{
NSLog(#"%#",radiostr);
NSString *radiotxt= [webView stringByEvaluatingJavaScriptFromString:radiostr];
NSLog(#"%#", radiotxt);
NSArray *myRadios = [radiotxt componentsSeparatedByString:#"::"];
[radioInputArray addObjectsFromArray:myRadios];
NSLog(#"%d", myRadios.count);
NSLog(#"Number of buttons in global radio array %d", radioInputArray.count);
NSLog(#"%d", scrollViewer.subviews.count);
}
}
So it throws no exceptions and seems to work properly except after addObjectsFromArray:, my count in the global NSMutableArray is 0 (the count in the myRadios = 56). I am pretty sure they should be equal at this point but are not. I have declared my NSMutableArray up near the top so that it can be globally accessed. Am I missing something such as allocating and initializing this? Does it not do that automatically like in C#? Again, this is my first foray into the Objective-C world from Windows programming so please be gentle yet feel free to be critical.
Your two global arrays are not initialized.
The lines
static NSMutableArray *radioInputArray;
static NSMutableArray *buttonsArray;
just define the two variables as pointers to NSMutableArray, so you need to get them to point at an actual instance of the class NSMutableArray.
Somewhere in your initialization code, or through an accessor (best if a class method), you should set the variables to an empty, newly allocated NSMutableArray.
Here is a way to do it:
+ (NSMutableArray*)radioInputArray
{
if (!radioInputArray) {
radioInputArray = [[NSMutableArray alloc] init];
}
return radioInputArray;
}
Then use the accessor in your code instead of the global variable.
It may happen if your radioInputArray is nil,
you didn't initialize the array
you need to add
[[radioInputArray alloc] init];
before you do anything with radioInputArray
Good place for initialising object is "init" method in Global class
Ex.
-(id)init
{
if (self=[super init]) {
self.globalAllArtworkArray=[[NSMutableArray alloc] init];
self.globalCollectionArray=[[NSMutableArray alloc] init];
self.globalLookbookArray=[[NSMutableArray alloc] init];
}
return self;
}
+(ASNGlobalClass *)shareManager
{
static ASNGlobalClass *sharedInstance = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
sharedInstance = [[self alloc] init];
});
return sharedInstance;
}
I am just grasping the concepts of TDD and mocking, and am running into an issue in terms of how to properly. I have a sheet that drops down and lets a user create a new core data object and save it to the data store. I am not sure if I am taking the best approach to testing it.
- (IBAction)add:(id)sender
{
NSString *itemName = [self.itemNameTextField stringValue];
SGItem *newItem = [NSEntityDescription insertNewObjectForEntityForName:kItemEntityName inManagedObjectContext:[self managedObjectContext]];
newItem.name = itemName;
NSError *error = nil;
BOOL canSaveNewItem = [[self managedObjectContext] save:&error];
if (!canSaveNewItem)
{
[NSApp presentError:error];
}
[self clearFormFields]; // Private method that clears text fields, disables buttons
[NSApp endSheet:[self window] returnCode:NSOKButton];
}
I'm trying to write two test methods to test this: one that tests the scenario where the managed object can't save and one where it successfully saves.
#interface SGAddItemWindowControllerTests : SGTestCase
{
#private
SGAddItemWindowController *addItemWindowController;
id mockApp;
id mockNameField;
}
- (void)setUp
{
mockNameField = [OCMockObject mockForClass:[NSTextField class]];
mockApp = [OCMockObject mockForClass:[NSApplication class]];
addItemWindowController = [[BLAddItemWindowController alloc] init];
[addItemWindowController setValue:mockNameField forKey:#"itemNameTextField"];
}
- (void)testAddingNewItemFromSheetFailed
{
// Setup
NSString *fakeName = #"";
[[[mockNameField expect] andReturn:fakeName] stringValue];
[[mockApp expect] presentError:[OCMArg any]];
// Execute
[addItemWindowController add:nil];
// Verify
[mockApp verify];
}
- (void)testAddingNewItemFromSheetSucceeds
{
// Setup
NSString *fakeName = #"Item Name";
[[[mockNameField expect] andReturn:fakeName] stringValue];
[[mockApp expect] endSheet:[OCMArg any] returnCode:NSOKButton];
// Execute
[addItemWindowController add:nil];
// Verify
[mockApp verify];
[mockNameField verify];
}
#end
Here are the issues I know I have, but am not sure how to work out:
I am not sure how to handle dealing with the managed object context in terms of the test. Should I bring up the entire core data stack or just create a mock of NSManagedObjectContext?
The idea of just setting the text field values as the way to trigger the if statement seems wrong. Ideally I think I should stub out the save: method and return YES or NO, but given question 1 I'm not sure about the Core Data aspects of it all.
I think I'm on the right track, but I could use a second opinion on how to tackle my issues and set me on the right path for testing the code snippet.
Justin,
What I do for question #1 is to create an actual NSManagedObjectContext but create an im-memory persistence store. Nothing hits the disk and I test the CoreData version of the truth.
I have a MWCoreDataTest class (extends in my case GTMTestCase) that builds the moc and initializes the persistence store
- (NSManagedObjectContext *) managedObjectContext {
if (managedObjectContext != nil) {
return managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
managedObjectContext = [[NSManagedObjectContext alloc] init];
[managedObjectContext setPersistentStoreCoordinator: coordinator];
}
return managedObjectContext;
}
- (NSPersistentStoreCoordinator*)persistentStoreCoordinator;
{
if (persistentStoreCoordinator) return persistentStoreCoordinator;
NSError* error = nil;
NSManagedObjectModel *mom = [self managedObjectModel];
persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc]
initWithManagedObjectModel:mom];
if (![persistentStoreCoordinator addPersistentStoreWithType:NSInMemoryStoreType
configuration:nil
URL:nil
options:nil
error:&error]) {
[[NSApplication sharedApplication] presentError:error];
return nil;
}
return persistentStoreCoordinator;
}
WRT #2, I think that's ok - if you plan on testing more than one behavior in the class, move the
[addItemWindowController setValue:mockNameField forKey:#"itemNameTextField"];
to the testAdding.. method
If you solve #1, then you could just set the itemNameText field to nil and your save validation would trigger.
WRT #3, I would validate that building a mock on NSApp === building a mock on NSApplication
What is that you want to test? Do you want to test that Core Data does the saving or not? Or, do you want to test that your application responds correctly to the result of the call to CoreData?
Either way I think you should extract a method that performs the saving along the lines of:
-(BOOL)saveNewItem:(NSString *)itemName error:(NSError **)error {
SGItem *newItem = [NSEntityDescription insertNewObjectForEntityForName:kItemEntityName inManagedObjectContext:[self managedObjectContext]];
newItem.name = itemName;
NSError *error = nil;
return[[self managedObjectContext] save:&error];
}
- (IBAction)add:(id)sender {
NSString *itemName = [self.itemNameTextField stringValue];
NSError *error = nil;
BOOL canSaveNewItem = [self saveNewItem:itemName error:&error];
if (!canSaveNewItem) {
[NSApp presentError:error];
}
[self clearFormFields]; // Private method that clears text fields, disables buttons
[NSApp endSheet:[self window] returnCode:NSOKButton];
}
This way you can test that Core Data saving works as expected by settings up an in memory store and not have to care about the business logic. You should also be able to override or mock the result of this method for testing the business logic.
I would perhaps even move all the Core Data stuff to a separate class that would encapsulate the interaction for easier mocking.