So I have a WebView inside a custom NSObject subclass called GoogleLinkFetcher and what I do is load a request from the webview and in webView:didFinishLoadForFrame: I call self to call a method on it. If I don't call that method everything works fine, if I do an EXC_BAD_ACCESS error points to that line. I read something about EXC_BAD_ACCESS regarding deallocating and memory allocations but I'm in an ARC environment so I would expect not to have problems with that... Here is the code:
-(void)searchLinks
{
NSLog(#"searching links at googlelinksearcher url: %#", googleUrl);
NSURLRequest *request = [NSURLRequest requestWithURL:googleUrl];
[[webView mainFrame] loadRequest:request];
[webView setFrameLoadDelegate:self];
}
-(void)webView:(WebView *)sender didFinishLoadForFrame:(WebFrame *)frame
{
if(frame == sender.mainFrame)
{
NSLog(#"main frame");
[self getLinks];
}
}
The error points right to [self getLinks].
I hope somebody could help, thanks in advance!
The problem might be that you start the loading process but don't hold a strong reference to your GoogleLinkFetcher instance and it is released before the web view finishes loading (actually right after it starts).
Put a breakpoint in webView:didFinishLoadForFrame: method and check if self is still a valid instance of GoogleLinkFetcher. Or NSLog self before you call getLinks.
REVISED...
The crux of the app is communicating with a database server. Responses from the server to the app are all in XML. There are several screens. Example, screen 1 lists the user's information, screen 2 lists the user's past trades, allows new trades, and so on.
Here is some code from my AppDelegate:
StartViewController *svc = [[StartViewController alloc] init];
TradeViewController *tvc = [[TradeViewController alloc] init];
CashViewController *cvc = [[CashViewController alloc] init];
ComViewController *covc = [[ComViewController alloc] init];
PrefsViewController *pvc = [[PrefsViewController alloc] init];
NSMutableArray *tabBarViewControllers = [[NSMutableArray alloc] initWithCapacity:5];
UITabBarController *tabBarController = [[UITabBarController alloc] init];
UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:svc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:tvc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:cvc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:covc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:pvc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
[tabBarController setViewControllers:tabBarViewControllers];
[[self window] setRootViewController:tabBarController];
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
Trying to stick with the MVC style, I have a singleton class which does all of the "processing".
Now an example on how I run into a wall… the user can change their email address on screen 5. Enter new email address into text field and click the save button. The button then calls a method from the singleton class which sends the new email address to the server and (via the URL) and receives a XML response confirming the change.
Here are my problems:
1. I start the spinner from the view controller before I make the singleton class method call - but not knowing when the app to server send/receive is finished, how do I make the spinner stop at the right time? I can't of it from the singleton class, I tried that. From what I know, it has to be from within the VC or is there a way to change VC output from my singleton class?
The singleton class NSURLConnection is handling ALL of my communication. Everything from a simple, email change all the way to updating transaction tables. This just seems wrong to me and makes it very difficult to keep track on who is calling what. Again, I am going by my interpretation of MVC. I think it would be much easier to have a NSURLConnection for every VC and do some processing in those classes. However that would not be MVC(ish).
I have close to a 100 variables, arrays, etc… in my singleton class which I use to assign values to all my VC. This also seems wrong to me but I can't think of any other way.
how can I distinguish in the NSURLConnection delegate
(connectionDidFinishLoading) which URL call is being made?
Each of the delegate methods (such as -connectionDidFinishLoading:) has a connection parameter that tells you which connection sent the message. A given connection can only load one URL at a time, so there's a one to one correspondence between URLs and connections.
How can I tell outside of "connectionDidFinishLoading" when the download is completed?
That method tells you when the connection is finished. It's up to you to store that information somewhere where it's useful to your app.
Update: Based on what you've added, your "processing" class is your app's model. The rest of the app shouldn't care that each transaction involves a message to the server -- that's the model's business alone. Also, there's no reason that the model has to be a single object (let alone a singleton) -- it can be a group of objects that work together.
So, you might have a class (let's call it Processor) that represents the application's interface to the model (some might even call this a "model controller"). An instance of Processor might create a local database for storing the current local state of the app.You might also have a Transaction class that represents a single transaction with the server. A transaction could create a request, send it to the server, get the response, update the database, and tell the Processor that the transaction is done. Or, maybe when some other part of the app (like one of your view controllers) asks the Processor to process a new transaction, the Processor passes the requesting object along to the transaction that it creates so that the transaction can update the requestor directly.
It's hard to say what the best plan for your app is without knowing where you're planning on taking it, but the usual guidelines hold:
break your problem into parts that are easier to solve
limit the scope of each class's responsibilities
if something seems to complicated, it probably is
Breaking your model up into several classes will make it easier to test, as well. You can imagine how easy it would be to write a set of unit tests for the Transaction class. The same goes for Processor -- if the server transaction stuff is in a different class, it's easier to test that the Processor is doing the right thing.
If you have multiple NSURLConnections for the same delegate, consider using a global (well, let's say rather an instance variable) NSMutableDictionary instance, in which you store the data depending on which NSURLConnection is being called. You can use, for example, the in-memory address of the connections converted to an NSString (something like
[NSString stringWithFormat:#"%p", connection]
should do the trick).
Also, in the connectionDidFinishLoading: and connection:didFailLoadWithError: methods, remove the keys corresponding to the NSURLConnections. Thus, you can tell it from 'outside' if a connection is finished: just check if it is in the dictionary or not.
If you're downloading any data over a network connection, I would suggest using ASIHttpRequest. This will allow you to download files asynchronously, meaning your interface doesn't freeze during the download process.
If you use ASIHttpRequest, you can also set the didFinishSelector. By doing this, you can control which method is called when a specific URL has finished loading.
Have a look at this:
NSURL *url = [NSURL URLWithString:#"http://allseeing-i.com"];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setDelegate:self];
[request startAsynchronous];
[request setDidFinishSelector:#selector(requestDone:)];
Then:
- (void)requestDone:(ASIHTTPRequest *)request
{
// Use when fetching text data
NSString *responseString = [request responseString];
// Use when fetching binary data
NSData *responseData = [request responseData];
// If you want, you can get the url of the request like this
NSURL *url = [request url];
}
As for the second part of your question, if the requestDone: method has not been called, you know the download has not completed.
If you want to do something more complicated with multiple downloads, ASIHttpRequest offers queue functionality too. Take a look here.
Hope this will help you.
- (void)connectionDidFinishLoading:(NSURLConnection*)connection
{
NSString *urlString = [[[connection originalRequest] URL] absoluteString];
if ([urlString caseInsensitiveCompare:#"http://www.apple.com"] == NSOrderedSame) {
//Do Task#1
}
else if ([urlString caseInsensitiveCompare:#"http://www.google.com"] == NSOrderedSame)
{
//Do Task#2
}
}
I would recommend subclassing NSURLConnection. Simply add two properties: an NSInteger, tag, and a BOOL, isFinished. This way, you can #define tags for each different request and then identify them by tag in your delegate methods. In connectionDidFinishLoading, you can set the isFinished BOOL to YES, and then you can check in other methods if then connection is finished.
Here's my own NSURLConnection subclass, TTURLConnection:
TTURLConnection.h:
#import <Foundation/Foundation.h>
#interface TTURLConnection : NSURLConnection <NSURLConnectionDelegate>
#property (nonatomic) NSInteger tag;
#property (nonatomic) BOOL isLocked;
- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate startImmediately:
(BOOL)startImmediately tag:(NSInteger)tagParam;
#end
TTURLConnection.m:
#import "TTURLConnection.h"
#implementation TTURLConnection
#synthesize tag;
- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate startImmediately:
(BOOL)startImmediately tag:(NSInteger)tagParam {
self = [super initWithRequest:request delegate:delegate
startImmediately:startImmediately];
if(self) {
self.tag = tagParam;
}
return self;
}
#end
I'm trying to add a QLPreviewController's view as a subview (no--I cannot use a nav controller or modal). It only shows the fabric background of the QLPreviewController.
I create one and add it as a subview:
QLPreviewController* preview = [[[QLPreviewController alloc] init] autorelease];
preview.dataSource = self;
preview.delegate = self;
preview.view.frame = CGRectMake(0, 0, self.pdfPreviewView.frame.size.width, self.pdfPreviewView.frame.size.height);
self.pdfPreviewView.previewController = preview;
[self.pdfPreviewView addSubview:preview.view];
[preview reloadData];
My QLPreviewControllerDataSource methods work fine (viewing 1 pdf at a time):
- (id <QLPreviewItem>) previewController: (QLPreviewController *) controller previewItemAtIndex: (NSInteger) index
{
NSString *path = [[ResourceManager defaultManager] pathForPDF:self.currentPDF];
NSURL *url = [NSURL fileURLWithPath:path];
if ([QLPreviewController canPreviewItem:url]) {
return url; // This always returns
}
return nil; // This line is never executed
}
- (NSInteger)numberOfPreviewItemsInPreviewController:(QLPreviewController *)controller
{
return 1;
}
The data source method always returns the file url, and QLPreviewController says it can open the file, but it never actually does. I just get the background. The self.currentPDF is set before I create the QLPreviewController and does contain the correct information (from CoreData).
The delegate methods never get called. But I'm also not using it in a standard way, so that's not totally unexpected.
I've also tried calling [preview setNeedsLayout], [preview setNeedsDisplay'], and [preview refreshCurrentPreviewItem] but those just call the data source methods and don't change anything.
The PDFs are valid. I can open them in both Xcode and Preview, so that's not the problem. I'm kind of stumped as to why this won't work. Any help would be appreciated in getting this to work.
Turns out I was sending QLPreviewController the wrong path. It wasn't finding the PDF in the bundle correctly. I needed to use pathForResource:ofType:inDirectory.
This is my first app, and actually isn't even fully mine but rather involves re-working an existing app to add functionality.
It involves a JSON feed which I'm successfully reading in and then trying to pass the value of a URL to a view. Here's the code from my app delegate that is successfully fired once the feed is read in:
- (void)JSONFetch:(MYJSONFetch *)fetch gotTheCollection:(id)collection
{
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
self.testViewController.feedURL = [NSURL URLWithString:[collection objectForKey:#"Listings"]];
[JSONFetch release];
JSONFetch = nil;
}
Then in my testViewController I have this viewDidLoad method:
- (void)viewDidLoad {
[super viewDidLoad];
if(self.feedURL)
{
[self startDownload];
}
}
Eventhough, when I debug, the gotTheCollection method passes a value to the feedURL of the view, it then fails on the if(self feedURL) check within the view and thus the view never gets populated.
As I'm so new to this code I've no idea if the sequence is wrong, or maybe it's how I'm passing the variable.
I know the description is relatively vague but even on a basic level I don't know if this functionality works in objective C, it doesn't cause any errors though, just sits there not loading because it can't get the data.
UPDATE: Definition of FeedURL follows, in the H file:
NSURL *feedURL;
then
#property (nonatomic, retain) NSURL *feedURL;
then in the M file:
#synthesize feedURL;
Thanks for the help guys, I finally decided to just restart the entire upgrade as the project had become a mess of reworked code and I couldn't be sure what worked and what didn't. As a result there's no clear answer to this but I imagine Franks was probably the closest so I'll mark that as the answer.
The NSURL is being autoreleased, you will need to retain it yourself
Assign the NSURL to feedURL, like so
self.testViewController.feedURL = [[NSURL URLWithString:[collection objectForKey:#"Listings"]] retain];
This will also mean you will have to release it yourself.
I have a view controller that lists some data in an UITableView. To get the data downloaded I use ASIHTTPRequest which methods I have put in another class.
In my view controller I have setup the appropriate delegates to handle the data that is being retrieved from ASIHTTPRequest. So from my view controller in - viewDidLoad I alloc and init my class that holds the ASIHTTPRequest methods like so:
self.officesParser = [[[OfficesParser alloc] init] autorelease]; // retained property
Then in - viewDidAppear: I call [officesParser downloadOffices];
My - downloadOffices method looks like this:
- (void)downloadOffices {
// 1. Downloaded offices.json
NSURL *officesUrl = [NSURL URLWithString:#"http://example.com/example.json"];
ASIHTTPRequest *officesRequest = [ASIHTTPRequest requestWithURL:officesUrl];
// Always ask the server if there is new content available,
// If the request fails, use data from the cache even if it should have expired.
[officesRequest setCachePolicy:ASIAskServerIfModifiedCachePolicy|ASIFallbackToCacheIfLoadFailsCachePolicy];
// Store the cache permanently
[officesRequest setCacheStoragePolicy:ASICachePermanentlyCacheStoragePolicy];
[officesRequest setTag:1];
OfficesViewController *vc = [[OfficesViewController alloc] init];
[officesRequest setDelegate:vc];
[vc release];
[officesRequest startAsynchronous];
}
Everytime after calling the [officesParser downloadOffices] method I get:
*** -[OfficesViewController respondsToSelector:]: message sent to deallocated instance 0x6a2f6c0
What am I doing wrong here?
You want vc to be delegate for officesRequest, however, after you allocate and initialize vc and set it to be the delegate, you immediately release it. Please note that delegate properties are usually assign, not retain. You are then responsible for keeping your delegate object in existence until no longer needed. So, if you plan to send messages to it in a near future, you can't immediately release it.