In the method below I'm receiving "EXC_BAD_ACCESS" on the line containing the "urlString" variable. My research suggests that this error occurs when the program sends a message to a variable that has already been released. However since I'm using ARC I'm not manually releasing memory. How can I prevent ARC from releasing this variable too soon?
-(NSMutableArray *)fetchImages:(NSInteger *)count {
//prepare URL request
NSString *urlString = [NSString stringWithFormat:#"http://foo.example.com/image?quantity=%#", count];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:urlString]];
//Perform request and get JSON as a NSData object
NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
//Parse the retrieved JSON to an NSArray
NSError *jsonParsingError = nil;
NSArray *imageFileData = [NSJSONSerialization JSONObjectWithData:response options:0 error:&jsonParsingError];
//Create an Array to store image names
NSMutableArray *imageFileNameArray;
//Iterate through the data
for(int i=0; i<[imageFileData count];i++)
{
[imageFileNameArray addObject:[imageFileData objectAtIndex:i]];
}
return imageFileNameArray;
}
Your problem has nothing to do with ARC. NSInteger isn't a class, so you don't want to be using the %# format. %# is going to send a description method to what the system thinks is an object, but when it turns out not to be one - CRASH. To solve your problem, you have two options:
You might want:
NSString *urlString =
[NSString stringWithFormat:#"http://foo.example.com/image?quantity=%d",
*count];
Make sure the count pointer is valid first!
You might need to change your method signature to be:
-(NSMutableArray *)fetchImages:(NSInteger)count;
and then change the urlString line as follows:
NSString *urlString =
[NSString stringWithFormat:#"http://foo.example.com/image?quantity=%d",
count];
You'll also need to fix all of the callers to match the new signature.
The second option seems more "normal" to me, but without more of your program it's impossible to be more specific.
you also may want to alloc and init the
NSMutableArray *imageFileNameArray;
before adding objects to it, otherwise you'll keep crashing. So you'd have
//Create an Array to store image names
NSMutableArray *imageFileNameArray = [[NSMutableArray alloc] init];
Related
I am parsing some XML using TouchXML and I am getting a crash -EXC_BAD_ACCESS. What I found out through trial and error was that if I don't release my CXMLDocument (which I allocate), then everything is fine. Here's my code:
- (NSArray *)getLookUps {
//Do some stuff and then...
NSData *tempData = [NSURLConnection sendSynchronousRequest:request
returningResponse:nil
error:nil];
CXMLDocument *xmlDoc = [[CXMLDocument alloc] initWithData:tempData options:0 error:nil];
NSDictionary *mappings = [NSDictionary dictionaryWithObject:#"http://****/****"
forKey:#"****"];
NSLog(#"%#", [[NSString alloc] initWithData:tempData encoding:NSUTF8StringEncoding]);
NSArray *orders = [[xmlDoc rootElement] nodesForXPath:#"//****:Unit"
namespaceMappings:mappings
error:nil];
NSMutableArray *units = [NSMutableArray arrayWithCapacity:200];
for (CXMLElement *order in orders) {
NSArray *nodes = [order children];
NSMutableDictionary *dictionary = [NSMutableDictionary dictionaryWithCapacity:[nodes count]];
for (CXMLElement *node in nodes) {
[dictionary setObject:[node stringValue] forKey:[node name]];
}
[units addObject:dictionary];
}
//[xmlDoc release];
return units;
}
See on the 2nd last line, [xmlDoc release]. I have commented that out, because it crashes if I don't. What am I doing wrong? Thanks.
You probably need to retain your dictionary object otherwise it will also be released when you release the parser. Try changing [units addObject:dictionary]; to [units addObject:[dictionary retain]];.
Another idea is to set your xmlDoc pointer to autorelease:
CXMLDocument *xmlDoc = [[[CXMLDocument alloc] initWithData:tempData options:0 error:nil] autorelease];
This bug was reported and is flagged as fixed in the newer versions of the library.
http://code.google.com/p/touchcode/issues/detail?id=35
I haven't tested to see if it is actually fixed, a comment at that URL suggests that it isn't.
In my opinion, this library should be avoided altogether. For iOS apps, use libxml2 for several reasons:
It's tested and tried, through and through
It's fast and efficient
Building a node based representation of your XML might make it easier to code with, but it wastes memory as you always have the entire document in memory. You probably have it more than once while parsing. You should instead design your code to work with the libxml2 approach. You'll agree once you start parsing documents of substantial size.
I used TouchXML quite often, and (fortunately?) I did not have this problem up to now, but it just happened ...
I posted a solution here:
Memory crash using [CXMLNode nodesForXPath] with namespace mappings
I observed in TouchXML Class "CXMLDocument" we have the following handling in "dealloc" method.
- (void)dealloc
{
// Fix for #35 http://code.google.com/p/touchcode/issues/detail?id=35 -- clear up the node objects first (inside a pool so I _know_ they're cleared) and then freeing the document
#autoreleasepool {
nodePool = NULL;
}
//
xmlUnlinkNode(_node);
xmlFreeDoc((xmlDocPtr)_node);
_node = NULL;
}
I am not sure why we are using "autoreleasepool" in "dealloc". Is this is standard coding? Correct me if I am wrong.
In the context of an iPhone app I am developing, I am parsing some html to extract data to map, using NSRegularExpression. This information is updated whenever the user "pans" the map to a new location.
This works fine the first time or two through, but on the second or third time the function is called, the application hangs. I have used XCode's profiler to confirm I am not leaking memory, and no error is generated (the application does not terminate, it just sits in execution at the point shown below).
When I examine the HTML being parsed, I do not see that it is incomplete or otherwise garbled when the application hangs.
Furthermore, if I replace the regex code with a collection of explicitly address strings, everything works as expected.
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
// receivedData contains the returned HTML
NSString *result = [[NSString alloc] initWithData:receivedData encoding:NSASCIIStringEncoding];
NSError *error = nil;
NSString *pattern = #"description.*?h4>(.*?)<\\/h4>.*?\"address>[ \\s]*(.*?)<.*?zip>.*?(\\d{5,5}), US<";
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:pattern
options:NSRegularExpressionDotMatchesLineSeparators
error:&error];
__block NSUInteger counter = 0;
// the application hangs on the next line after 1-2 times through
[regex enumerateMatchesInString:result options:0 range:NSMakeRange(0, [result length]) usingBlock:^(NSTextCheckingResult *match, NSMatchingFlags flags, BOOL *stop){
NSRange range = [match rangeAtIndex:2];
NSString *streetAddress =[result substringWithRange:range];
range = [match rangeAtIndex:3];
NSString *cityStateZip = [result substringWithRange:range];
NSString *address = [NSString stringWithFormat:#"%# %#", streetAddress, cityStateZip];
EKItemInfo *party = [self addItem:address]; // geocode address and then map it
if (++counter > 4) *stop = true;
}];
[receivedData release];
[result release];
[connection release]; //alloc'd previously, so release here.
}
I realize this is going to be difficult/impossible to duplicate, but I was wondering if anyone has run into a similar issue with NSRegularExpression or if there is something obviously wrong here.
I also have encountered the regular expression exception, too. In my case, the problem was Character Encoding. So that I wrote a code to go well with several character encoding. Maybe this code help you.
+ (NSString *)encodedStringWithContentsOfURL:(NSURL *)url
{
// Get the web page HTML
NSData *data = [NSData dataWithContentsOfURL:url];
// response
int enc_arr[] = {
NSUTF8StringEncoding, // UTF-8
NSShiftJISStringEncoding, // Shift_JIS
NSJapaneseEUCStringEncoding, // EUC-JP
NSISO2022JPStringEncoding, // JIS
NSUnicodeStringEncoding, // Unicode
NSASCIIStringEncoding // ASCII
};
NSString *data_str = nil;
int max = sizeof(enc_arr) / sizeof(enc_arr[0]);
for (int i=0; i<max; i++) {
data_str = [
[NSString alloc]
initWithData : data
encoding : enc_arr[i]
];
if (data_str!=nil) {
break;
}
}
return data_str;
}
You can download the whole category library from GitHub and just run it. I wish this helps you.
https://github.com/weed/p120801_CharacterEncodingLibrary
Maybe the answer to this question can be found at: NSRegularExpression enumerateMatchesInString: [...] usingBlock does never stop .
I had this issue solved by passing NSMatchingReportCompletion as option and by setting stop to YES when the match is nil.
I'm using TouchJson to parse json data from facebooks graph api. I'm getting some memory leaks though, and I don't really understand why...
In my effort to find the leak, I've removed everything else, so the following code is what I'm left with. The leak is one NSCFString for each loop, and I understand that it comes from the assignement to myItem.date, but I don't understand why?
I'm using the latest version of TouchJson
NSError *error;
NSDictionary *jsonDictionary = [[CJSONDeserializer deserializer] deserializeAsDictionary:data error:&error];
NSArray *jsonArray = [jsonDictionary objectForKey:#"data"];
for (NSDictionary *jsonEntry in jsonArray) {
NSDictionary *fromDictionary = [jsonEntry objectForKey:#"from"];
NSString *userId = [fromDictionary objectForKey:#"id"];
// Continue if it is a post from Atlas
if (userId != nil && [userId isEqualToString:#"10465958627"]){
MyItem *myItem = [[MyItem alloc] init];
// This uncommented causes the leak, why?
myItem.date = [jsonEntry objectForKey:#"created_time"];
[myItem release];
}
}
Thank you for your help!
Edit: I forgot to mention that MyItem is just an object with a property like so
#property (nonatomic, copy) NSString *date;
I am new to ObC and have a problem that i just cant fix. There may be other issues as well but the main issue is this:
Starting the app
Press button = load new view
In the new viewDidLoad i call another object/function and send a NSMutableArray
Process data and send back a NSMutableArray
App crash, see comment where. Most often when i go back and back again but sometimes the first time
As i am new to this i guess i do a lot of this wrong but could someone nice take a look at the code and give me some advice. I would assume i have problem with releasing something.
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(#" ");
NSLog(#"viewDidLoad ");
NSLog(#" ");
NSLog(#">>Processing prepareGame<<");
NSMutableArray *propArray1 = [[NSMutableArray alloc] initWithObjects:#"9999", nil]; //Init with dummy numbers
AccessPropertiesFile *readMyProperties = [AccessPropertiesFile new]; //Init function call to read file
NSLog(#"Prepare to call readProperties");
propArray1 = [readMyProperties readPropertiesFile:propArray1];
NSLog(#"Back from readProperties:error after this");
/*
for (NSString *element in propArray1) {
NSLog(#"Elements in prop2Array; %#", element);
}
*/
[readMyProperties release];
[propArray1 release];
}
-(NSMutableArray *)readPropertiesFile:(NSMutableArray *)readDataArray {
NSLog(#"Processing readProperties");
// For error information
NSError *error;
//Prepare File Manager
NSString *filePath = [self dataFilePath];
NSFileManager *fileMgr;
fileMgr = [NSFileManager defaultManager];
NSArray *propertiesArray = [NSArray alloc]; //Alloc array
//Check from what module the call is coming from to ecide what to do
if ([fileMgr fileExistsAtPath: filePath] == NO) {
NSLog (#"File not found");
//File does not exists, this is the first time the game starts
//Set up default parameters
NSString *fileString =#"0\n30\n30\n10\n1\n1\n1\n2\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n";
// Write default parameters to file
[fileString writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:&error];
propertiesArray = [fileString componentsSeparatedByString:#"\n"]; // each line, adjust character for line endings
}
else { //File exists
NSLog (#"File exists");
NSString *fileString = [NSString stringWithContentsOfFile:filePath
encoding:NSUTF8StringEncoding error:nil]; // reads file into memory as an NSString
propertiesArray = [fileString componentsSeparatedByString:#"\n"]; // each line, adjust character for line endings
}
//Clean readDataArray
[readDataArray removeAllObjects];
//Populate return array
for (NSString *element in propertiesArray) {
//NSLog(#"Elements in propertiesArray; %#", element);
[readDataArray addObject:element];
}
NSLog(#"readDataArray: %#", readDataArray);
[propertiesArray release];
[readDataArray autorelease];
NSLog(#"returning from readProperties");
return readDataArray;
}
#end
You are over-releasing readDataArray (known as propArray1 in the method that didn't create it). You create it and autorelease it in your second method, then you release it again at the end of your first method (where it wasn't created).
I suggest you use Analyze feature that comes with latest XCode. It is a good feature that I always use to track if I forget to release or release too much.
I also spotted that you also over-release the propertiesArray because it contains the result from [fileString componentsSeparatedByString:], which will be autorelease according to Cocoa convention.
I'm writing an iPhone native app using the JSON framework.
My app is accessing web services using JSON. The JSON data we send has nested objects, below is an example of the data served up:
{
"model": {
"JSONRESPONSE": {
"authenticationFlag": true,
"sessionId": "3C4AA754D77BFBE33E0D66EBE306B8CA",
"statusMessage": "Successful Login.",
"locId": 1,
"userName": "Joe Schmoe"
}
}
}
I'm having problem parsing using the objectForKey and valueForKey NSDictionary methods. I keep getting invalidArgumentException runtime errors.
For instance, I want to query the response data for the "authenticationFlag" element.
Thanks,
Mike
Seattle
It is hard to tell without some more details (e.g. the JSON parsing code that you are using), but two things strike me as possible:
you are not querying with a full path. In the case above, you'd need to first get the enclosing model, the json response, and only then ask the json response dictionary for the authenticationFlag value:
[[[jsonDict objectForKey:#"model"]
objectForKey:#"JSONRESPONSE"] objectForKey:#"authenticationFlag"]
perhaps you're using c-strings ("") rather than NSStrings (#"") as keys (although this would likely crash nastily or just not compile). The key should be something than can be cast to id.
While possible, both are probably false, so please include more detail.
The following is taken directly from Dan Grigsby's Tutorial at - http://mobileorchard.com/tutorial-json-over-http-on-the-iphone/ - Please attribute, stealing is bad karma.
Fetching JSON Over HTTP
We’ll use Cocoa’s NSURLConnection to issue an HTTP request and retrieve the JSON data.
Cocoa provides both synchronous and asynchronous options for making HTTP requests. Synchronous requests run from the application’s main runloop cause the app to halt while it waits for a response. Asynchronous requests use callbacks to avoid blocking and are straightforward to use. We’ll use asynchronous requests.
First thing we need to do is update our view controller’s interface to include an NSMutableData to hold the response data. We declare this in the interface (and not inside a method) because the response comes back serially in pieces that we stitch together rather than in a complete unit.
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController {
IBOutlet UILabel *label;
NSMutableData *responseData;
}
To keep things simple, we’ll kick off the HTTP request from viewDidLoad.
Replace the contents of :
#import "JSON/JSON.h"
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
responseData = [[NSMutableData data] retain];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:#"XYZ.json"]];
[[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 {
label.text = [NSString stringWithFormat:#"Connection failed: %#", [error description]];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
[connection release];
}
- (void)dealloc {
[super dealloc];
}
#end
This mostly boilerplate code initializes the responseData variable to be ready to hold the data and kicks off the connection in viewDidload; it gathers the pieces as they come in in didReceiveData; and the empty connectionDidFinishLoading stands ready to do something with the results.
Using The JSON Data
Next, we’ll flesh out the connectionDidFinishLoading method to make use of the JSON data retrieved in the last step.
Update the connectionDidFinishLoading method :
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
[connection release];
NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
[responseData release];
NSArray *luckyNumbers = [responseString JSONValue];
NSMutableString *text = [NSMutableString stringWithString:#"Lucky numbers:\n"];
for (int i = 0; i < [luckyNumbers count]; i++)
[text appendFormat:#"%#\n", [luckyNumbers objectAtIndex:i]];
label.text = text;
}
It creates an NSArray. The parser is very flexible and returns objects — including nested objects — that appropriately match JSON datatypes to Objective-C datatypes.
Better Error Handling
Thus far, we’ve been using the the convenient, high-level extensions to NSString method of parsing JSON. We’ve done so with good reason: it’s handy to simple send the JSONValue message to a string to accessed to the parsed JSON values.
Unfortunately, using this method makes helpful error handling difficult. If the JSON parser fails for any reason it simply returns a nil value. However, if you watch your console log when this happens, you’ll see messages describing precisely what caused the parser to fail.
It’d be nice to be able to pass those error details along to the user. To do so, we’ll switch to the second, object-oriented method, that the JSON SDK supports.
Update the connectionDidFinishLoading method in :
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
[connection release];
NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
[responseData release];
NSError *error;
SBJSON *json = [[SBJSON new] autorelease];
NSArray *luckyNumbers = [json objectWithString:responseString error:&error];
[responseString release];
if (luckyNumbers == nil)
label.text = [NSString stringWithFormat:#"JSON parsing failed: %#", [error localizedDescription]];
else {
NSMutableString *text = [NSMutableString stringWithString:#"Lucky numbers:\n"];
for (int i = 0; i < [luckyNumbers count]; i++)
[text appendFormat:#"%#\n", [viewcontroller objectAtIndex:i]];
label.text = text;
}
}
Using this method gives us a pointer to the error object of the underlying JSON parser that we can use for more useful error handling.
Conclusion :
The JSON SDK and Cocoa's built-in support for HTTP make adding JSON web services to iPhone apps straightforward.
NSString* aStr;
aStr = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
NSDictionary *dictionary = [aStr JSONValue];
NSArray *keys = [dictionary allKeys];
// values in foreach loop
for (NSString *key in keys) {
NSArray *items = (NSArray *) [dictionary objectForKey:key];
for (id *item in items) {
NSString* aStrs= item;
NSLog(#" test %#", aStrs);
NSDictionary *dict = aStrs;
NSArray *k = [dict allKeys];
for (id *it in k) {
NSLog(#"the child item: %#", [NSString stringWithFormat:#"Child Item -> %# value %#", (NSDictionary *) it,[dict objectForKey:it]]);
}
Now, Objective c has introduced in build class for JSON Parsing.
NSError *myError = nil;
NSDictionary *resultDictionary = [NSJSONSerialization JSONObjectWithData:self.responseData options:NSJSONReadingMutableLeaves error:&myError];
http://developer.apple.com/library/ios/#documentation/Foundation/Reference/NSJSONSerialization_Class/Reference/Reference.html
So utilize this class and make your application error free...:)