Please someone tell me why retaining NSMutabledictionary after some operations is ok, but retain on creation gives a leak.
-(void) Func2
{
NSString *_errorDesc;
NSPropertyListFormat format;
NSString *_plistPath = [[NSBundle mainBundle] pathForResource:#"List" ofType:#"plist"];
NSData *_plistData = [[NSFileManager defaultManager] contentsAtPath:_plistPath];
NSDictionary *dataDict = (NSDictionary *) [NSPropertyListSerialization
propertyListFromData:_plistData
mutabilityOption:NSPropertyListMutableContainersAndLeaves
format:&format
errorDescription:&_errorDesc];
for (int i = 0; i<[dataDict count]; i++)
{
[_ups setObject:[NSArray arrayWithObjects:[NSNumber numberWithInt:0],[NSNumber numberWithInt:0], nil]forKey:[NSString stringWithFormat:#"%d",i]];
}
NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:_ups forKey:#"Ups"];
[defaults synchronize];
}
-(void) Func1
{
_ups = [NSMutableDictionary dictionary];
//_ups = [[NSMutableDictionary dictionary]retain]; = leak
//_ups = [[NSMutableDictionary alloc]init]; = leak
if(![[NSUserDefaults standardUserDefaults] objectForKey:#"Ups"])
{
[self Func2];
}else{
_ups = [[NSUserDefaults standardUserDefaults] objectForKey:#"Ups"];
}
[_ups retain]; // - ok
}
Instruments->Leaks shows that leak detected only when I trying to retain on creation, but if I retain after filling a dictionary all fine.
Thanks.
Looking at just one of the if paths (the second) reduces to this:
_ups = [[NSMutableDictionary alloc]init];
// Returns a retained instance assigned to _ups.
_ups = [[NSUserDefaults standardUserDefaults] objectForKey:#"Ups"];
// Now a new instance is assigned to "_ups` without releasing the first instance.
[_ups retain];
//The above retain is incorrect since the method name does not start with "new" or have "copy" in it. This implies that the returned value should be autoreleased. Review Objective-C naming conventions. See Apple's Objective-C Conventions.
All in all, best practice is to use ARC. With ARC the first instance would have been automatically released.
Related
Hello i have this function, that gets dummy data from file in project:
Issues are shown in those lines:
NSString *path = [[NSBundle mainBundle] pathForResource: #"StatisticsDataJSON" ofType: #"TXT"]; - potential leak of an object.
NSMutableDictionary *statisticsResponse = [jsonParser objectWithString:data]; - potential leak of an object stored into 'jsonParser'
for (id key in statisticsResponse) { - potential leak of an object stored into 'statisticArray'
for (int i = 0; i < statsForDate.count; i++) { - potential leak of an object stored into 's'
if (self.statistics==nil)
{
self.statistics = [[NSMutableDictionary alloc]init];
NSString *path = [[NSBundle mainBundle] pathForResource: #"StatisticsDataJSON" ofType: #"TXT"];
NSError *error = nil;
NSString *data = [NSString stringWithContentsOfFile: path
encoding: NSUTF8StringEncoding
error: &error];
//NSLog(#"%#",data);
SBJsonParser *jsonParser = [[SBJsonParser alloc] init];
NSMutableDictionary *statisticsResponse = [jsonParser objectWithString:data];
for (id key in statisticsResponse) {
NSArray *statsForDate = [statisticsResponse objectForKey:key];
NSMutableArray *statisticArray = [[NSMutableArray alloc]init];
for (int i = 0; i < statsForDate.count; i++) {
Statistic *s = [[Statistic alloc]init];
s.locationId = [[statsForDate objectAtIndex:i] objectForKey:#"locationId"];
int value =[[[statsForDate objectAtIndex:i] objectForKey:#"visits"] integerValue];
s.visits = value;
value =[[[statsForDate objectAtIndex:i] objectForKey:#"totalUsers"] integerValue];
s.totalUsers = value;
value= [[[statsForDate objectAtIndex:i] objectForKey:#"uploads"] integerValue];
s.uploads = value;
value = [[[statsForDate objectAtIndex:i] objectForKey:#"downloads"] integerValue];
s.downloads = value;
value = [[[statsForDate objectAtIndex:i] objectForKey:#"apps"] integerValue];
s.apps = value;
[statisticArray addObject:s];
}
[self.statistics setObject:statisticArray forKey:key];
};
}
I have found that autorelease in ststisticsResponse - resolves the problem:
NSMutableDictionary *statisticsResponse = [[jsonParser objectWithString:data]autorelease];
But then something fails in SBJsonStreamParserAccumulator.m in dealoc function.
What is the problem?
Note that the warnings about potential leaks come on the line after the potential leak, because that's the first point at which the referenced object is technically "leaked". So your current fixes are probably over-releasing and causing crashes.
The first statement in your question actually refers to a leak in this line, immediately before:
self.statistics = [[NSMutableDictionary alloc]init];
You've got no further reference to that allocated dictionary, and it's a retained property, so you have a leak.
self.statistics = [[[NSMutableDictionary alloc]init] autorelease];
Will fix that one. The next one, you have to release the jsonParser when you've finished with it (after the parsing is done):
[jsonParser release];
I'm not going to go through all of them but you should get the idea. Basically you need to read the memory management guide, or update to ARC.
Pay attention to the variable names in the warnings. They tell you where the leak is.
I have a Scenario , where i have to call a Method only once , whenever a User Will Update the Application or make a Fresh Install.
SO my Question is there is any particular Method to be called in App Delegate , After We update the Application , so if someone can tell me a another way to Achieve this , that would be really appreciated.
I would set a value in NSUserDefaults after you have called the function one time. See the accepted answer here: iOS : Call a method just one time
If you need to run after an update, you should include an always increasing number, or pull the build number, and check against the saved value. This will allow you to know if the app has been updated.
I am writing following function which uniquely checks if user has rated the current version, [self nowRate] is the function, please change this to whatever action you want to perform uniquely per version
-(void)rateApp {
NSString *version = [[[NSBundle mainBundle] infoDictionary] objectForKey:#"CFBundleShortVersionString"];
NSMutableDictionary*appRatedForVersion = [[NSMutableDictionary alloc] init];
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
if ([[[NSUserDefaults standardUserDefaults] dictionaryRepresentation].allKeys containsObject:#"AppRateDictionaryData"]){
NSData *versionRateData = [defaults objectForKey:#"AppRateDictionaryData"];
appRatedForVersion = [NSKeyedUnarchiver unarchiveObjectWithData:versionRateData];
if ([appRatedForVersion objectForKey:version] != nil) {
NSNumber *isAppRatedForCurrentVersion = [appRatedForVersion objectForKey:version];
BOOL hasBeenRated = [isAppRatedForCurrentVersion boolValue];
if (hasBeenRated) {
//Action already performed in this version do whatever you like
} else {
[self nowRate];
}
} else {
[appRatedForVersion setObject:[NSNumber numberWithBool:YES] forKey:version];
NSData *versionRateData1 = [NSKeyedArchiver archivedDataWithRootObject:appRatedForVersion];
[defaults setObject:versionRateData1 forKey:#"AppRateDictionaryData"];
[defaults synchronize];
[self nowRate];
}
} else {
[appRatedForVersion setObject:[NSNumber numberWithBool:YES] forKey:version];
NSData *versionRateData = [NSKeyedArchiver archivedDataWithRootObject:appRatedForVersion];
[defaults setObject:versionRateData forKey:#"AppRateDictionaryData"];
[defaults synchronize];
[self nowRate];
}
}
Why would the following implementation of the Dictionary cause a memory leak? See the screenshot below as well. Practically all of the leaks there are from this method.
- (void) setLocation:(NSString *) location:(NSString *) turnPage {
NSLog(#"Start setLocation");
//---get the path to the property list file---
NSString *localPlistFileNameConf = [[self documentsPath] stringByAppendingPathComponent:#"Config.plist"];
NSMutableDictionary *copyOfDict;
//---if the property list file can be found---
if ([[NSFileManager defaultManager] fileExistsAtPath:localPlistFileNameConf]) {
//---load the content of the property list file into a NSDictionary object---
NSDictionary *dict = [[NSDictionary alloc] initWithContentsOfFile:localPlistFileNameConf];
//---make a mutable copy of the dictionary object---
copyOfDict = [dict mutableCopy];
[dict release];
}
else {
//---load the property list from the Resources folder---
NSString *pListPath = [[NSBundle mainBundle] pathForResource:#"Config" ofType:#"plist"];
NSDictionary *dict = [[NSDictionary alloc] initWithContentsOfFile:pListPath];
//---make a mutable copy of the dictionary object---
copyOfDict = [dict mutableCopy];
[dict release];
}
location = [self checkLocationValidity:location:turnPage];
[copyOfDict setValue:location forKey:#"Location"];
[self writeConfigToFile:copyOfDict];
NSLog(#"End setLocation");
}
You're not releasing copyOfDict anywhere. You own any object created with a method that starts with copy, so you need to release those objects. It's probably misreporting the source as the original dictionary due to a bit of trickery in the NSDictionary class cluster for efficiency reasons. Try running analyse over your code, it should point these things out to you.
I'm starting objective-c development and I would like to ask the best way to implement a list of keys and values.
In Delphi there is the class TDictionary and I use it like this:
myDictionary : TDictionary<string, Integer>;
bool found = myDictionary.TryGetValue(myWord, currentValue);
if (found)
{
myDictionary.AddOrSetValue(myWord, currentValue+1);
}
else
{
myDictionary.Add(myWord,1);
}
How can I do it in objective-c? Is there equivalent functions to the above mentioned AddOrSetValue() or TryGetValue()?
Thank you.
You'd want to implement your example along these lines:
EDIT:
//NSMutableDictionary myDictionary = [[NSMutableDictionary alloc] init];
NSMutableDictionary *myDictionary = [[NSMutableDictionary alloc] init];
NSNumber *value = [myDictionary objectForKey:myWord];
if (value)
{
NSNumber *nextValue = [NSNumber numberWithInt:[value intValue] + 1];
[myDictionary setObject:nextValue forKey:myWord];
}
else
{
[myDictionary setObject:[NSNumber numberWithInt:1] forKey:myWord]
}
(Note: you can't store ints or other primitives directly in a NSMutableDictionary, hence the need to wrap them in an NSNumber object, and make sure you call [myDictionary release] when you've finished with the dictionary).
The other answers are correct, but there is more modern syntax for this now. Rather than:
[myDictionary setObject:nextValue forKey:myWord];
You can simply say:
myDictionary[myWord] = nextValue;
Similarly, to get a value, you can use myDictionary[key] to get the value (or nil).
Yep:
- (id)objectForKey:(id)key;
- (void)setObject:(id)object forKey:(id)key;
setObject:forKey: overwrites any existing object with the same key; objectForKey: returns nil if the object doesn't exist.
Edit:
Example:
- (void)doStuff {
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setObject:#"Foo" forKey:#"Key_1"]; // adds #"Foo"
[dict setObject:#"Bar" forKey:#"Key_2"]; // adds #"Bar"
[dict setObject:#"Qux" forKey:#"Key_2"]; // overwrites #"Bar"!
NSString *aString = [dict objectForKey:#"Key_1"]; // #"Foo"
NSString *anotherString = [dict objectForKey:#"Key_2"]; // #"Qux"
NSString *yas = [dict objectForKey:#"Key_3"]; // nil
}
Reedit: For the specific example there exists a more compact approach:
[dict
setObject:
[NSNumber numberWithInteger:([[dict objectForKey:#"key"] integerValue] + 1)]
forKey:
#"key"
];
Crazy indentation for readability.
This is my code: (customNames and customNamesArray are static variables)
-(void) loadCustomDataFromDisk
{
NSString *fullPath = [self filePathAndFileName: #"customData.plist"];
if ( ![[NSFileManager defaultManager] fileExistsAtPath: fullPath] )
{
NSLog(#"Loading file fails: File not exist");
customNames = [[NSMutableDictionary alloc] init];
customNamesArray = [[NSMutableArray alloc] init];
}
else
{
NSMutableDictionary *customItems = [[NSMutableDictionary alloc] initWithContentsOfFile: fullPath];
customNames = [customItems objectForKey: #"customNamesDict"];
customNamesArray = [customItems objectForKey: #"customNamesArray"];
if (!customItems)
NSLog(#"Error loading file");
[customItems release];
}
}
-(void) saveCustomDataToDisk
{
NSString *path = [self filePathAndFileName: #"customData.plist"];
NSMutableDictionary *customItems = [[NSMutableDictionary alloc] init];
[customItems setObject: customNames forKey: #"customNamesDict"];
[customItems setObject: customNamesArray forKey: #"customNamesArray"];
BOOL success;
success = [customItems writeToFile:path atomically:YES];
if (!success)
NSLog(#"Error writing file: customDataDict.plist");
[customItems release];
}
According to Build and Analyze, I have a potential leak in loading customItems
NSMutableDictionary *customItems = [[NSMutableDictionary alloc] initWithContentsOfFile: fullPath];
true enough, according to Instruments, I do have a leak in that part. But when I tried release or autoreleasing customItems, my app crashes. Even if I change NSMutableDictionary to NSDictionary, I still have the leak.
How do I fix this?
Any help would be very much appreciated. :) Thanks :)
You have to retain customNames and customNamesArray because you are using reference from dictionary customItems and after passing reference you are releasing it.
customNames = [[customItems objectForKey: #"customNamesDict"] retain];
customNamesArray = [[customItems objectForKey: #"customNamesArray"] retain];
Now you can release customItems.
Your code is right as I can see. You can see answer here and may be it helps - Leak problem with initWithContentsOfFile
I have only one question: You create NSString *fullPath and never release it. Is it autoreleased string? If so - your code is fine.