I'm struggling to fix a memory leak in a helper function I have made. The helper function takes the result of
+ (id)JSONObjectWithData:(NSData *)data options:(NSJSONReadingOptions)opt error:(NSError * _Nullable *)error
and converts all the leaf elements into NSStrings if they are NSNumbers.
Here is the method:
-(NSArray *) stringisizeObjects:(NSArray *)inputArray{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSMutableArray *mutable = [[NSMutableArray alloc] initWithCapacity:[inputArray count]];
for (int i = 0; i < [inputArray count]; i++) {
NSArray *keys = [inputArray[i] allKeys];
NSMutableDictionary *addDictionary = [[NSMutableDictionary alloc] initWithCapacity:[keys count]];
for (int j = 0; j < [keys count]; j++) {
id theObject = [[inputArray[i] objectForKey:keys[j]]autorelease];
if ([theObject isKindOfClass:[NSNumber class]]) {
[addDictionary setObject:[theObject stringValue] forKey:keys[j]];
[theObject release];
}else if ([theObject isKindOfClass:[NSString class]]){
[addDictionary setObject:[inputArray[i] objectForKey:keys[j]] forKey:keys[j]];
}
}
[mutable addObject:addDictionary];
}
NSArray *returnArray = [mutable copy];
[mutable removeAllObjects];
[mutable release];
[pool drain];
return returnArray;
}
Here is how I get the input array.
id parsedThingy = [NSJSONSerialization JSONObjectWithData:resultJSONData options:1 error:&jsonDecodeError];
Before I can pass the result to my stringisize method I must ensure that I have an NSArray of NSDictionaries with matching keys.
NSArray *resultArray = [self stringisizeObjects:parsedThingy];
The X-Code memory leaks tool has pointed me to this method as the cause of my problem.
Instruments showing leaks
As you can see I have tried wrapping things in autorelease pools, autoreleasing and releasing. I just don't see any way forward here.
This is a non ARC project that runs 24/7.
Edit: I took the advice from Droppy and tried to re-write the method using mutableCopy. The leak is still there. At this point my only work around maybe to change the source of the JSON to send only strings. :(
-(NSArray *) stringisizeObjects2:(NSArray *)inputArray{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSMutableArray *mutableArray = [inputArray mutableCopy];
for (int i = 0; i < [mutableArray count]; i++) {
NSMutableDictionary *mutableDict = [mutableArray[i] mutableCopy];
NSArray *keys = [mutableDict allKeys];
for (int j = 0; j < [keys count]; j++) {
if ([[mutableDict objectForKey:keys[j]] isKindOfClass:[NSNumber class]]) {
NSString *stringValue = [[mutableDict objectForKey:keys[j]] stringValue];
[mutableDict removeObjectForKey:keys[j]];
[mutableDict setObject:stringValue forKey:keys[j]];
}
}
mutableArray[i] = [mutableDict copy];
[mutableDict release];
}
NSArray *returnArray = [mutableArray copy];
[mutableArray release];
[pool drain];
return returnArray;
}
problem:
addDictionary called alloc but not call release or autorelease
returnArray = [mutable copy]; // did increase retainCount +1, need autorelease here
id theObject = [inputArray[i] objectForKey:keys[j]]; // not need autorelease or release for object that You not own
add NSAutoreleasePool to top an bottom here just do nothing
solution:
-(NSArray *) stringisizeObjects:(NSArray *)inputArray{
NSMutableArray *mutable = [[NSMutableArray alloc] initWithCapacity:[inputArray count]];
for (int i = 0; i < [inputArray count]; i++) {
NSArray *keys = [inputArray[i] allKeys];
NSMutableDictionary *addDictionary = [[NSMutableDictionary alloc] initWithCapacity:[keys count]];
for (int j = 0; j < [keys count]; j++) {
id theObject = [inputArray[i] objectForKey:keys[j]]; // not need autorelease
if ([theObject isKindOfClass:[NSNumber class]]) {
[addDictionary setObject:[theObject stringValue] forKey:keys[j]];
//[theObject release]; // not need release value here
}else if ([theObject isKindOfClass:[NSString class]]){
[addDictionary setObject:[inputArray[i] objectForKey:keys[j]] forKey:keys[j]];
}
}
[mutable addObject:addDictionary];
[addDictionary release]; // release after not use
}
NSArray *returnArray = [[[NSArray alloc] initWithArray:mutable] autorelease]; // auto release for return value
[mutable removeAllObjects];
[mutable release];
return returnArray;
}
I have an NSmutable array and I am adding some strings present in the C array to it. By using this method
if (!self.arrayOfVariableNames) {
self.arrayOfVariableNames = [[NSMutableArray alloc] init];
for (int i = 0; i< cols; i++) {
[self.arrayOfVariableNames addObject:[NSString stringWithCString:cArrayOfVariableNames[i] encoding:NSUTF8StringEncoding ]];
}
}
else{
[self.arrayOfVariableNames removeAllObjects];
for (int i = 0; i< cols; i++) {
[self.arrayOfVariableNames addObject:[NSString stringWithCString:cArrayOfVariableNames[i] encoding:NSUTF8StringEncoding ]];
}
}
Does this method ensure that the objects in the NSmutableArray won't be deallocated when the C array is taken out of memory?
if this array arrayOfVariableNames is becoming Null, then the problem is with the initialisation of the array. Please try to use Lazy loading by doing this:
- (NSArray*)arrayOfVariableNames {
if (!_arrayOfVariableNames) {
_arrayOfVariableNames = [[NSMutableArray alloc] init]; //initialise the array if needed
}
return _arrayOfVariableNames; //else return the already initialized array
}
and please comment out this line in your code: self.arrayOfVariableNames = [[NSMutableArray alloc] init];
****EDIT****
Please find the update code in https://docs.google.com/file/d/0BybTW7Dwp2_vdHhQN1p1UzExdTA/edit?pli=1. Have a look at it.
Yes. NSArray retains anything in it.
But you should stop chaining your NSString creation and instead creat a string a line before adding it to the array. Then check for nil.
Only add it to the array if it is not nil.
Do code defensively.
arrayOfVariableNames will not change when the C array get deallocated.
Make sure that your arrayOfVariableNames variable is strong.
#property (nonatomic, strong) NSMutableArray *arrayOfVariableNames;
if (!self.arrayOfVariableNames)
{
self.arrayOfVariableNames = [[NSMutableArray alloc] init];
}
else
{
[self.arrayOfVariableNames removeAllObjects];
}
for (int i = 0; i< cols; i++)
{
NSString *tempString = [NSString stringWithCString:cArrayOfVariableNames[i] encoding:NSUTF8StringEncoding];
if([tempString length] > 0)
{
[self.arrayOfVariableNames addObject:tempString];
}
else
{
NSLog(#"string is empty");
}
}
#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
#autoreleasepool {
NSMutableString *outputStringSet = [[NSMutableString alloc] init];
NSMutableString *outputStringArray = [[NSMutableString alloc] init];
NSMutableSet *mySet = [[NSMutableSet alloc] init];
NSMutableArray *myArray = [[NSMutableArray alloc] initWithCapacity: 10];
int userInput;
NSLog(#"Enter 10 numbers");
for( int i = 0; i < 10; i++) {
scanf("%i", &userInput);
NSNumber *input = [[NSNumber alloc] initWithInt: userInput];
[myArray addObject:input];
if([mySet member: input]) {
[mySet addObject: input];
}
}
for (int k = 0; k < [myArray count]; k++) {
[outputStringArray appendFormat:#"%#, ", [myArray objectAtIndex:k]];
}
NSLog(#"%#", [outputStringArray substringToIndex:[outputStringArray length] - 2]);
for (int j = 0; j < [myArray count]; j++) {
if([mySet containsObject: [myArray objectAtIndex:j]]) {
[outputStringSet appendFormat:#"%#, ", [myArray objectAtIndex:j]];
}
NSLog(#"%#", outputStringSet);
}
}
return 0;
}
Code above prints the array but not the appropriate object in the set
Why?
Please explain clearly. I am a bit of a noob, and couldnt find the answer anywhere else.
thanks
if([mySet member: input]) {
[mySet addObject: input];
}
You're adding the object to the set if it’s already in it. You want the reverse: add the object if it's not in it.
Thus:
if ( ! [mySet member:input] )
[mySet addObject:input];
By the way, you should use containsObject: instead of member: in your test:
containsObject:
Returns a Boolean value that indicates whether a given
object is present in the set.
- (BOOL)containsObject:(id)anObject
Edit: you don't even need to test if the object is already in the set before adding it. After all, that's the main purpose of a NSSet: to ensure uniqueness of its objects. So if you add an object twice, the second call will silently be ignored, as the object is alreay in it.
Your set is empty because of
if([mySet member: input]) {
[mySet addObject: input];
}
member:
Determines whether the set contains an object equal to a given object,
and returns that object if it is present.
Sorry for the simple question, but I am self taught and know that there are gaps in my education.
To print an array in objective C, I believe is:
NSLog(#"My array: %#", myArray);
How can I print an array of arrays?
Thanks
You want this:
for(NSArray *subArray in myArray) {
NSLog(#"Array in myArray: %#",subArray);
}
This will work for an array that has arrays nested one level deep.
You don't need to do anything different to log an array of arrays; the code exactly as you've written it will already show the contents of the sub-arrays.
That is, the following program:
#import <Foundation/Foundation.h>
int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
NSMutableArray *array = [NSMutableArray array];
for (int i=0; i<5; ++i) {
NSMutableArray *sub = [NSMutableArray array];
for (int j=0; j<=i; ++j) {
[sub addObject:[NSString stringWithFormat:#"%d", j]];
}
[array addObject:sub];
}
NSLog(#"Array: %#", array);
[pool drain];
return 0;
}
Produces the following output:
Array: (
(
0
),
(
0,
1
),
(
0,
1,
2
),
(
0,
1,
2,
3
),
(
0,
1,
2,
3,
4
)
)
Clearly, it's already logging the sub-arrays just fine. If you want to control the formatting differently, you'd have to manually iterate them, but by default, the -description of an NSArray is little more than the -description of every object in that array, which includes all sub-arrays.
So I was embarrassed by the recursiveDescription thing, so I wrote my own as a category on NSArray. Note that this code will print out a description for an array of arrays to any depth. The description itself could probably use a bit more formatting than commas and newlines. Here you go:
#interface NSArray (RecursiveDescription)
- (NSString *)recursiveDescription;
#end
#implementation NSArray (RecursiveDescription)
- (NSString *)recursiveDescription {
NSMutableString *description = [[NSMutableString alloc] initWithString:#"Array (\n"];
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
for (NSObject *child in self) {
if ([child respondsToSelector:#selector(recursiveDescription)]) {
[description appendFormat:#"%#,\n", [child recursiveDescription]];
}
else {
[description appendFormat:#"%#,\n", [child description]];
}
}
[pool drain];
[description appendString:#"\n)"];
return [description autorelease];
}
#end
Try logging the return value from NSArray's -description method.
NSLog(#"My array: %#", [myArray description]);
Moreover, for print all of elements
int i = 0;
int j = 0;
for(NSArray *subArray in myArray) {
NSLog(#"[%d] %#",i, subArray);
j =0;
for(NSObject *element in subArray) {
NSLog(#"[%d:%d] %#", i,j,element);
++j;
}
++i;
}
As much as I like how easy it is to log out an object in Objective-C, I didn't like seeing a 2D array as a very long list. I created a category on NSArray that prints out 2D arrays. It's not perfect and can be improved, but it has worked for me.
Header:
#interface NSArray (Logging)
- (void)log2DArray;
#end
Implementation:
#import "NSArray+Logging.h"
#implementation NSArray (Logging)
- (void)log2DArray {
NSMutableString *formattedString = [[NSMutableString alloc] init];
NSInteger longestSubarrayLength = 0;
for (NSArray *subarray in self) {
if (subarray.count > longestSubarrayLength) {
longestSubarrayLength = subarray.count;
}
}
for (int i = 0; i < longestSubarrayLength; i++) {
[formattedString appendFormat:#"\n"];
for (int j = 0; j < self.count; j++) {
NSArray *tempArray = [self objectAtIndex:j];
if (tempArray.count <= longestSubarrayLength) {
[formattedString appendFormat:#"%#\t", [tempArray objectAtIndex:i]];
} else {
[formattedString appendFormat:#"\t"];
}
}
}
NSLog(#"%#", formattedString);
}
#end
Usage:
[myArray log2DArray];
Or use recursiveDescription :)
NSLog(#"my arrays: %#", [myArray recursiveDescription]);
I am getting memory leak in NSMutableArray allocation.. in
NSMutableArray *contactsArray =[[NSMutableArray alloc] init];
CODE:
+(NSMutableArray*)getContacts
{
addressBook = ABAddressBookCreate();
NSArray* peopleArray = (NSArray*) ABAddressBookCopyArrayOfAllPeople(addressBook);
int noOfPeople = [peopleArray count];
NSMutableArray *contactsArray =[[NSMutableArray alloc] init];
for ( int i = 0; i < noOfPeople; i++)
{
ABRecordRef person = [peopleArray objectAtIndex:i];
ABRecordID personId = ABRecordGetRecordID(person);
NSString* personIdStr = [NSString stringWithFormat:#"%d", personId];
ContactDTO* contactDTO = [AddressBookUtil getContactDTOForId:personIdStr];
[contactsArray addObject:contactDTO];
}
[peopleArray release];
return contactsArray;
}
It is standard procedure that objects returned from methods (in your case, contactsArray) are autoreleased before returning.
You could either return [contactsArray autorelease]; or create it already autoreleased with [NSMutableArray arrayWithCapacity:noOfPeople]
You need to release contactsArray manually somewhere, because it does not define autorelease.