I have an NSArray which has the properties nonatomic and retain. What I would like to know is am I initialising it in the correct way so that the retain count is what it should be?
The _lengthArr is the #synthesized ivar of lengthArr in my.h
#synthesize lengthArr = _lengthArr;
_lengthArr = [[NSArray arrayWithObjects:#"10 Minutes", #"20 Minutes", #"30 Minutes", #"1 Hour", #"2 Hours", #"5 Hours", #"5 Hours +", nil] retain];
You are assigning to an ivar there, so the code you posted will do what you want. You could also use _lengthArr = [[NSArray alloc] initWithObjects:...], which would avoid a useless autorelease.
Or you could do self.lengthArr = [NSArray arrayWithObjects:...] to allow the setter to automatically retain it, although it is recommended to avoid this in initialization methods.
Related
Is there a memory leak withOUT ARC?
NSMutableArray *array = [[NSMutableArray alloc] init];
NSNumber *numberForTest = [[NSNumber alloc] initWithInt:123456];
[array addObject: numberForTest];
[numberForTest release];
NSLog(#"number = %#", numberForTest); //safe to access "numberForTest" after calling release???
[array release];
My concern is: Did
[array addObject: numberForTest];
make "numberForTest" not qualified to be deallocated, before
[array release];
???
After using Static Analyzer, no leak is reported. And the output is consistently correct. But I don't feel comfortable.
NSArray (and NSMutableArray) retain objects.
When you release your array, all the objects in that array get released as well.
I have a NSMutableArray that is loaded with a inforamtion from a dictionary...
[self.data removeAllObjects];
NSMutableDictionary *rows = [[NSMutableDictionary alloc] initWithDictionary:[acacheDB.myDataset getRowsForTable:#"sites"]];
self.data = [[NSMutableArray alloc] initWithArray:[rows allValues]];
There are two key value pairs in the rows dictionary.
I need to sort the self.data NSMutableArray in alphabetical order.
How is this accomplished??
thanks
tony
If the values are plain strings you can use the following to create a sorted array:
NSArray *sorted = [values sortedArrayUsingSelector:#selector(caseInsensitiveCompare:)];
This should do:
[self.data removeAllObjects];
NSArray *values = [[acacheDB.myDataset getRowsForTable:#"sites"] allValues];
NSSortDescriptor *alphaDescriptor = [[NSSortDescriptor alloc] initWithKey:#"DCFProgramName" ascending:YES selector:#selector(localizedCaseInsensitiveCompare:)];
NSArray *sortedValues = [values sortedArrayUsingDescriptors:[NSMutableArray arrayWithObjects:alphaDescriptor, nil]];
[alphaDesc release];
[self.data addObjectsFromArray:sortedValues];
There's no need to clear an NSMutableArray if you're replacing it shortly afterwards.
There's no need to create an additional NSMutableDictionary, if you're not modifying anything in it.
There's no need to create an additional NSMutableArray, if you could just as well just add the values to the existing one.
Also: There are some serious memory leaks in your code. (2x alloc + 0x release = 2x leak)
Edit: updated code snippet to reflect OP's update on data structure.
I have an NSMutableArray i am trying to convert into a string.
Declaring my NSMutableArray...
NSMutableArray *listData;
And later inside a method...
NSString *foo = [listData componentsJoinedByString:#"|"];
NSLog(#"%#",foo);
It seems no matter what i try i keep getting EXC_BAD_ACCESS.
To make sure each element in my array was an NSString i also tried this...
NSMutableArray *mArray = [[NSMutableArray alloc] init];
for (id ln in listData) {
NSString *boo = [NSString stringWithFormat: #"%#",ln];
[mArray addObject:boo];
}
NSString *foo = [mArray componentsJoinedByString:#"|"];
NSLog(#"%#",foo);
I can manipulate my NSMutableArray by adding/deleting objects in the same method or other methods inside my class. But when i try "componentsJoinedByString" the error pops up. Does anyone have any advice or another way i can combine this array into a single NSString?
In the code you've given, there will never be an NSMutableArray for listData. At some point in your code, you'll need to create one, and presumably populate it.
Edit
Okay, so you may get into memory management problems here, so let's be a bit clearer:
You're synthesizing getters and setters for the instance variable, so it's good practice to use those to access it, they'll take care of retain and releasing appropriately.
To set listData you can simply use
self.listData = [listManage getList:[[NSUserDefaults standardUserDefaults] stringForKey:#"list_name"] list:#"LIST"];
or
[self setListData:[listManage getList:[[NSUserDefaults standardUserDefaults] stringForKey:#"list_name"] list:#"LIST"]];
if you prefer.
If i declare an NSArray with alloc & retain in single sentence then should i release the NSArray object twice (i.e. [arrayObject release] 2 times) ?
If you are creating an NSArray with an alloc and a retain on the same line then you are probably doing something wrong.
Objects are alloced with a retain count of +1, so there is no need to call retain on it as well.
To answer your question directly; yes, you do have to release it twice. Once because you created the object and once because you retained it. But I would question why you need to retain it an extra time in the first place.
You don't need to retain it. You already retain--or take ownership of--an object when you alloc/init. Revisit the Memory Management Programming Guide for Cocoa.
No, you have to release the object for each alloc and each retain. (And you can't alloc an object more than 1 time anyway.)
If you do
NSArray* arrayObject;
arrayObject = [[NSArray alloc] init];
arrayObject = [[NSArray alloc] init];
...
then it just wrong code. The latter assignment will cover the old one, which causes a leak. Either use 2 objects, and release each of them once:
NSArray* arrayObject1, arrayObject2;
arrayObject1 = [[NSArray alloc] init];
arrayObject2 = [[NSArray alloc] init];
...
[arrayObject1 release];
[arrayObject2 release];
or release the object before another init.
NSArray* arrayObject;
arrayObject = [[NSArray alloc] init];
...
[arrayObject release];
arrayObject = [[NSArray alloc] init];
...
[arrayObject release];
I can't seem to find an easy way to do it. The exact thing I need is:
[NSString stringWithFormat:#"%d doodads", n];
Where n is an int. So for 1234 I'd want this string (under my locale):
#"1,234 doodads"
Thanks.
For 10.6 this works:
NSNumberFormatter* numberFormatter = [[NSNumberFormatter alloc] init];
[numberFormatter setFormatterBehavior: NSNumberFormatterBehavior10_4];
[numberFormatter setNumberStyle: NSNumberFormatterDecimalStyle];
NSString *numberString = [numberFormatter stringFromNumber: [NSNumber numberWithInteger: i]];
And it properly handles localization.
I have recently discovered this one-liner:
[#1234567 descriptionWithLocale:[NSLocale currentLocale]]; // 1,234,567
Or in Swift 2:
1234567.descriptionWithLocale(NSLocale.currentLocale()) // 1,234,567
Swift 3/4:
(1234567 as NSNumber).description(withLocale: Locale.current)
Formatted per the question:
[#(n) descriptionWithLocale:[NSLocale currentLocale]];
Formatted without Objective-C literals:
[[NSNumber numberWithInt:n] descriptionWithLocale:[NSLocale currentLocale]];
This is the solution I was looking for when I asked the question. Available since iOS 2.0 and OS X 10.0, documented to return a string version of the number formatted as per the locale provided. stringValue is even documented to use this method but passing nil.
Seeing as it is my question and this fits my answer best, I am tempted to change the tick, but it seems cruel. Update I changed the tick, this answer is the answer.
The below doesn't address the locale, but it is a better way (in my opinion) of setting the thousand separator on the number formatter.
NSNumberFormatter *numberFormat = [[[NSNumberFormatter alloc] init] autorelease];
numberFormat.usesGroupingSeparator = YES;
numberFormat.groupingSeparator = #",";
numberFormat.groupingSize = 3;
Todd Ransom answered this perfectly.
I would just like to add (in a separate comment, so I can show some nicely formatted code), that if you plan to do this regularly, it's worth creating an NSString helper class.
So, create yourself an NSStringHelper.h containing this:
#import <Foundation/Foundation.h>
#interface NSString (NSStringHelper)
+(NSString*)formatWithThousandSeparator:(NSInteger)number;
#end
..and an NSStringHelper.m file containing this:
#import "NSStringHelper.h"
#implementation NSString (NSStringHelper)
+(NSString*)formatWithThousandSeparator:(NSInteger)number
{
// Format a number with thousand seperators, eg: "12,345"
NSNumberFormatter* numberFormatter = [[NSNumberFormatter alloc] init];
[numberFormatter setFormatterBehavior: NSNumberFormatterBehavior10_4];
[numberFormatter setNumberStyle: NSNumberFormatterDecimalStyle];
NSString *result = [numberFormatter stringFromNumber:[NSNumber numberWithInteger:number]];
return result;
}
#end
This gives you the perfect way to reuse this code in future projects.
#import "NSStringHelper.h"
NSInteger numOfUsers = 12345;
NSString* strNumberOfUsers = [NSString formatWithThousandSeparator:numOfUsers];
Cool, hey ?
Again, apologies for reposting Todd's answer (which was exactly what I was looking for !), but this is a great way to solve the problem, and have it ready to be used in your future XCode projects.
Use an NSNumberFormatter.