Leaks Performance Tool not detecting an obvious memory leak - objective-c

Question

To give the short version of the story here, I'm trying to make an example of a memory leak and why you would want to use the leaks performance tool in the Instruments application. I need to use this method of detecting memory leaks, but the example that I've created is not creating any memory leaks that the tool detects (yes, apparently I'm failing at failing here -_-). Here's the code:
// Memory_Leak_ExampleViewController.h
// Memory Leak Example
#import <UIKit/UIKit.h>
#import "StringReturner.h"
#interface Memory_Leak_ExampleViewController : UIViewController {
IBOutlet UITextField* xTF;
IBOutlet UITextField* yTF;
IBOutlet UITextView* result;
StringReturner* sr;
}
-(IBAction)addTogether;
-(IBAction)releaseSR;
#end
// Memory_Leak_ExampleViewController.m
// Memory Leak Example
#import "Memory_Leak_ExampleViewController.h"
#implementation Memory_Leak_ExampleViewController
- (void)viewDidLoad {
[super viewDidLoad];
sr = [[StringReturner alloc] initWithFrame:self.view.frame];
}
- (IBAction)addTogether
{
[result setText:[sr returnEq:[xTF.text intValue]:[yTF.text intValue]]];
}
- (IBAction)releaseSR
{
[sr release];
}
#end
//StringReturner.h
#import <UIKit/UIKit.h>
#interface StringReturner : UIView {
NSString* string;
NSString* returnString;
}
-(NSString*)returnEq:(int)x:(int)y;
#end
// StringReturner.m
#import "StringReturner.h"
#implementation StringReturner
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
}
return self;
}
- (NSString*)returnEq:(int)x:(int)y
{
string = [[NSString alloc] initWithString:#""];
int result = x+y;
string = [NSString stringWithFormat:#"%d + %d = %d", x, y, result];
return string;
}
- (void)dealloc {
[super dealloc];
}
#end
All of the IBActions and IBOutlets are set up correctly, so shouldn't there be a memory leak after adding once and then releasing the instance of StringReturner? If not, what am I not doing wrong?

Answer 1

Initializing NSString with static strings like #"" doesn't result in a real string being allocated and put on heap so Leaks doesn't detect it. It's an optimization.
Try leaking the other string created by stringWithFormat. Instruments Leaks will pick that up right away. Put a [string retain] after string = [NSString stringWithFormat:#"%d + %d = %d", x, y, result]; to create the leak.