Question

I used the codes below to set a NSString

#import <Foundation/Foundation.h>

@interface AppController : NSObject
{


    NSString *myString;


}

@property (nonatomic, retain) NSString *myString;
@end

#import "AppController.h"


@implementation AppController
@synthesize myString;

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {

    NSString *zs0= [[NSString alloc] initWithFormat: @"abc"];
    myString =[zs0 retain];
    [zs0 release];//breakpoint

}

- (void)dealloc {


    [myString release];


    [super dealloc];
}




@end

when I check the value of myString at the breakpoint
it always said ‘out of scope’

Welcome any comment

Answer 1

1. You don’t need the temp variable zs0 – just assign it to the property
2. You don’t need initWithFormat since you’re not formatting.
3. You don’t need to alloc the string – if you call [NSString stringWithString] it will autorelease it and then when you assign it to a (retain) property, it will retain it.
4. You’re over retaining. You alloc the string which gives it a retain count of 1, then you retain it which gives it 2, then you assign it to a retained property which retains it again.

One simple way is:

self.myString = [NSString stringWithString:@"abc"];

That will create a string that’s autoreleased (not created with alloc, copy by convention) and then the property will retain it.