On Aug 9, 2008, at 5:24 PM, Dennis Harms wrote:
I've created a class with some member variables of type NSString*.
In the
init function of the class, I write something into those strings.
Now I call
a function of the initialized class instance as a new thread and
try to read
from those member variables. This leads to a crash... Can someone
give me a
hint as to why this won't work?
Here's my code, shrunk down to just the problematic part:
-- MyClass.h -
@interface MyClass: NSObject
{
@private
NSString* baseURL;
}
- (id) initWithHost: (NSString*) _url;
- (void) doSomething: (id) object;
@end
--
-- MyClass.m -
@implementation MyClass
- (id) initWithHost: (NSString*) _url
{
self = [super init];
baseURL = [NSString stringWithString: _url];
One thing I notice right off is that you're initializing an instance
variable using a method that creates an autoreleased string, which
will go away next time through the application's event loop. How
about baseURL = [_url retain]; instead? If the string pointed to by
_url is really immutable, you just need to increment the retain count
so it'll continue to exist for the lifetime of your object (and then
be sure to call [_url release] in your object's dealloc method so you
don't leak memory).
return self;
}
- (void) doSomething: (id) object
{
NSString *url = [NSString stringWithString: baseURL]; // --
the crash
occurs even when just reading the member
You might check that baseURL is still valid just before executing
this statement when you have your app set up to execute this in other
than the main thread. Making the change, above, will likely fix the
crash.
Also, why are you calling -stringWithString: here? You already have a
perfectly good string in baseURL. Use it directly.
}
@end
--
I've tried calling the function in the same thread, as well as three
different ways of calling it in a seperate thread. Every time there's
another thread involved, it crashes when accessing the member
variable. If
the function doesn't access any members, the code works just fine...
instance = [[MyClass alloc] initWithHost: txtHost.text];
[instance doSomething: nil]; // Works
[instance performSelectorInBackground: @selector(doSomething:)
withObject:
nil]; // Doesn't work
[[[NSThread alloc] initWithTarget: instance selector:
@selector(doSomething:) object: nil] start]; // Doesn't work
[NSThread detachNewThreadSelector: @selector(doSomething:) toTarget:
instance withObject: nil]; // Doesn't work
___
Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com
This email sent to [EMAIL PROTECTED]
