objective c - objc: strong property with NSString -

i declare strong property:

@property (strong) nsstring *message;

and set message like:

 self.message = [nsstring stringwithformat:@"xxxx %@",sth]; 

but crashed message:

 *** -[cfstring retain]: message sent deallocated instance 0x1015ea790 

even change property: strong-> copy, still crashes. fixed using:

 self.message = [[nsstring stringwithformat:@"xxxx %@",sth] copy]; 

but still can't understand write in same way in ios.

by way: code cocoa, no-arc

update1:

1 have added @synthesize message;

2 sth example, real code

self.message = [nsstring stringwithformat:@"xxxx %@", [[nsdate date] description]];

3 remember default implementation strong/copy property can like:

 - (void)setmessage:(nsstring*)newmsg {    if (message != newmsg)    {         [newmsg retain];         [message release];         message = newmsg;    } } 

so think property-synthesis add copy/retain me. that's makes me confused!

the negative reference count imbalance lies in code has not been posted.

this variant wrong:

self.message = [[nsstring stringwithformat:@"xxxx %@",sth] copy]; 

-- introduces positive reference count imbalance (hallmark side effect: leaked objects).

first, fix analyzer warnings. if not fix it, run instruments. can record reference count operations each object: debugging exec_bad_access on iphone using performance tool, allocations

note not solve problem: should use copy nsstring property rather strong.