Re: Passing param by reference then using within block throws exception
Re: Passing param by reference then using within block throws exception
- Subject: Re: Passing param by reference then using within block throws exception
- From: "Gary L. Wade" <email@hidden>
- Date: Thu, 22 Sep 2016 12:45:09 -0700
Look at these two lines:
> __block NSString* noFillMeIn;
...
> *noFillMeIn = @"wow";
Unless the original code is correct, you've got mismatched pointers, and you should try turning on more warnings and reading what they say, as well as trying the analyzer.
--
Gary L. Wade (Sent from my iPhone)
http://www.garywade.com/
> On Sep 20, 2016, at 2:06 PM, Steve Mills <email@hidden> wrote:
>
> I'm turning on ARC for a project (yay) and have run into a problem I can't wrap my head around. It always worked fine before ARC. When I turn zombies on, doing "memory history 0x610004279ac0" can't find it in the history. Here's the method and the call to it:
>
> -(void) doStuff:(NSString**)fillMeIn
> {
> [array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL* stop) {
> if(obj.flag) {
> *stop = YES;
> *fillMeIn = @"wow";
> }
> }];
> }
>
> NSString* getFilledIn;
>
> [thing doStuff:&getFilledIn];
>
> The call to doStuff: results in EXC_BAD_ACCESS, or "*** -[CFString retain]: message sent to deallocated instance 0x610004279ac0" if I turn zombies on.
>
> I tried changing the param type to (NSString** _Nonnull), thinking it was confused about my knowing that the reference will never be nil, but it didn't help. Then I got to thinking about the reference being assigned inside the block and changed it to:
>
> -(void) doStuff:(NSString** _Nonnull)fillMeIn
> {
> __block NSString* noFillMeIn;
>
> [array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL* stop) {
> if(obj.flag) {
> *stop = YES;
> *noFillMeIn = @"wow";
> }
> }];
>
> *fillMeIn = noFillMeIn;
> }
>
> That seems to fix it. Is there a better way to deref and assign to the param from within the block?
>
> Sent from iCloud's ridiculous UI, so, sorry about the formatting
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