Hi,
I was confused by this:
> It also doesn't make sense to synchronize on the myDict object. That's what
> is in flux. You should synchronize on "self", the object which owns and
> manages myDict.
Surely as long as every access to the dictionary is @synchronized to the same
entity it’s fine?
The way I’d atcheive this is to make the NSMutableDictionary a private property:
@property (nonatomic,strong) NSMutableDictionary* pDictX;
and define public methods:
-(void) removeObjectFromDictXWithKey:(NSString*) theKey;
-(void) addObject:(id) theObject toDictXWithKey:(NSString*) theKey;
-(id) getObectFromDictXWithKey:(NSString*) theKey;
The body of these methods would encapsulated with @synchronized :
@synchronized (self. pDictX)
{
// Code to Access self.pDictX
}
If you wanted two dictionaries to work in this pay, just define another set for
pDictY, etc.
Surely if you do @synchronized(self) then access to pDictX will be blocked
needlessly by access to pDictY?
Cheers
Dave
On 1 Apr 2014, at 14:45, Trygve Inda <cocoa...@xericdesign.com> wrote:
>> On Apr 1, 2014, at 12:25 AM, Jens Alfke wrote:
>>
>>> On Mar 31, 2014, at 10:16 PM, Trygve Inda <cocoa...@xericdesign.com> wrote:
>>>
>>>> I need to be able to set a new myDict and not have it happen between the
>>>> reading of different values from the dictionary by other threads.
>>>
>>> Don’t expose the dictionary in mutable form. You can’t make that thread-safe
>>> unless all the clients voluntarily agree to do something like wrap their
>>> usage with @synchronized blocks using the dictionary as a parameter.
>>
>> I didn't see mention of mutating the dictionary. It sounds like he's just
>> using a setter to replace it (which also likely releases it, which makes it
>> potentially unsafe).
>>
>> I agree, though, that properties should almost never be of mutable type. But
>> making them immutable doesn't, by itself, create thread-safety. If nothing
>> else, the owner could still mutate it while other threads are reading it.
>>
>> Regards,
>> Ken
>>
>>
> Yes, the property is Mutable in the host app, but after being sent to the
> helper app (which has multiple threads), it could just as easily be an
> NSDictioanary (non-mutable).
>
> I just need to be 100% certain that when the helper app threads read two
> values from the dictionary, that the dictionary does not change between (or
> during) these two reads.
>
> T.
>
>
>
>
>
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