On 18 Oct 2011, at 00:29, glenn andreas wrote:
>
> On Oct 16, 2011, at 1:58 AM, Gerriet M. Denkmann wrote:
>
>> I have this code:
>>
>> for( id aThing in someArray )
>> {
>> if ( [ aThing respondsToSelector: @selector(setTitle:) ] )
>> {
>> [ self replaceIn: aThing
>> readSelector: @selector(title)
>> writeSelector: @selector(setTitle:)
>> withTable: tableName
>> ];
>> }
>> }
>>
>>
>> - (void)replaceIn: thing readSelector: (SEL)selectorIn writeSelector:
>> (SEL)selectorOut withTable: (NSString *)tableName;
>> {
>> NSString *key = [ thing performSelector: selectorIn ];
>> ...
>> NSString *rep = ...
>> [ thing performSelector: selectorOut withObject: rep ];
>> }
>>
>> Now, using Arc I am told that "PerformSelector may cause a leak because its
>> selector is unknown".
>> What I am supposed to do about this? I really want to have code without
>> warnings.
>
>
> Based on your samples, why not change this to just use KVC instead?
>
> for (id aThing in someArray)
> if ([aThing respondsToSelector: @selector(setTitle:)]) { // too bad
> there isn't a cleaner way to ask [aThing hasKey: @"title"]
> [ self replaceIn: aThing key: @"title" withTable: tableName ];
> }
> }
>
> - (void) replaceIn: (id) thing key: (NSString *) ivarKey withTable: (NSString
> *) tableName
> {
> NSString *key = [thing valueForKey: ivarKey];
> ...
> NSString *rep = ...
> ...
> [ thing setValue: rep forKey: ivarKey];
> }
>
This looks like a very good idea.
I will try it tomorrow.
How does:
> NSString *key = [thing valueForKey: ivarKey];
compare performance-wise with:
>> NSString *key = [ thing performSelector: selectorIn ];
Not that it matters here - these lines will be executed a few dozen times.
But I just want to know.
Kind regards,
Gerriet.
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