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PONSDictionary and NSString, several messages return a strange value
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  1. PONSDictionary and NSString, several messages return a strange value
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    copied!<p>I am going crazy with a problem which I cannot understand at all! I have a NSDictionary (named 'headers') with NSString objects as values. In this dictionary are stored header fields obtained from a HTTP response.</p> <p>I need to send a message to this dictionary with this code</p> <pre><code>NSString* cacheControlString = [headers valueForKey:@"Cache-Control"] </code></pre> <p>this message is sent inside a method which is called three times... what I have is that the first and the second time the message returns a correct value. The third time SOMETIMES it does not return a correct value, and debugger says about cacheControlString</p> <pre><code>@&lt;variable is not a NSString&gt; </code></pre> <p>But WHY?!?! and why not always? That method does not modify the dictionary, because it cannot see the dictionary! In order to be sure that I have full control on that dictionary I copied the headers returned by the response in another dictionary created by me.</p> <p>The other strange thing is that if I write this code:</p> <pre><code>NSString* cacheControlString = [headers valueForKey:@"Cache-Control"]; cacheControlString = [headers valueForKey:@"Cache-Control"]; cacheControlString = [headers valueForKey:@"Cache-Control"]; cacheControlString = [headers valueForKey:@"Cache-Control"]; cacheControlString = [headers valueForKey:@"Cache-Control"]; cacheControlString = [headers valueForKey:@"Cache-Control"]; cacheControlString = [headers valueForKey:@"Cache-Control"]; </code></pre> <p>it always returns a correct value... Does someone had this kind of problem?! I am really going crazy!</p> <h2>Here is the full code:</h2> <pre><code>- (void) firstMethod { BOOL mustRevalidate = [self checkCacheControlElementForElement:@"must-revalidate" inHeaders:[response headers]]; BOOL publicResponse = [self checkCacheControlElementForElement:@"public" inHeaders:[response headers]]; BOOL privateResponse = [self checkCacheControlElementForElement:@"private" inHeaders:[response headers]]; } - (BOOL) checkCacheControlElementForElement:(NSString*)element inHeaders:(NSDictionary*)headers { NSString* cacheControlString = [headers valueForKey:@"Cache-Control"]; return [self checkCacheControlElementForElement:element inHeader:cacheControlString]; } - (BOOL) checkCacheControlElementForElement:(NSString*)element inHeader:(NSString*)headerString { if (!headerString) return NO; Header* header = [[Header alloc] initWithName:@"Cache-Control" andValue:headerString]; for (HeaderElement* headerElement in [header elements]) { if ([[headerElement name] isEqualToString:element]) { [header release]; return YES; } } [header release]; return NO; } </code></pre> <p>Header and HeaderElement are classes creates by me which help for working with headers, but that work just with the passed NSString objects. What checkCacheControlElementForElement:inHeader: method does is just to search if in a header there is a element.</p> <p>I have seen that, if I remove the second row to the method checkCacheControlElementForElement:inHeaders: letting it to return simply YES I have not the problem... but WHY? Header and HeaderElement classes does not work with the dictionary!</p> <p>As you can see nobody changes the 'headers' dictionary and you can be sure that values inside the dictionary are not autoreleased while I am working with it...</p>
 

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