StackOverflow2013

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POHow to pass NSData as NSString and get it back?
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copied!<p>i have a NSData object. </p> <p><strong>I want to convert it to a string, pass to a function and then reconvert back to NSData object.</strong></p> <p>But How?</p> <p>I tried this method, but NSData value it's different from the original!</p> <p>here my code:</p> <pre><code> // a generic class APClass *c = [[APClass alloc] init]; c.aNumber = 123; c.aString = @"my string"; // my data obj NSMutableData *data = [NSMutableData data]; // archiver to store class in nsdata NSKeyedArchiver *encoder = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data]; [encoder encodeObject:[NSNumber numberWithInt:c.aNumber] forKey:@"aNum"]; [encoder encodeObject:c.aString forKey:@"aStr"]; [encoder finishEncoding]; [encoder release]; [c release]; NSLog(@"%@", data); NSString *d = [NSString stringWithFormat:@"%@", data]; // --- NSString *strFromData = [NSString stringWithFormat:@"%@", d]; NSData *dataNM = [strFromData dataUsingEncoding:NSUTF8StringEncoding]; // decoder to retrieve class from nsdata NSKeyedUnarchiver *decoder = [[NSKeyedUnarchiver alloc] initForReadingWithData:dataNM]; int number = [[decoder decodeObjectForKey:@"aNum"] intValue]; NSString *string = [decoder decodeObjectForKey:@"aStr"]; [decoder finishDecoding]; [decoder release]; NSLog(@"[Number: %d] -- [String: %@]", number, string); </code></pre> <p>How can i convert back to original NSData? </p> <p>data and dataNM are different in size. Compiler give back this error:</p> <blockquote> <p>2012-04-02 16:33:28.269 DataTest[18008:f803] -[__NSCFData objectForKey:]: unrecognized selector sent to instance 0x6b46c80</p> <p>2012-04-02 16:33:28.270 DataTest[18008:f803] <em>*</em> Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFData objectForKey:]: unrecognized selector sent to instance 0x6b46c80'</p> </blockquote> <p>thanks.</p>

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