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Editorial Team
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Asked: 2026-06-03T13:51:24+00:00

I have a strange problem (strange if you ask me). Im using a NSNumber

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I have a strange problem (strange if you ask me). Im using a NSNumber object to store a number (doh). When I try to “modify” it it crashes my application. The code I’m using looks like this:

if ([frequency intValue] > 19999)
    return;
frequency = [NSNumber numberWithInt:([frequency intValue] + 1)]; //I think this line is causing me the problem
[freqLabel setText:[NSString stringWithFormat:@"%i Hz", [frequency intValue]]];

Where is frequency the NSNumber and freqLabel my label to which I write the value every time this gets called.
Why is this incorrect? It works when I call it for the first time. Is it that NSNumber numberWithInt always returns a new object which I’m trying to assign to frequency?
How do I fix this? Whats the correct way to change a NSNumber‘s value?

Sorry for my bad english (if there are any mistakes).

EDIT:
The error log looks like this:

[__NSCFType intValue]: unrecognized selector sent to instance 0x73430e0
2012-05-09 16:39:28.064 MyApp[31939:10703] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFType intValue]: unrecognized selector sent to instance 0x73430e0'
*** First throw call stack:
(0x17a6022 0x28afcd6 0x17a7cbd 0x170ced0 0x170ccb2 0x4821 0x17a7e99 0x49d14e 0x49d0e6 0x543ade 0x543fa7 0x543266 0x4c23c0 0x4c25e6 0x4a8dc4 0x49c634 0x2e49ef5 0x177a195 0x16deff2 0x16dd8da 0x16dcd84 0x16dcc9b 0x2e487d8 0x2e4888a 0x49a626 0x1cca 0x1c15)
terminate called throwing an exception

But it doesn’t always show this error. Sometimes it causes an EXC_BAD_ACCESS. Should I store my variable in a temporary NSNumber?

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1 Answer

  1. Editorial Team

    You can’t just alloc/init something once and then you have a lifelong reference to that type. When you assign frequency to numberWithInt, then you are overwriting the previous alloc/init value with an autorelease value (which will be released later and cause the exact behavior you are describing). The reason it works with self.frequency is because your property is set as a retain property, so it automatically retains the autorelease value. Add a retain to your numberWithInt line and it will be fine (or do what you are doing now with self.frequency).

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