[NSConcreteValue floatValue]: unrecognized selector sent to instance

Question

In my project I have this problem.

I have a NSDictionary, when I try to call a value sometimes the app crash and Xcode give me this error:

• [NSConcreteValue floatValue]: unrecognized selector sent to instance

Here is the code to call the value of the dictionary (The value isn't nil):

    float valueTest = [[change valueForKey:@"new"] floatValue];

EDIT

This is the structure of my NSDictionary:

 {
    kind = 1;
    new = "0.02696711";
    old = "0.04064206";
}

The dictionary is never equal to nil

The method is this:

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
}

The dictionary is created by the system. I check with logs the content of the dictionary and it's already correct and already the same format.

I don't have other information.

I'm searching for a method to prevent the crash.

Sorry for possible english errors

Thanks

Answer 1

Okay, it appears we are trying to observe the ISO property of an AVCaptureDevice. And it appears that sometimes it arrives as an NSValue that is not typed as an NSNumber. I don't know why that is, but you can check with this condition:

strcmp(@encode(float), [[change valueForKey:@"new"] objCType]) == 0

If that passes, you can just extract the value directly:

float f;
[[change valueForKey:@"new"] getValue:&f];