using NSString + stringWithContentsOfFile:usedEncoding:error:

I've got problem with use + stringWithContentsOfFile:usedEncoding:error:

My problem in usedEncoding:(NSStringEncoding *)enc I don't know how can i set pointer to encoding. If i make it - programm is fail.

For example, in similar function we have encoding:(NSStringEncoding)enc - without pointer!

I want loading file开发者_如何学Python (file has encoding ISOLatin1) in NSString and use NSString as UTF8String.

how can i make it ?

thanks.

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NSStringEncoding encoding;
NSError* error;
NSString* myString = [NSString stringWithContentsOfFile:myFilePath usedEncoding:&encoding error:&error];