Getting 'nan' when inserting method in stringWithFormat

I have simplifed some methods for ease of understanding and correction of the error. I get a 'nan' instead of getting the number and don't understand why. I want to put the getNumber method inside the return开发者_StackOverflow社区 statement. When I have the method inside it returns a string of nan but when I just put the 26 inside it returns 26, what I want.

-(double) getNumber { return 26; }


-(NSString *) convertToString {
        return [NSMutableString stringWithFormat: @"%Lf",[self getNumber]];
// returns 'nan'           when I replace [self getNumber] with 15 I get 15
}

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You have a couple problems in your code.

1. Return a double, not an integer in getNumber. While automatic coercion will occur, write clean code.
2. Use the %g format specifier, not %Lf. %g is for doubles.

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You might want to use "%f" instead of "%Lf", since you are passing a double, not a long double

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It's your format specifier. You should use "%g" to format a double.