学步园

http://yul100887.blog.163.com/blog/static/200336135201321455832/

用NSValue包装:
typedef struct {
    float real;
    float imaginary;
} ImaginaryNumber;

ImaginaryNumber miNumber;
miNumber.real = 1.1;
miNumber.imaginary = 1.41;

NSValue *miValue = [NSValue value: &miNumber
                            withObjCType:@encode(ImaginaryNumber)];

ImaginaryNumber miNumber2;
[miValue getValue:&miNumber2];