//NSNumber
    //int类型转化为对象
    int i=10;
    NSNumber *n1=[NSNumber numberWithInt:i];
    NSLog(@"%@",n1);
    //float类型转化为对象
    float f=1.3;
    NSNumber *n2=[NSNumber numberWithFloat:f];
    NSLog(@"%@",n2);
    
    //对象转回int型
    int i1=[n1 intValue];
    //对象转回float型
    float f1=[n2 floatValue];