装箱与拆箱的概念

        //经过数字类型建立数字对象(装箱)

        NSNumber *num1 = [[NSNumber alloc] initWithInteger:123];

        NSLog(@"%@", num1);

        NSNumber *num2 = [[NSNumber alloc] initWithDouble:12.3];

        NSLog(@"%@", num2);

        

        NSNumber *num3 = [NSNumber numberWithInt:34];

        NSLog(@"%@", num3);

        

        NSArray *arr1 = [NSArray arrayWithObjects:@"one", num1, nil];

        NSLog(@"%@", arr1);

        

        //数字对象转换为基本数字类型(拆箱)

        NSInteger value1 = [num1 integerValue];

        NSLog(@"value = %ld", value1);