Các dữ liệu chức năng (int) cho phép các phần mềm ứng dụng để đọc dữ liệu của mảng. Chức năng này là quá tin tưởng, nó giả định rằng chỉ số được cung cấp trong phạm vi dữ liệu. Điều gì sẽ xảy ra nếu chỉ số không? Các dữ liệu chức năng (int, int) thậm chí còn tồi tệ hơn bởi vì nó ghi đè lên một địa điểm không rõ. | 380 Part VI The Part of Tens_ class Array public Array int s size 0 pData new int s if pData size s Array delete pData size 0 pData 0 either return or set the array data int data int index return pData index int data int index int newValue int oldValue pData index pData index newValue return oldValue protected int size int pData The function data int allows the application software to read data out of Array. This function is too trusting it assumes that the index provided is within the data range. What if the index is not The function data int int is even worse because it overwrites an unknown location. What s needed is a check to make sure that the index is in range. In the following only the data int function is shown for brevity int data unsigned int index if index size throw ExceptionCArray index out of range return pData index Chapter 29 Ten Ways to Avoid Adding Buns to Your Program 381 Now an out-of-range index will be caught by the check. Making index unsigned precludes the necessity of adding a check for negative index values. Commenting Your Code While You Write It You can avoid errors if you comment your code as you write it rather than waiting until everything works and then go back and add comments. I can understand not taking the time to write voluminous headers and function descriptions until later but you always have time to add short comments while writing the code. Short comments should be enlightening. If they re not they aren t worth much. You need all the enlightenment you can get while you re trying to make your program work. When you look at a piece of code you wrote a few days ago comments that are short descriptive and to the point can make a dramatic contribution to helping you figure out exactly what it was you were trying to do. In addition consistent code indentation and naming conventions make the code easier to understand. It s all very nice when the code is easy to read .
