How do programmers practice code reuse

Question

I've been a bad programmer because I am doing a copy and paste. An example is that everytime i connect to a database and retrieve a recordset, I will copy the previous code and edit, copy the code that sets the datagridview and edit. I am aware of the phrase code reuse, but I have not actually used it. How can i utilize code reuse so that I don't have to copy and paste the database code and the datagridview code.,

Answer 1

The essence of code reuse is to take a common operation and parameterize it so it can accept a variety of inputs.

Take humble printf, for example. Imagine if you did not have printf, and only had write, or something similar:

//convert theInt to a string and write it out.
char c[24];
itoa(theInt, c, 10);
puts(c);

Now this sucks to have to write every time, and is actually kind of buggy. So some smart programmer decided he was tired of this and wrote a better function, that in one fell swoop print stuff to stdout.

printf("%d", theInt);

You don't need to get as fancy as printf with it's variadic arguments and format string. Even just a simple routine such as:

void print_int(int theInt)
{
    char c[24];
    itoa(theInt, c, 10);
    puts(c);
}

would do the trick nickely. This way, if you want to change print_int to always print to stderr you could update it to be:

void print_int(int theInt)
{
    fprintf(stderr, "%d", theInt);
}

and all your integers would now magically be printed to standard error.

You could even then bundle that function and others you write up into a library, which is just a collection of code you can load in to your program.

Following the practice of code reuse is why you even have a database to connect to: someone created some code to store records on disk, reworked it until it was usable by others, and decided to call it a database.

Libraries do not magically appear. They are created by programmers to make their lives easier and to allow them to work faster.

Answer 2

Put the code into a routine and call the routine whenever you want that code to be executed.