The Evils of Copy and Paste

1
The Evils of Copy and Paste

• Presented by
• Daniel Daugherty
• Daniel_cfug_at_danield.us

2
Why is Copy and Paste Evil?

• Wait a second I use copy and paste all the time
  what is wrong with it??????
• You mean I have to retype everything every time??

3
Why is Copy and Paste Evil?

• Copy and Paste ! Code Reuse
• Copy and Paste is code duplication
• But more is good right?

4
What should I do instead?

• Cut and Paste is your friend.
• Cut the code and place where it can be referenced
  in two or more places (actual code reuse).
• This may require some refactoring of the code
  into a more reusable segment of code.

5
Advantages Of Cut and Paste

• No duplication of code
• No duplication of bug(s) within duplicated code.
• Improved Readability
• Improved Maintainability
• Improved Testability

6
Code Reuse options in ColdFusion

• variables
• include
• module
• custom tags
• import

• CFC
• Functions
• Web Services
• AJAX

7
Does it matter how much I copy and paste?

• Copying as little as one word could be a reason
  to extract that into a reusable segment. Even
  simple text labels.
• Examples
• Externalize a field label or column header
• If length(x) and isdate(x)
• If length(y) and isdate(y) becomes
• If validDate(x) If validDate(y)

8
Copy Paste Change?

• But I just need to copy paste this 3 lines and
  make two small changes.
• Small changes can be very error prone. Large
  changes tend to be tested better than small.
• Possible options for reuse of this code.
• CFModule/Custom Tag
• CFC/Function

9
What about other languages?

• JavaScript, ActionScript - methods, variables,
  external files, prototypes.
• CSS - named classes , multiple selectors for one
  set of attribute(s). Breaking style up into
  smaller re-useable blocks Layout, Text, Color
• Java - classes, methods, variables, JSP tags,
  EJB, web services,

10
What about other applications?

• Are both applications for same customer/company/cl
  ient?
• Use web services to make the logic available to
  both applications.
• If both live on the same servers use
  mappings/custom tag paths to allow both apps to
  reference the same code.

11
Code Example/Walkthrough
12
Wrap Up

• Try keeping track of how many times you copy and
  paste code for one day. You might be surprised
  at how often you do it.
• Then think each time you do how can I move this
  to a reusable format.
• Some copy paste is OK.
• Questions?