Problem
Code Duplication
Maintainability
Solution
Find repeated patterns (not repeated code).
Create an abstraction.
Parametrize abstraction calls.
Use composition and avoid inheritance.
Unit test the new abstraction.
Sample Code
Wrong
class WordProcessor(var text: String = "") {
fun replaceText(patternToFind: String, textToReplace: String) {
text = "<<< ${text.replace(patternToFind, textToReplace} >>>"
}
}
class Obfuscator(var text: String = "") {
fun obfuscate(patternToFind: String, textToReplace: String) {
text = text.lowercase().replace(patternToFind, textToReplace)
}
}
Right
class TextReplacer {
fun replace(
patternToFind: String,
textToReplace: String,
subject: String,
replaceFunction: (String, String, String) -> String,
postProcessClosure: (String) -> String
): String =
replaceFunction(patternToFind, textToReplace, subject)
.let(postProcessClosure)
}
class WordProcessor(private var text: String = "") {
fun replaceText(patternToFind: String, textToReplace: String) {
text = TextReplacer()
.replace(
patternToFind,
textToReplace,
text,
replaceFunction = { pattern, replace, subject ->
subject.replace(pattern, replace)
},
postProcessClosure = { "<<< $it >>>" }
)
}
}
class Obfuscator(private var text: String = "") {
fun obfuscate(patternToFind: String, textToReplace: String) {
text = TextReplacer()
.replace(
patternToFind,
textToReplace,
text,
replaceFunction = { pattern, replace, subject ->
subject.replace(pattern, replace, ignoreCase = true)
},
postProcessClosure = { it.lowercase() }
)
}
}
Conclusion
Repeated code is always a smell. Copying and pasting code is always a shame. With our refactoring tools, we need to accept the challenge of removing duplication and trust our tests as a safety net.
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