Kotlin Code Smell 32 - Repeated Code
Breaking the Chains of Duplication for Elegant and Maintainable Code
I've started to work as a software engineer at 2014, however, I started to write code at high-school.
My first language was Assembly, but still, I fall in love with the possibilities to make the computer to do as you wish, shortly after that I started to write in C.
Later on I studied a practical engineering in electricity, and during this time discovered that I preferred much more writing code than design electrical components.
As a result of this understanding I decided to switch and study bachelor degree in computer science in Reichman university, where the focus was of the Java language.
Today I'm working at SumUp using Kotlin, SpringBoot & Micronaut, Cassandra and Kafka
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.
