A very neat and highly underused feature of Kotlin is infix notations. After stumbling upon in it randomly, it’s become one of my favourite features.
Infix functions are:
- incredibly easy to learn
- quick to write/migrate
- write unbelievable syntax when paired with Extension function
What are infix expressions ?
Consider a function being called:
fun Long.add(number: Long) {
return this + number
}
val num = 10
val newnum = num.add(5)
Adding infix function at the start — we can call it like:
infix fun Long.add(number: Long) {
return this + number
}
val num = 10
val newnum = num add 5
instanceOf func is an example of a built in expression
Writing your own infix expression
Infix keyword works only for functions that have one parameter
Let’s take a function to reverse a string , isRevInfix uses the same function but in an infix syntax and magical to read !
There can be many other intuitive examples !!
a doesNotHaveAnAppointmentOn “Sunday”
a endsWith “a”
a beginsWith “c”
a hasSubString “d”
a isContainedIn “personList”
date isBetween Pair<startDate(),endDate()>
and the list goes on …
Cases where you can really see infix makes a difference in your code
- complex business logic with multiple if cases are unavoidable e.g.)
- isA/hasA relationShip
- makes leetcoding a lot more fun e.g) a isALeafNodeOf binaryTree
