What do I do?
- Software engineer at Toast
- Mostly Android
- Originally Java, increasingly using Kotlin
3 things I like about Kotlin
- 1) Handling nulls
- 2) Functional collection methods
- 3) Extension functions
Some features I used when converting from Java
1) Null views in Android
view?.displayInvalidCardErrorMessage()if (view != null) {
view.hideProgressSpinner();
}Kotlin:
Java:
- Cases in Android where we must check the view is not null
- Kotlin makes this
- more succinct + readable
- forces null checks when type is nullable
2) Functional collections methods
- Refactored from Java -> Kotlin
- FluentIterable
- Kotlin collections methods
Functional collections methods
fun Check.getFirstOpenCreditCardPayment(): Optional<Payment> {
return Optional.fromNullable(payments.firstOrNull { payment ->
payment.paymentType == Payment.Type.CREDIT &&
!payment.isDeleted &&
payment.paymentStatus == Status.OPEN })
}private Predicate<Payment> isOpenCreditCard = payment -> {
return payment.paymentType == Payment.Type.CREDIT
&& !payment.isDeleted()
&& payment.paymentStatus == Status.OPEN;
};
private Optional<Payment> filterPayments(Check check, Predicate condition) {
Optional<ToastPosOrderPayment> result = FluentIterable.from(check.payments)
.filter(condition)
.first();
return result;
}
public Optional<Payment> getFirstOpenCreditCardPayment(Check check){
return filterPayments(check, isOpenCreditCard);
}FluentIterable:
Kotlin built in collections methods:
3) Extension Functions
- Write new functions for a class without altering or extending it
fun CardReaderService.canTakeEmvPayment(): Boolean {
return (canTakeQuickChipPayment() || canTakeFullEmvPayment())
} deck
By Nasreen Hunaina
