Hi It would be nice that extension functions such us `inline

Question

Hi It would be nice that extension functions such us `inline fun lt T gt T takeUnless` would work lazily and short circuit code execution if condition is true kind of lazy evaluation of `previous expression` What s your thoughts Is it possible at all

gildor · Answer

what should be done lazy I m not sure how is that possible for such function

gildor · Answer

T already there and it must be returned immidiately

gildor · Answer

because predicate requires T it cannot be lazy

gildor · Answer

but you can write own extension that doesn t require eager receiver and just have additional lambda that computes lazily

gildor · Answer

But it will not be takeUnless anymore semantically

Pavlo Liapota · Answer

I am not sure what do you mean by gt kind of lazy evaluation of `previous expression` `takeUnless` returns `null` if condition is `true` But I guess what you want is just ```if condition null else foo ``` Soo `foo ` is evaluated only if condition is `false` And of course you can create extension function with a condition as a receiver if it makes sense for you

Antanas A. · Answer

yeah after closer inspection I ve noticed that `takeUnless` passes a value into predicate function

Antanas A. · Answer

and I until today I ve used it as if condition null else codeblock replacement

Antanas A. · Answer

I ve replaced it with extension function as suggested ` fun lt T gt takeUnless predicate Boolean block gt T T = if predicate block else null`

Antanas A. · Answer

at first I just thought if it s inline fun then it will be inlined in code and will wrap somehow expression variable on which it was called

Antanas A. · Answer

my case is ``` val event = GeneratedEvent on = true timestamp = randomize randomSeed max visibleRange start interval start RandomizationRange interval start totalVehicleMiles = dutyEvent totalVehicleMiles takeUnless interval start == visibleRange start ```

Antanas A. · Answer

as this code was written before and the special condition just emerged after requirements change

Antanas A. · Answer

so writing takeUnless on the end looked as fastest solution slightly smiling face

gildor · Answer

why not just ```val event = if interval start = visibleRange start GeneratedEvent else null ```

gildor · Answer

takeUnless without receiver looks really strange

Antanas A. · Answer

actually in production code there is a listOf filterNotNull

Antanas A. · Answer

yes I ve misused takeUnless I d haven t thought that its predicate function receives value as argument and used as just kind of generic convert to null if any expression is true

Antanas A. · Answer

will change my behaviour from now slightly smiling face

Antanas A. · Answer

thanks

Dico · Answer

I used to declare an extension function like Boolean ifTrue Which works like also but only if it s true just not a fan of the name