Hey I have object of `Event` I want to combine all property

Question

Hey I have object of `Event` I want to combine all property value into single string I did this without any problem I want to know is there any better way to optimise this code in memory efficiency etc SingleEventString kt ``` fun main var newString String = null val eventList = createData eventList forEachIndexed index event gt val title = event title val status = event status if title isNullOrEmpty newString = if index == 0 $title else $newString $title if status isNullOrEmpty newString = $newString $status println newString data class Event val title String = null val status String = null fun createData = listOf Event text 1 abc Event text 2 abc Event text 3 abc Event text 4 abc Event abc Event null abc ```

Sam · Answer

You could use a for this either on its own or via

Luke · Answer

To add to that you could use `eventList fold StringBuilder builder event gt toString `

Vivek Modi · Answer

what is builder and event

Luke · Answer

builder would be the StringBuilder and event would be each event one after the other But I am just realizing that what you want is even simpler `eventList joinToString separator = event gt ` This maps each event to a string and concats them with a space separator

Vivek Modi · Answer

That s great I ll try on my side

Vivek Modi · Answer

< Luke> I tried this code ```fun main var newString String = null val eventList = createData eventList joinToString separator = event gt val title = event title val status = event status if title isNullOrEmpty newString = $newString $title if status isNullOrEmpty newString = $newString $status newString toString println newString ``` and getting this `null text 1 abc text 2 abc text 3 abc text 4 abc abc abc` How to remove null in this

Luke · Answer

```val newString = eventList joinToString separator = event gt when title isNullOrEmpty gt status orEmpty status isNullOrEmpty gt title else gt $title $status ```

Vivek Modi · Answer

Sorry can you please explain me what is going on this 1 ```event title isNullOrEmpty gt event status orEmpty ``` 2 ```event status isNullOrEmpty gt event title``` why 1st one have `orEmpty ` and 2nd don t

Vivek Modi · Answer

< Luke> point up 2

Luke · Answer

1 If the title is null or is the empty string you return the status If the status is null you return the empty string 2 Since we already checked that the title is neither null or empty then calling orEmpty here is redundant

Luke · Answer

Another solution which you might find easier to understand is this

Luke · Answer

```val newString = createData asSequence flatMap sequenceOf it title it status filterNotNull filterNot it isEmpty joinToString separator = ```

Luke · Answer

Basically create an iteration of every title and status filter out nulls and empty strings and concatenate with space separator

Vivek Modi · Answer

Ok now this is great example I can easily understand that one Thanks a million

Vivek Modi · Answer

And above solution is working fine

nkiesel · Answer

you cold also replace ` filterNotNull filterNot it isEmpty ` with ` filterNot it isNullorEmpty `

Vivek Modi · Answer

Sure thanks

ephemient · Answer

```createData flatMap listOfNotNull it title ifEmpty null it status ifEmpty null joinToString separator = ```

Vivek Modi · Answer

< ephemient> thank you so much Can you please explain me what is difference between `flatMap` and `Map` Thanks

ephemient · Answer

` flatMap ` behaves like ` map flatten `

nkiesel · Answer

listOfNotNull returns a list containing 0 1 or 2 elements in your concrete example for every item returned from createData Therefore a map would return a list of these lists flatMap as just explained flattens this to a simple list by concatenating all the inner lists ```listOf Data t1 null Data null s2 Data t3 s3 map listOfNotNull it title ifEmpty null it status ifEmpty null t1 s2 t3 s3 listOf Data t1 null Data null s2 Data t3 s3 flatMap listOfNotNull it title ifEmpty null it status ifEmpty null t1 s2 t3 s3 ```

Vivek Modi · Answer

great explanation Thank you so much guys < nkiesel> < ephemient>