Trying to concatenate a firstName + middle + last name. Only including a space between the values if...

# getting-started

[Colton Idle]

Trying to concatenate a firstName + middle + last name. Only including a space between the values if they're not blank, and trying to not have double spaces between first and last if there is no middle name. Is there some std lib function for this? Or am I stuck doing a few if statements?

[Jordan Gout]

You could do something like that:

val firstname: String? = "John"
    val middlename: String? = " "
    val lastname: String? = null
    
    val names: String = listOf(firstname, middlename, lastname)
    .filter { !it.isNullOrBlank() } 
    .joinToString(" ")

[Adam S]

.joinToString(" ") { it.trim() }

[Adam S]

(Just in case - but hopefully (to be more defensive and consistent) the trim() happens earlier!)

[Jordan Gout]

Indeed trim is a good idea.
I would move it before filtering

listOf(...)
.map { it.trim() }
.filter { ... }
.joinToString(" ")

[Joffrey]

If the filtering is done with isNullOrBlank the trim doesn't need to be first. It avoids having one more operation since the map can be merged with joinToString

[Joffrey]

On a second note, thinking of names like this is technically wrong, unless your audience is very limited:
https://www.kalzumeus.com/2010/06/17/falsehoods-programmers-believe-about-names/

[Jordan Gout]

It avoids having one more operation since the map can be merged with joinToString

indeed 💯

[Colton Idle]

thanks. i knew about joinToString, but didn't think about just creating a temp list 😂

Thanks all

[CLOVIS]

No need to instantiate a list before filtering:

listOfNotNull(firstName, middleName, lastName)
    .joinToString(" ")

[Joffrey]

This doesn't filter out the empty/blank parts, though

[CLOVIS]

Ah, I'm assuming they're null when missing.

[Joffrey]

In the original example, they aren't. But yeah it's probably generally better to design it that way. If it comes from a text field, a .takeIf { it.isNotBlank() } is a simple way of cleaning things up

[ephemient]

.ifBlank { null }

[Joffrey]

Oh, TIL

[Colton Idle]

FWIW, Ended up with

listOf(first, middle, last)
    .mapNotNull { it.trim().ifBlank { null } }
    .joinToString(" ")

[Colton Idle]

Also, I'm using ifBlank all the time now. nice convenience method

[CLOVIS]

There's also ifEmpty for collections

[Joffrey]

You should rarely need it within your code base, by the way, it should only be useful for cleaning input at the surface of your code. Throughout the code base, the data should be assumed "clean".