Kotlin: Prefer clarity over conciseness

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K otlin provide us a lot of handy utilities, like takeIf etc. It could help make code so much concise, removed temporary variable etc.

However, if we get too much into it, it complicates the readability of the code.

Take for example the below.

savedStateHandle.get<String>(KEY).takeIf {
!it.isNullOrEmpty()
}?.let { setValue(it) } ?: removeValue()

One doing this might feel great as it

• eliminates if-else,
• chain the code together,
• eliminate temporary variable.

However the down side of this code is,

1. It would takes a some time for one to understand the flow of the code. It obscure the simple logic behind the code.
2. If we decompile the code, look at the number of temporary variable it generates.

Object var2 = this.savedStateHandle.get("Key");
boolean var3 = false;
boolean var4 = false;
String it = (String)var2;
int var6 = false;
CharSequence var7 = (CharSequence)it;
boolean var8 = false;
boolean var9 = false;
String var10000 = (String)(var7 != null && var7.length() != 0 ? var2 : null);
if (var10000 != null) {
   String var10 = var10000;
   var3 = false;
   var4 = false;
   var6 = false;
   Intrinsics.checkExpressionValueIsNotNull(var10, "it");
   this.setValue(var10);
} else {
   this.removeValue();
}

The simplified version

Let’s get back to it’s old Java way of writing, simple IF-ELSE. Doesn’t look that elegant, but one look, everything is understood.

val savedMessage = savedStateHandle.get<String>(KEY)
if (savedMessage.isNullOrBlank()) {
    removeValue()
} else {
    setValue(savedMessage)
}

Beside if we decompile, it looks neat too, with only little generated variables.

String savedMessage = (String)this.savedStateHandle.get("Key");
CharSequence var3 = (CharSequence)savedMessage;
boolean var4 = false;
boolean var5 = false;
if (var3 == null || StringsKt.isBlank(var3)) {
   this.removeValue();
} else {
   this.setValue(savedMessage);
}

Using When

Of course, if we like, we could improve it a little with when , shorten it by one line compare with IF-ELSE

val savedMessage = savedStateHandle.get<String>(KEY)
when {
    savedMessage.isNullOrBlank() -> removeValue()
    else -> setValue(savedMessage)
}

The decompiled code looks good too.

String savedMessage = (String)this.savedStateHandle.get("Key");
CharSequence var3 = (CharSequence)savedMessage;
boolean var4 = false;
boolean var5 = false;
if (var3 == null || StringsKt.isBlank(var3)) {
   this.removeValue();
} else {
   this.setValue(savedMessage);
}

Using run

But if one complaint we need to code the temporary variable savedMessage , we could eliminate it using run (or some other Scope function). Like below…

savedStateHandle.get<String?>(KEY).run {
when {
        this.isNullOrBlank() -> removeValue()
        else -> setValue(this)
    }
}

The decompile code looks like below. Not as nice, but it’s still better than the first one.

Object var2 = this.savedStateHandle.get("Key");
boolean var3 = false;
boolean var4 = false;
String $this$run = (String)var2;
int var6 = false;
CharSequence var7 = (CharSequence)$this$run;
boolean var8 = false;
boolean var9 = false;
if (var7 == null || StringsKt.isBlank(var7)) {
   this.removeValue();
} else {
   this.setValue($this$run);
}