Is there something more elegant instead of this snippet set

Question

Is there something more elegant instead of this snippet set to null and return the value that was before raise exception if it was null previously ```val previous = someField someField = null return previous```

Joffrey · Answer

I find this pretty clear like this honestly Although I would likely use ` error some meaningful message ` instead of ` ` If you really want an alternative you could do ```return someField also someField = null ``` But I m not sure it s more elegant

Richard Gomez · Answer

`requireNotNull someField Some meaningful message `is another option IMO it has a more clear intent than ` ` or ` error `

Karlo Lozovina · Answer

Wait so `return someField also someField = null ` will return the old value not the null that s been set inside the block

Joffrey · Answer

< Richard Gomez> It depends on whether this is a state error or an illegal argument What you suggested is for illegal arguments The equivalent of what you suggested for state errors would be `checkNotNull` Now whether to use `checkNotNull` or ` error ` depends on how you want the program to read I find both acceptable under certain circumstances

Joffrey · Answer

< Karlo Lozovina> yes `also` returns the value of its receiver So first `someField ` is evaluated and passed to `also` as receiver then `also` does its thing and then it returns whatever value was initially given to it

Richard Gomez · Answer

That s true I just caution against ` ` in general because `requireNotNull` `checkNotNull` or ` error ` result in clearer intent and error messages I tend to see ` ` used in two scenarios this can t be null trust me but the compiler isn t smart enough to determine this e g ` filter it = null ` I have no idea what I m doing and want these warnings to go away smile

Richard Gomez · Answer

< Karlo Lozovina> What Joffrey said if you re curious ` also ` compiles to something like ``` public String foo String var10000 = someField Intrinsics checkNotNull var10000 String var0 = var10000 int var2 = false I have no idea why this is here someField = String null return var0 ```

Joffrey · Answer

Sometimes there is stuff in the bytecode to keep the line numbers or for debugging purposes but I also have no idea why this particular extra variable is there slightly smiling face

Karlo Lozovina · Answer

thanks guys cleared a few things for me that ` also ` block was confusing at first it s getting late here slightly smiling face I m gonna go with ` ` it s basically something that should never happen so I m going for brevity sake

Karlo Lozovina · Answer

also block now reads kind of nice to me going with it instead of manually doing what the compiler would do anyway smile