i want to use when expression in this kind of situation ```w

Question

i want to use when expression in this kind of situation ```when string null gt this length gt 1 gt else gt ``` i resorted to this ```when this==null gt this length gt 1 gt else gt ``` is this idiomatic solution

menegatti · Answer

btw you can escape your code with 3 backticks ``` to make it look better

zucen.co · Answer

ok I will from now slightly smiling face

andyb · Answer

```when this is Nothing gt this length gt 1 gt else gt ``` Is the action of an empty String the same as a null If so you could rewrite it as ```when this is Nothing || this length == 0 gt else gt ```

zucen.co · Answer

ah no this is not a probem I was more wondering if I may call attrbute on the argument when arg in what i symbolicaly wrote as this length

andyb · Answer

Think I misunderstood the question unfortunately `this` will not correspond to the subject of the `when` condition To need to evaluate the branches using the name of the object outside the `when` block Hope that makes sense

zucen.co · Answer

Ah really aha think is I was using this construct in special context ``` fun String shortened maxLen Int=60 = when this == null gt this length lt maxLen gt this else gt $ this substring 0 maxLen +$ this length maxLen ``` so I thought this was in this context reference to when argument but in fact it is this as extended target

andyb · Answer

That s right

zucen.co · Answer

So is the way I worte it good way

andyb · Answer

that should be fine I d just compare it to Nothing rather than null though

zucen.co · Answer

aha I will look in dept at Nothing it is a bit new concept for me that Any vs Nothing and Nothing vs void slightly smiling face

andyb · Answer

You might find this blog post from < natpryce> helpful

zucen.co · Answer

Thanks Andy

Andreas Sinz · Answer

< andyb> how do you compare it to Nothing

andyb · Answer

this is Nothing

Andreas Sinz · Answer

but Nothing can be `Nothing` pun not intended

Andreas Sinz · Answer

`null is Nothing` results in `false`

andyb · Answer

``` val test String = null when test is Nothing gt println I am Nothing else gt println I am $test ``` This code prints out I am Nothing

andyb · Answer

Interestingly this code is different amp prints out I am null which indicates that it has gone into the `else` condition val test String = null when test is Nothing gt println I am Nothing else gt println I populated $test

andyb · Answer

That has really caught me out amp it looks like it might be a bug

zucen.co · Answer

PLS slightly smiling face when you find out if you will put it here smile

zucen.co · Answer

But one more difference this compiles ```val alfa String =null when alfa == null gt print nothing alfa length gt 1 gt print $ alfa length else gt print else ``` this does not ``` when alfa is Nothing gt print nothing alfa length gt 1 gt print $ alfa length else gt print else ```

Andreas Sinz · Answer

< andyb> `test is Nothing == false` is a bug