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kotlinlang

If I have a collection and i want to chain `.filter` only if a certain condition is true, how do I do that? ```.apply { if (boolean) filter {} }``` does not seem to work

You need else condition, just add `else this`

Oh, and also you should replace `apply` with `run`

Apply doesn't return result of the lamda and used only to modify/use rexeicer

if you want call site to be easy to read, just go with an extension function

```inline fun &lt;T&gt; Iterable&lt;T&gt;.filterIf( applyFilter : Boolean, predicate: (T) -&gt; Boolean ) : List&lt;T&gt; =
        if( applyFilter ) filter( predicate ) else toList()```

for more custom support, you could even change the Boolean into a lambda that returns a boolean

though the call site usage would then involve two lambdas within ()