I m a little confused Intellij offers me to sometimes change kotlinlang #getting-started

I'm a little confused. Intellij offers me to sometimes change lambdas to references. Is that using reflection? and isn't it bad practice to use reflection as it incurs performance loss (as i've heard)?

Francesc

05/21/2023, 5:11 AM

However, function references also implement function types and can be used as function literals. Such usages are not considered "real" reflection and introduce no performance overhead compared to lambda expressions

https://kt.academy/article/fk-function-references

ephemient

05/21/2023, 5:14 AM

when inlined, there is no difference at runtime between a lambda and a function reference

when not inlined, there is a minor difference as the function reference is more specialized

Any::toString.name // "toString"
{ it: Any -> it.toString() }.name // does not compile

Any::toString == Any::toString // true
{ it: Any -> it.toString() } == { it: Any -> it.toString() } // false

but it still does not involve runtime reflection

note that invoking

toString()

on a lambda or callable reference will cause kotlin-reflect to load metadata which can be slow: https://youtrack.jetbrains.com/issue/KT-54175

05/21/2023, 5:44 AM

Thank you both for the detailed answers. Adding on to the main question: is the same also true for a property reference? ex:

instance::foo.get()
instance::foo.set("bar")

ephemient

05/21/2023, 6:09 AM

similar, when inline it's the same as a lambda (e.g.

"".let(String::length)

), otherwise it involves some machinery that doesn't directly involve runtime reflection or metadata but might access that depending on what calls are made

get and set are fine

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