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  • e

    Eugenio

    10/06/2015, 2:49 PM
    might also be nice to have some kind of switch to enable some faster caching in case the app in question make heavy use of reflection
  • d

    desseim

    10/06/2015, 4:06 PM
    hum I still fail to see how to declare a fully parameterized java class instance without an instance reference @apatrida ?
  • a

    apatrida

    10/06/2015, 4:10 PM
    You cannot create a fully parameterized java class instance in any language on the JVM. you can create a Class<T> or a Type. Of Type there are 5 implementations. You are looking for Type not Class.
  • a

    apatrida

    10/06/2015, 4:10 PM
    so use reified generics to create a Type
  • a

    apatrida

    10/06/2015, 4:10 PM
    or give me a use case (mocked up method) of what you were trying to do
  • a

    apatrida

    10/06/2015, 4:11 PM
    if you don't know about Type vs. Class, that's something you need to understand first.
  • d

    desseim

    10/06/2015, 4:13 PM
    nah OK, I’ll try with types I thought they’d be a syntax close to the java one.
  • v

    vmironov

    10/06/2015, 4:21 PM
    Is there any way to check if generic parameter is nullable? Basically, I want to be able to write something like:
    Copy code
    public inline fun <reified V : View?> View.find(id: Int): V {
  val result = findViewById(id)

  if (result == null && !V::class.isNullable) {
    throw IllegalArgumentException("Unable to find view ${view.resources.getResourceName(id)}")
  }

  return result as V
}
  • v

    vmironov

    10/06/2015, 4:21 PM
    Copy code
    // optional, returns null
val optional = view.find<View?>(some_invalid_id)

// required, throws an exception
val required = view.find<View>(some_invalid_id)
  • a

    apatrida

    10/06/2015, 4:31 PM
    the 
    Ktype
    should have isNullable or isOptional, check it
  • a

    apatrida

    10/06/2015, 4:31 PM
    Kotlin reflection returns objects that tell you nullability, optional, etc.
  • a

    apatrida

    10/06/2015, 4:31 PM
    back later, production issue.
  • v

    vmironov

    10/06/2015, 4:41 PM
    @apatrida: you mean 
    V::class.defaultType.isMarkedNullable
    ? Looks like it always returns 
    false
  • u

    udalov

    10/06/2015, 4:51 PM
    I'm afraid there's no API currently for that, so not possible unless you want to dig into the internals of Kotlin reflection
  • v

    vmironov

    10/06/2015, 4:55 PM
    @udalov: that’s sad. Do you have any plans on exposing such API?
  • u

    udalov

    10/06/2015, 4:55 PM
    yes, of course
  • a

    apatrida

    10/06/2015, 4:57 PM
    I'm not sure how you would say "is a class nullable" when it is a reference to a class that might be. the type of the variable or the parameter to a method could be nullable but a class? doesn't make sense to ask that question. Is String nullable? no, but 
    val s: String?
    means 
    s
    is, but String still is just a class
  • u

    udalov

    10/06/2015, 4:58 PM
    oh I thought @vmironov meant to check if the type parameter's bound is nullable, I see now that is not the case
  • d

    desseim

    10/06/2015, 5:00 PM
    Still, I can get 
    Class
    instance which the compiler treats as of type 
    Class<List<String>>
    from an instance (e.g. 
    listOf<String>().javaClass
    ), isn’t there really a way to do the same without instantiating an object ?
  • a

    apatrida

    10/06/2015, 5:00 PM
    how Guillaume?
  • a

    apatrida

    10/06/2015, 5:01 PM
    given mechanics of the VM how?
  • a

    apatrida

    10/06/2015, 5:01 PM
    only the COMPILER can see the generics, or the runtime can see the generics of a SUPER ClASS or INTERFACE
  • u

    udalov

    10/06/2015, 5:01 PM
    @desseim: 
    List::class.java as Class<List<String>>
  • d

    desseim

    10/06/2015, 5:01 PM
    yeah, I’m only wanting the compiler to
  • a

    apatrida

    10/06/2015, 5:02 PM
    then 
    fullType<List<String>>().type
  • a

    apatrida

    10/06/2015, 5:02 PM
    which is above in this channel
  • a

    apatrida

    10/06/2015, 5:02 PM
    and it will not be a 
    Class<T>
    it will be a 
    Type
    or specifically a 
    ParameterizedType
  • a

    apatrida

    10/06/2015, 5:03 PM
    see my note on reading up on 
    Class
    vs 
    Type
  • a

    apatrida

    10/06/2015, 5:03 PM
    because you can never have a class that has it's own generic info, it doesn't exist. It is one of the implementations of 
    Type
    that has that
  • a

    apatrida

    10/06/2015, 5:03 PM
    so if you confuse the two, you will never find the true answer.
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