Re: Java8 ContainingType::methodName references

Ah, that would be a solution for the syntax.
The second part of the question is how to reflect on this function body to 
get the property name back as a string.

Example:
class Person {
  def age() = {
    Random.nextInt
  }
}

def getMethodName(property: Person => Int): String = {
    // How to reflect the property name itself out of the anonymous function
}

val property: Person => Int = (_: Person).age

println(getMethodName(property)) // should print "Person.age"

This that possible with Scala reflections?


On Thursday, March 3, 2016 at 11:35:00 PM UTC+1, Sébastien Doeraene wrote:
>
> For a method without parameter, it becomes:
>
> (_: Person).firstname
>
> or
>
> _.firstname
>
> Sébastien
>
> On Thu, Mar 3, 2016 at 11:26 PM, <[email protected] <javascript:>> wrote:
>
>> Hi, thank you for your reply.
>>
>> I just tried this:
>>
>> class Person {
>>   def firstname() = {
>>     "Scala"
>>   }
>> }
>>
>> val f: (Person, Person) => Int = _ firstname _
>> val g = (_: Person) firstname (_: Person)
>>
>>
>>
>> But this result in this compilation error:
>> Error:(9, 23) too many arguments for method firstname: ()String
>>   val g = (_: Person) firstname (_: Person)
>>                       ^
>> Error:(8, 38) too many arguments for method firstname: ()String
>>   val f: (Person, Person) => Int = _ firstname _
>>                                      ^
>>
>> Cheers,
>> Prag
>>
>>
>>
>> On Thursday, March 3, 2016 at 10:58:40 PM UTC+1, Sébastien Doeraene wrote:
>>>
>>> Hi,
>>>
>>> You can get what you want with:
>>>
>>> val f: (Person, Person) => Int = _ instanceMethodName _
>>>
>>> or, in the absence of an expected type helping the inference of the type 
>>> of _,
>>>
>>> val f = (_: Person) instanceMethodName (_: Person)
>>>
>>> Cheers,
>>> Sébastien
>>>
>>> On Thu, Mar 3, 2016 at 10:50 PM, <[email protected]> wrote:
>>>
>>>> Java 8 supports method references using the double colon :: operator.
>>>>
>>>> https://docs.oracle.com/javase/tutorial/java/javaOO/methodreferences.html
>>>>
>>>> There are four types of these:
>>>> -ContainingClass::staticMethodName (Reference to a static method)
>>>> -containingObject::instanceMethodName (Reference to an instance method 
>>>> of a particular object)
>>>> -ContainingType::methodName (Reference to an instance method of an 
>>>> arbitrary object of a particular type)
>>>> -ClassName::new (Reference to a constructor)
>>>>
>>>> In Scala, for example this one is supported: 
>>>> containingObject::instanceMethodName
>>>> by using:
>>>> containingObject.instanceMethodName _
>>>>
>>>> But what suprises me is that Scala doesn't seem to support 
>>>> ContainingType::methodName.
>>>> ContainingType::methodName can be handy when for example you need to 
>>>> dynamically create objects and perform reflections to call getter and 
>>>> setter method in a strong typed way. Which can be handy in UI code and 
>>>> object construction/binding code.
>>>>
>>>> Other languages also support this:
>>>> -Java: 
>>>> https://docs.oracle.com/javase/tutorial/java/javaOO/methodreferences.html
>>>> -Kotlin: https://kotlinlang.org/docs/reference/reflection.html
>>>> -Groovy: http://groovy-lang.org/metaprogramming.html (ExpandoMetaClass)
>>>> -C#: 
>>>> http://joelabrahamsson.com/getting-property-and-method-names-using-static-reflection-in-c/
>>>>
>>>> It would be nice if something like this would be possible in Scala:
>>>>   case class Person(name: String)
>>>>
>>>>   def getMethodName(....): String = {
>>>>     // ....
>>>>   }
>>>>   
>>>>   getMethodName(Person::name) // returns "name" or "Person.name"
>>>>
>>>>
>>>>
>>>> Am I missing something?
>>>>
>>>> -- 
>>>> You received this message because you are subscribed to the Google 
>>>> Groups "scala-language" group.
>>>> To unsubscribe from this group and stop receiving emails from it, send 
>>>> an email to [email protected].
>>>> For more options, visit https://groups.google.com/d/optout.
>>>>
>>>
>>> -- 
>> You received this message because you are subscribed to the Google Groups 
>> "scala-language" group.
>> To unsubscribe from this group and stop receiving emails from it, send an 
>> email to [email protected] <javascript:>.
>> For more options, visit https://groups.google.com/d/optout.
>>
>
>

-- 
You received this message because you are subscribed to the Google Groups "scala-language" group.
To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
For more options, visit https://groups.google.com/d/optout.