Re: Java8 ContainingType::methodName references

For a method without parameter, it becomes:

(_: Person).firstname

or

_.firstname

Sébastien

On Thu, Mar 3, 2016 at 11:26 PM, <[email protected]> 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?
>>>
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