Re: Java8 ContainingType::methodName references

As far as I can see Java doesn't make it possible either to reflect on 
method references to get the method name. (
http://stackoverflow.com/questions/19845213/how-to-get-the-methodinfo-of-a-java-8-method-reference
)
I think you can use the same trick as they do in Java if you really want to 
do this: 
http://benjiweber.co.uk/blog/2013/12/28/typesafe-database-interaction-with-java-8/

Best,
Jasper

Op vrijdag 4 maart 2016 23:46:18 UTC+1 schreef [email protected]:
>
> 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]> 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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>>>>
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>>
>>

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