How to access a field's value via reflection (Scala 2.8)
Solution 1
As others have mentioned, the reflection methods return Object
so you have to cast. You may be better using the method that the Scala compiler creates for field access rather than having to change the visibility of the private field. (I'm not even sure if the name private field is guaranteed to be the same as that of the accessor methods.)
val foo = new Foo
val method = foo.getClass.getDeclaredMethod("name")
val value = method.get(foo).asInstanceOf[String]
Solution 2
getDeclaredField
is a method of java.lang.Class
.
You have to change foo.getDeclaredField("name")
to foo.getClass.getDeclaredField("name")
(or classOf[Foo].getDeclaredField("name")
) to get the field.
You can get the type with getType
method in class Field
but it won't help you because it returns Class[_]
. Given than you know that the type is a String you can always cast the value returned using field.get(foo).asInstanceOf[String]
Solution 3
AFAIK, reflection always work with Object, and you have to cast the results yourself.
soc
Updated on June 03, 2022Comments
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soc almost 2 years
Consider the following code:
class Foo(var name: String = "bar")
Now i try to get the value and the correct type of it via reflection:
val foo = new Foo val field = foo.getClass.getDeclaredField("name") field.setAccessible(true) //This is where it doesn't work val value = field.get(????)
I tried things like field.get(foo), but that just returns an java.lang.Object but no String. Basically I need the correct type, because I want to invoke a method on it (e. g. toCharArray).
What is the suggested way to do that?
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gerferra about 14 yearsYes, I had misunderstood the question, now I have changed mi answer.
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soc about 14 yearsI fixed the missing getClass, this was only an oversight. I wonder how to do the cast without knowing what it is beforehand. If I knew everything about the class I have to handle i wouldn't need reflection... Thanks for the suggestions!
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gerferra about 14 yearsYou can pattern match the object with something like
value match { case s: String => /* do something with a string */ case _ => /* do something else */ }
. Don't know if I understand what you want to do. -
Evhz over 6 yearsworking well with foo.getClass.getDeclaredField("name") because foo.getClass.getDeclaredMethod does not have a member called get