Groovy Method References

I was listening to a podcast recently about Eclipse tooling for Java 8 and heard them talking about method references, and one of my co-workers mentioned it as a feature in Groovy. I recently ran across a problem which seemed particular well suited for this feature.

I had a list with different implementations of the Field class which each had a form of a get... method. For instance the ExternalDecimalAsInt has a getInt method, while the StringField has getString. method.  Both methods parse a byte stream and return the data. Since I'm writing Groovy, I don't care about the data type, I just wanted a simple way to invoke the get... method, regardless of the class type.

So I created a method reference in my object, and using a switch statement load the method reference according to the type of object that I'm dealing with.

class MyObject {
  def MethodClosure read //probably would omit the data type normally
} 

private void generateReader(MyObject myObject, Field field) {
  switch (field) {
    case StringField:
      myObject.read = field.&getString
      break
    case IntAccessor:
      myObject.read = field.&getInt
      break
    case BigDecimalAccessor:
      myObject.read = field.&getBigDecimal
      break
    case LongAccessor:
      myObject.read = field.&getLong
      break
    case BigIntegerAccessor:
      myObject.read = field.&getBigInteger
      break
  }
}

//invokes getString, getInt, etc... depending on the object type
def value = myObject.read(bytes) 

Of course, you can always do the same thing with closures, but there's a little less syntax with the method references, and it looks cooler. Once I can use Java 8, I hear that method references are also more efficient than lamba expressions, the equivalent to Groovy closures.

case StringField:
  myObject.read = { field.getString() }