Scala flatMap over getConstructors method (reflection) -

i'm trying iterate on constructors of given class using reflection. problem need each element , return ones matches predicate. following code throws exception

classof[string].getconstructors.flatmap(x=> dosomething(x); if(predicate(x)) some(x) else none) 

the exception:

argument expression's type not compatible formal parameter type;  found   : java.lang.reflect.constructor[_] => iterable[java.lang.reflect.constructor[?0(in value $anonfun)]] forsome { type ?0(in value $anonfun) }  required: java.lang.reflect.constructor[_] => scala.collection.gentraversableonce[?b] 

i'm not sure if can done comprehension because need call on each element(not ones holds predicate):

for{     x <- c.getconsturctors     //dosomething(x) ??      if predicate(x) }yield{     //dosomething(x) - ones holds predicate     x } 

calling c.getmethods works i'm guessing has return type(array[methods] vs array[constructor[_]])...?

answer :

flatmap - alexey romanov answer

for comprehension(with of pamu):

for{     x <- c.getconsturctors     _ = dosomething(x)     if predicate(x) }yield x 

due details of type inference implementation, scala ends iterable[java.lang.reflect.constructor[a]] forsome { type } want iterable[java.lang.reflect.constructor[a] forsome { type }] (or shorter, iterable[java.lang.reflect.constructor[_]]). annotating type should work:

c.getconstructors.flatmap { x =>   dosomething(x)   (if (predicate(x)) some(x) else none): option[constructor[_]] } 

but must admit don't see why problem arises.