Scala Retrieve aggregate pattern inside flat map - scala

Question

I have this scenario when trying to aggregate the result of few methods .
What im trying to do is im getting a Future of an object that contain a list of objects .
Then im flat mapping the future to a list of strings
and then i would like to iterate this list
Than invoke couple of methods if it possible in a async way and then merge the result to one object i have to wait that all method will finish
and send the result to a database.
This is where i stuck ....
UPDATE
I edit the method as suggested in the comments now i getting type mismatch error
expected List[postMd.PostMD]....
,
def getComplatePost(url: String): Unit = {
val postMd = new PostMetaData
val com = new Comments
val post = new Post
val fullPost = new CompletePost
val postMdList: Future[List[postMd.PostMD]] = postMd.getPostMetaData(url, "396697410351933") // get the list of id
postMdList.flatMap(x => {
val fromid = x.map(_.fromID) //extract the Future to a list of string
for {
id <- fromid
val c = com.getComments(id)
val p = post.getPost(id)
}yield (c,p)
})
}
thanks
miki

Answer 1

You can use a 'for - yield' this case. 'for' executes the yield operation after each of its statement completes.
This mainly hold as, 'for' is a syntactic sugar which further gets mapped to nested flatMap or map or foreach ... depending on the operations being performed.
Below is a modified snippet from your code:
for {
id <- fromid
//invoke methods
c = com.getComments(id)
p = post.getPost(id)
k = post.getPostLikes(id)
} // merge results and send data to DB