Firebase retrieving related data in swift - swift

Question

I'm new to Firebase. Not good at DB also.
I'm really hoping that people could give me advices about my DB design and retrieving data codes.
I designed the DB as below.
The comment have a createTs for ordering.But the content shouldn't ordered by create time. So I put a "index" key into contents info in the post.(I'm not sure if it is a good way)
About the data retrieving, I made a dataManager object to load data.
DataManger.swift
func loadPosts(completeBlock : ([Post]) -> Void ) {
ref.child("posts").observeEventType(.Value , withBlock: { snapshot in
var postList : [Post] = []
if snapshot.value is NSNull {
} else {
for post in snapshot.children {
let postSnap = post as! FIRDataSnapshot
let post = Post()
post.setValue(withSanpShot: postSnap)
post.commentList = []
for key in post.comments.keys {
self.loadPostComment(withKey: key, completeBlock: { (comment) in
post.commentList.append(comment)
})
}
post.contentList = []
for key in post.contents.keys {
self.loadPostContent(withKey: key, completeBlock: { (content) in
post.contentList.append(content)
})
}
postList.append(post)
}
}
completeBlock(postList)
})
}
func loadPostComment(withKey key: String, completeBlock:(Comment) -> Void) {
ref.child("post-comments").child(key).observeEventType(.Value, withBlock: { commentSnapShot in
let comment = Comment()
comment.setValue(withSanpShot: commentSnapShot)
completeBlock(comment)
})
}
func loadPostContent(withKey key: String, completeBlock:(PostContent) -> Void) {
ref.child("post-contents").child(key).observeEventType(.Value, withBlock: { contentSnapShot in
let content = PostContent()
content.setValue(withSanpShot: contentSnapShot)
completeBlock(content)
})
}
And struct of the Post.swift.
class Post: NSObject {
var postID : String
var authorID: String
var title: String
var createTS : NSNumber
var comments : [String : AnyObject]
var contents : [String : AnyObject]
var commentList : [Comment] {
didSet {
//TODO: add some closure to update view.Maybe also need sorting codes
print("commentList : \(commentList)")
}
}
var contentList : [PostContent] {
didSet {
//TODO: add some closure to update view.Maybe also need sorting codes
print("contentList : \(contentList)")
}
}
}
I'm not sure the work I'v done is the right way to using it.Although I could got the data I want.
Please give me advices. That will be really helpful to me. Thanks.