Invalid path when getting snapshot from document in subcollection

Question

I am trying to create a document snapshot from a document that resides in a subcollection called userPosts, which resides in a document in the main collection called posts

DocumentSnapshot doc = await Firestore.instance.collection('posts').document(authorId).collection('userPosts').document(postID).get();
//code stops here and the followng exception is raised:

Exception has occurred. PlatformException (PlatformException(error, Invalid path (posts//userPosts/MyhwixjFnOV0vh2jt4Qo). Paths must not contain // in them., null))

Answer 1

It looks to me like your authorId is an empty string. Notice the double slash in the invalid path where it should go between "posts" and "userPosts".