PostsAdapter.kt

    override fun onBindViewHolder(postsViewHolder : ViewHolder, position: Int) {
        val post = posts[position]
        holder.title!!.text = post.title
        holder.description!!.text = post.description
        var hashtags = post.hashTags
        val sb = StringBuilder()
        hashtags.forEach { 
            sb.apply { 
                append(it)
                append(",")
            }
        }
        holder.hashtags.text = sb.toString()
    }