I had successfully save a list with these blocks below.
My problem is I want to check whether the user’s already in one of the chatroom, so the list will not create a new one.
Example, if Person A is there in the index0 room, then function only read the data without create a new one.
You might be able to learn how to search through Firebase nodes from this topic:
If you get stuck, post a screenshot of what you’ve tried (the screenshot above is a Save block which doesn’t have anything to do with reading values from a list…).
Finally, I tried a different to do it. I use Firebase UID to separate each room and also use list viewer to show the chat. Is much easier for me . Probably there are more advance way to make this.
I shared my blocks and firebase DB here. Feel free to give some advice.
. Probably there are more advance way to make this.
Feel free to give some advice. 
