How do I retrieve specific data from firebase realtime database using flutter?

Question

I am building an application that is supposed to create a movie library for you. I have set up my firebase database to store the movie title and all the movie specifications inside the database like so:

The next step I want to take is reading only the movie titles (Official Secrets, Seberg, Unbreakable Kimmy Schmidt) to make a list displaying the movie titles to the user. I tried using

void readData()
  {
    DBRef.once().then((DataSnapshot datasnapshot){
      print('DATA SNAPSHOT NEXT LINE');
      print(datasnapshot.value);
    });
  }

But grabs all the data inside my firebase database when I only want the titles. How do I grab only the titles? Then following that, if a user selects a title I then want to go into the database and grab all the information that falls under that title. For example:

User has those 3 movies in their library
User Selects Seberg
Now my app goes into the database and grabs all the information contained under Seberg.

I have also tried:

  void readData()
  {
    DBRef.child('Official Secrets                 (2019)').once().then((DataSnapshot datasnapshot)
    {
      print('DATA SNAPSHOT NEXT LINE');
      print(datasnapshot.value);
    });
  }

I used this to try to test to grab only the title of the movie, but this returns null.

burakozyurt · Accepted Answer · 2020-05-06 01:28:32Z

1

You have to do something like this. But your data structure are not good

 List<String> readData()
  {
    List<String> titleList = new List()
    Map<String,String> map = new Map();
    DBRef.once().then((DataSnapshot datasnapshot){
      print('DATA SNAPSHOT NEXT LINE');
      print(datasnapshot.value);
      map = datasnapshot.value();
      map.forEach((key,value){
      map.add(key);
      continue;
      })
    });
    return titleList;
 }

answered May 6, 2020 at 1:28

burakozyurt

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Comments

Ashutosh Singh · Accepted Answer · 2020-05-05 20:52:35Z

Unfortunately, the simple answer is you can't. Not with the current schema. Due to the way data is organized in RTDB, it's not possible to fetch only the movie title without fetching the child data of the entire node.

What you'd have to do right now is called data flattening i.e avoid deep nesting to avoid fetching the entire data of the node. This guide on structuring data might help.

You can create an additional node called movie_titles and keep all your movie titles there and keep the reel-house node as it is.

Now, you always fetch the movie_titles node initially without getting all the data and show the titles in your app. When the user taps a particular title in your app, then fetch the corresponding data from the reel-house node.

Your DB might look somewhat like this

movie_titles:[
    "title 1",
    "title 2",
    "title 3",
    "title 4",    
],

reel-house: [
    "title 1": {
        // data for title 1
    },
    "title 2": {
        // data for title 2
    },
    "title 3": {
        // data for title 3
    },
    "title 4": {
        // data for title 4
    },
],

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