Get a list of related items within a Firebase array that correspond to an item on the original list

I'm having trouble retrieving a list of items from Firebase, where each item contains a list of related items. I've attempted to use both firebase-util and the firebase array $extend feature without success.

The structure of my Firebase data is as follows:

items
    item1
        name: "Item 1"
        user: user1
        images
           image1: true
           image2: true
    item2
        name: "Item 2"
        user: user1
        images:
            image3: true
            image4: true
    item3
        name: "Item 3"
        user: user2
        images:
            image5: true
            image6: true

users
    user1
        name: "User 1"
        email: "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="27525442551667424a464e4b0944484a">[email protected]</a>"
    user2
        name: "User 2"
        email: "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="dfaaacbaaded9fbab2beb6b3f1bcb0b2">[email protected]</a>"

images
    image1
        image: "data:image/jpeg;base64,/9j/..."
        thumb: "data:image/jpeg;base64,/9j/..."
    image2
        image: "data:image/jpeg;base64,/9j/..."
        thumb: "data:image/jpeg;base64,/9j/..."
    image3
        image: "data:image/jpeg;base64,/9j/..."
        thumb: "data:image/jpeg;base64,/9j/..."
    image4
        image: "data:image/jpeg;base64,/9j/..."
        thumb: "data:image/jpeg;base64,/9j/..."
    image5
        image: "data:image/jpeg;base64,/9j/..."
        thumb: "data:image/jpeg;base64,/9j/..."

My goal is to retrieve a list of items with all associated data structured like this:

items
    item1
        name: "Item 1"
        user
            name: "User 1"
            email: "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="bbcec8dec98afbded6dad2d795d8d4d6">[email protected]</a>"
        images
            image1
                image: "data:image/jpeg;base64,/9j/..."
                thumb: "data:image/jpeg;base64,/9j/..."
            image2
                image: "data:image/jpeg;base64,/9j/..."
                thumb: "data:image/jpeg;base64,/9j/..."
    item2
        name: "Item 2"
        user
            name: "User 1"
            email: "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="cabfb9afb8fb8aafa7aba3a6e4a9a5a7">[email protected]</a>"
        images
            image3
                image: "data:image/jpeg;base64,/9j/..."
                thumb: "data:image/jpeg;base64,/9j/..."
            image4
                image: "data:image/jpeg;base64,/9j/..."
                thumb: "data:image/jpeg;base64,/9j/..."
    item3
        name: "Item 3"
        user
            name: "User 2"
            email: "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="73060016014133161e121a1f5d101c1e">[email protected]</a>"
        images
            image5
                image: "data:image/jpeg;base64,/9j/..."
                thumb: "data:image/jpeg;base64,/9j/...    
            image6
                image: "data:image/jpeg;base64,/9j/..."
                thumb: "data:image/jpeg;base64,/9j/..."

While this seems like a common scenario, I am facing challenges in implementing it. I have explored a solution similar to this but without any success due to the nested nature of the lists.

javascriptangularjsfirebaseangularfirefirebase-util

Answer №1

The goal is to display a list of items along with their corresponding images.

Each item in the list should initially show one image as a thumbnail.

Here is a recommended approach:

To populate the list of items and their initial thumbnails, we should have a separate node from which we can retrieve the setup information.

Updated items node

items:
  item_id_xx: //Firebase will generate this unique node name
   name: "Item 2"
   user: "uid_for_user_1"
   images:
     image3: "data:image/jpeg;base64,/9j/..."
     image4: "data:image/jpeg;base64,/9j/..."

Below is the structure for the main list where users can click on a thumbnail to view more details:

item_list_for_ui
  random_node_0
    item_id: "item_id_aa"
    name: "Item 1"
    initial_thumb: "data:image/jpeg;base64,/9j/..."
    link_to: "image1"
  random_node_1
    item_id: "item_id_xx"
    name: "Item 2"
    initial_thumb: "data:image/jpeg;base64,/9j/..."
    link_to: "image3"
  random_node_2
    item_id: "item_id_qq"
    name: "Item 3"
    initial_thumb: "data:image/jpeg;base64,/9j/..."
    link_to: "image1"

When the application launches, populate the list using the items_list_for_ui node.

This node is shallow and includes the Firebase item_id, the item name (if necessary), the link for the initial image thumbnail, and the main image link in Firebase.

For instance, if a user clicks on the thumbnail for Item 2, the item details can be loaded by using observeSingleEvent with .value at

/items/item_id_xx/images/image3

You can enhance this structure by adding a rollover link to the item_list_for_ui

  random_node_1
    item_id: "item_id_xx"
    name: "Item 2"
    initial_thumb: "data:image/jpeg;base64,/9j/..."
    thumb_link: "image3"
    rollover_thumb: "external link to rollover"
    rollover_link: "image4"

This setup offers flexibility as you can easily interchange thumbnails and rollovers in the main list by updating the respective child nodes.

It's also efficient because it prevents loading excessive items and their associated image nodes, which could overwhelm the user interface in some cases.

With this design, the item_list_for_ui remains concise even with a large number of items, making it a manageable subset of the data.

You might think that duplicating data is not ideal. However, in Firebase, duplicating data is normal and beneficial as it maintains a flatter structure and improves query performance.

For further reading, check out Denormalizing Data Keeps Your Breath Minty Fresh

Answer №2

Shoutout to @Jay and @Eric for their invaluable input that contributed to my solution. I've incorporated elements from both of their suggestions to reach a resolution. Let me walk you through how I arrived at it.

Initially, I made adjustments to the schema by introducing a new key for the primary image of each item, labeled cover. However, in response to the original query, I opted to load all images. Here's how the updated items schema looks:

items
    item1
        name: "Item 1"
        user: user1
        cover: image1
        images
           image1: true
           image2: true
    item2
        name: "Item 2"
        user: user1
        cover: image3
        images:
            image3: true
            image4: true
    item3
        name: "Item 3"
        user: user2
        cover: image5
        images:
            image5: true
            image6: true

Next, this is the method I utilized to retrieve the aforementioned list (leveraging the async library). It might present a more efficient way to achieve the same outcome:

getItems: function(cb){
    var items = ref.child("items");
    items.on("value", function(snapshot){

        var item_length = snapshot.numChildren(),
            final_items = [],
            readed = 0;

        ref.child("items").on("child_added", function(item){

            var item_id = item.key(),
                itemData = item.val(),

                user = ref.child("users").child(itemData.user),
                cover = ref.child("images").child(itemData.cover),
                images = new Firebase.util.NormalizedCollection(
                       [ref.child("items").child(item_id).child("images"),'alertImages'],
                        ref.child('images')
                 ).select('images.image','images.thumb').ref();

                async.parallel([
                    function(callback){
                        user.on("value", function(user_snap){
                            callback(null, user_snap.val());
                        });
                    },
                    function(callback){
                        images.on("value", function(images_snap){
                            callback(null, images_snap.val());
                        });
                    },
                    function(callback){
                        cover.on("value", function(cover_snap){
                            callback(null, cover_snap.val());
                        });
                    }
                ], function(err, results){
                    if(!!err){
                        cb(err,null)
                    }else{
                        itemData.user = results[0];
                        itemData.images = results[1];
                        itemData.cover = results[2];

                        final_items.push(itemData);
                        readed += 1;
                        if(readed === item_length){
                            cb(null,final_items);
                        }
                    }
               });
        });
    });
}

As a result, the output will resemble the following structure:

item1
    name: "Item 1"
    cover:
        image: "data:image/jpeg;base64,/9j/..."
        thumb: "data:image/jpeg;base64,/9j/..."
    user
        name: "User 1"
        email: "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="52272137206312373f333b3e7c313d3f">[email protected]</a>"
    images
        image1
            image: "data:image/jpeg;base64,/9j/..."
            thumb: "data:image/jpeg;base64,/9j/..."
        image2
            image: "data:image/jpeg;base64,/9j/..."
            thumb: "data:image/jpeg;base64,/9j/..."
item2
    name: "Item 2"
    cover:
        image: "data:image/jpeg;base64,/9j/..."
        thumb: "data:image/jpeg;base64,/9j/..."
    user
        name: "User 1"
        email: "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="e792948295d6a7828a868e8bc984888a">[email protected]</a>"
    images
        image3
            image: "data:image/jpeg;base64,/9j/..."
            thumb: "data:image/jpeg;base64,/9j/..."
        image4
            image: "data:image/jpeg;base64,/9j/..."
            thumb: "data:image/jpeg;base64,/9j/..."
item3
    name: "Item 3"
    cover:
        image: "data:image/jpeg;base64,/9j/..."
        thumb: "data:image/jpeg;base64,/9j/..."
    user
        name: "User 2"
        email: "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="e396908691d1a3868e828a8fcd808c8e">[email protected]</a>"
    images
        image5
            image: "data:image/jpeg;base64,/9j/..."
            thumb: "data:image/jpeg;base64,/9j/..."
        image6
            image: "data:image/jpeg;base64,/9j/..."
            thumb: "data:image/jpeg;base64,/9j/..."

Answer №3

If you have a wealth of data at your disposal, you can iterate through your image collection and utilize their metadata as unique identifiers throughout the database.

var itemsArray = [];
    for(var index in items) {
        var currentItem = items[index];
        var imageList = [];
        for(var imgIndex in currentItem.images) {
            imageList.push(currentItem.images[imgIndex]);
        }
        itemsArray.push({
            name: currentItem.name,
            user: users[currentItem.user],
            images: imageList
        });
    }

This process will generate an array of objects structured like this:

{
    name: "Item 1",
    user: {
        name: "User 1",
        email: "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="afdafdccd99eeaced2ded6c381cdcec0c2">[email protected]</a>"
    },
    images: [{
            image: "data:image/jpeg;base64,/9j/..."
            thumb: "data:image/jpeg;base64,/9j/..."
        },{
            image: "data:image/jpeg;base64,/9j/..."
            thumb: "data:image/jpeg;base64,/9j/..."
    }]
}

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