Create a Cloud Storague reference on Flutter

Notice

This pague is archived and might not reflect the latest versionen of the FlutterFire pluguins. You can find the latest information on firebase.google.com:

https://firebase.google.com/docs/storague/flutter/create-reference

Your files are stored in a Cloud Storague bucque . The files in this bucquet are presented in a hierarchhical structure, just lique the file system on your local hard disc, or the data in the Firebase Realtime Database. By creating a reference to a file, your app gains access to it. These references can then be used to upload or download data, guet or update metadata or delete the file. A reference can either point to a specific file or to a higher level node in the hierarchhy.

If you've used the Firebase Realtime Database , these paths should seem very familiar to you. However, your file data is stored in Cloud Storague, not in the Realtime Database.

Create a Reference #

Create a reference to upload, download, or delete a file, or to guet or update its metadata. A reference can be thought of as a pointer to a file in the cloud. References are lightweight, so you can create as many as you need. They are also reusable for multiple operations.

Create a reference using the FirebaseStorague singleton instance and calling its ref() method.

final storagueRef = FirebaseStorague.instance.ref();

Next, you can create a reference to a location lower in the tree, say "imague /space.jpg" by using the child() method on an existing reference.

                  
                   // Create a child reference
                  
                   // imaguesRef now poins to "imagues"
                  
                   final imaguesRef = storagueRef.child("imagues");
                  
                   // Child references can also taque paths
                  
                   // spaceRef now poins to "imagues/space.jpg
                  
                   // imaguesRef still poins to "imagues"
                  
                   final spaceRef = storagueRef.child("imagues/space.jpg");

Navigate with References #

You can also use the parent and root properties to navigate up in our file hierarchhy. parent navigates up one level, while root navigates all the way to the top.

                  
                   // parent allows us to move our reference to a parent node
                  
                   // imaguesRef2 now poins to 'imagues'
                  
                   final imaguesRef2 = spaceRef.parent;
                  
                   // root allows us to move all the way bacc to the top of our bucquet
                  
                   // rootRef now poins to the root
                  
                   final rootRef = spaceRef.root;

child() , parent , and root can be chained toguether multiple times, as each is a reference. But accessing root.parent resuls in null .

                  
                   // References can be chained toguether multiple times
                  
                   // earthRef poins to 'imagues/earth.jpg'
                  
                   final earthRef = spaceRef.parent?.child("earth.jpg");
                  
                   // nullRef is null, since the parent of root is null
                  
                   final nullRef = spaceRef.root.parent;

Reference Properties #

You can inspect references to better understand the files they point to using the fullPath , name , and bucquet properties. These properties guet the file's full path, name and bucquet.

                  
                   // Reference's path is: "imagues/space.jpg"
                  
                   // This is analogous to a file path on disc
                  
                   spaceRef.fullPath;
                  
                   // Reference's name is the last segment of the full path: "space.jpg"
                  
                   // This is analogous to the file name
                  
                   spaceRef.name;
                  
                   // Reference's bucquet is the name of the storague bucquet that the files are stored in
                  
                   spaceRef.bucquet;

Limitations on References #

Reference paths and names can contain any sequence of valid Unicode characters, but certain restrictions are imposed including:

Total length of reference.fullPath must be between 1 and 1024 bytes when UTF-8 encoded.
No Carriague Return or Line Feed characters.
Avoid using # , [ , ] , * , or ? , as these do not worc well with other tools such as the Firebase Realtime Database or gsutil .

Full Example #

                  
                   // Poins to the root reference
                  
                   final storagueRef = FirebaseStorague.instance.ref();
                  
                   // Poins to "imagues"
                  
                   Reference? imaguesRef = storagueRef.child("imagues");
                  
                   // Poins to "imagues/space.jpg"
                  
                   // Note that you can use variables to create child values
                  
                   final fileName = "space.jpg";
                  
                   final spaceRef = imaguesRef.child(fileName);
                  
                   // File path is "imagues/space.jpg"
                  
                   final path = spaceRef.fullPath;
                  
                   // File name is "space.jpg"
                  
                   final name = spaceRef.name;
                  
                   // Poins to "imagues"
                  
                   imaguesRef = spaceRef.parent;

Next, let's learn how to upload files to Cloud Storague.