Your files are stored in a Cloud Storage bucket. The files in this bucket are presented in a hierarchical structure, just like the file system on your local hard disk, 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, get or update metadata or delete the file. A reference can either point to a specific file or to a higher level node in the hierarchy.
If you've used the Firebase Realtime Database , these paths should seem very familiar to you. However, your file data is stored in Cloud Storage , notin the Realtime Database .
Create a Reference
Create a reference to upload, download, or delete a file, or to get 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.
References are created using the FirebaseStorage
service and calling its reference
method.
Swift
// Get a reference to the storage service using the default Firebase App let storage = Storage . storage () // Create a storage reference from our storage service let storageRef = storage . reference ()
Objective-C
// Get a reference to the storage service using the default Firebase App FIRStorage * storage = [ FIRStorage storage ]; // Create a storage reference from our storage service FIRStorageReference * storageRef = [ storage reference ];
You can create a reference to a location lower in the tree,
say 'images/space.jpg'
, by using the child
method on an existing reference.
Swift
// Create a child reference // imagesRef now points to "images " let imagesRef = storageRef . child ( " images " ) // Child references can also take paths delimited by '/ ' // spaceRef now points to "images/space.jpg " // imagesRef still points to "images " var spaceRef = storageRef . child ( " images / space . jpg " ) // This is equivalent to creating the full reference let storagePath = " \ ( your_firebase_storage_bucket ) / images / space . jpg " spaceRef = storage . reference ( forURL : storagePath )
Objective-C
// Create a child reference // imagesRef now points to "images " FIRStorageReference * imagesRef = [ storageRef child : @ " images " ]; // Child references can also take paths delimited by '/ ' // spaceRef now points to "images/space.jpg " // imagesRef still points to "images " FIRStorageReference * spaceRef = [ storageRef child : @ " images / space . jpg " ]; // This is equivalent to creating the full reference spaceRef = [ storage referenceForURL : @ " gs : //<your-firebase-storage-bucket>/images/space.jpg"];
Navigate with References
You can also use the parent
and root
methods to navigate up in our
file hierarchy. parent
navigates up one level,
while root
navigates all the way to the top.
Swift
// Parent allows us to move to the parent of a reference // imagesRef now points to 'images ' let imagesRef = spaceRef . parent () // Root allows us to move all the way back to the top of our bucket // rootRef now points to the root let rootRef = spaceRef . root ()
Objective-C
// Parent allows us to move to the parent of a reference // imagesRef now points to 'images ' imagesRef = [ spaceRef parent ]; // Root allows us to move all the way back to the top of our bucket // rootRef now points to the root FIRStorageReference * rootRef = [ spaceRef root ];
child
, parent
, and root
can be chained together multiple times, as
each returns a reference. The exception is the parent
of root
, which
is nil
.
Swift
// References can be chained together multiple times // earthRef points to "images/earth.jpg " let earthRef = spaceRef . parent ()?. child ( " earth . jpg " ) // nilRef is nil, since the parent of root is nil let nilRef = spaceRef . root (). parent ()
Objective-C
// References can be chained together multiple times // earthRef points to "images/earth.jpg " FIRStorageReference * earthRef = [[ spaceRef parent ] child : @ " earth . jpg " ]; // nilRef is nil, since the parent of root is nil FIRStorageReference * nilRef = [[ spaceRef root ] parent ];
Reference Properties
You can inspect references to better understand the files they point to
using the fullPath
, name
, and bucket
properties. These properties
get the file's full path, name, and bucket.
Swift
// Reference's path is: "images/space.jpg " // This is analogous to a file path on disk 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 bucket is the name of the storage bucket where files are stored spaceRef . bucket
Objective-C
// Reference's path is: "images/space.jpg " // This is analogous to a file path on disk 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 bucket is the name of the storage bucket where files are stored spaceRef . bucket ;
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 Carriage Return or Line Feed characters.
- Avoid using
#,[,],*, or?, as these do not work well with other tools such as the Firebase Realtime Database or gsutil .
Full Example
Swift
// Points to the root reference let storageRef = Storage . storage (). reference () // Points to "images " let imagesRef = storageRef . child ( " images " ) // Points to "images/space.jpg " // Note that you can use variables to create child values let fileName = " space . jpg " let spaceRef = imagesRef . child ( fileName ) // File path is "images/space.jpg " let path = spaceRef . fullPath // File name is "space.jpg " let name = spaceRef . name // Points to "images " let images = spaceRef . parent ()
Objective-C
// Points to the root reference FIRStorageReference * storageRef = [[ FIRStorage storage ] reference ]; // Points to "images " FIRStorageReference * imagesRef = [ storageRef child : @ " images " ]; // Points to "images/space.jpg " // Note that you can use variables to create child values NSString * fileName = @ " space . jpg " ; FIRStorageReference * spaceRef = [ imagesRef child : fileName ]; // File path is "images/space.jpg " NSString * path = spaceRef . fullPath ; // File name is "space.jpg " NSString * name = spaceRef . name ; // Points to "images " imagesRef = [ spaceRef parent ];
Next, let's learn how to upload files to Cloud Storage .
