Create a Storage Reference on iOS

Your files are stored in a Firebase 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 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 Google Cloud Storage, not in 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 as 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 from the storage service on your Firebase app by calling the referenceForURL: method and passing in a URL of the form gs://<your-firebase-storage-bucket>. You can find this URL in the Storage section of the Firebase console.

// 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 referenceForURL:@"gs://<your-firebase-storage-bucket>"];
  

// Get a reference to the storage service, using the default Firebase App
let storage = FIRStorage.storage()

// Create a storage reference from our storage service
let storageRef = storage.referenceForURL("gs://<your-firebase-storage-bucket>")
    

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.

// 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
FIRStorageReference *spaceRef = [storage referenceForURL:@"gs://<your-firebase-storage-bucket>/images/space.jpg"];
  

// 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"
let spaceRef = storageRef.child("images/space.jpg")

// This is equivalent to creating the full reference
let 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.

// Parent allows us to move to the parent of a reference
// imagesRef now points to 'images'
FIRStorageReference *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];
  

// 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()
    

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.

// 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];
  

// References can be chained together multiple times
// earthRef points to "images/earth.jpg"
var earthRef = spaceRef.parent()?.child("earth.jpg")

// nilRef is nil, since the parent of root is nil
var 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.

// 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;
  

// 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:

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

Full Example

// Points to the root reference
FIRStorageReference *storageRef = [[FIRStorage storage] referenceForURL:@"gs://<your-bucket-name>"];

// 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"
FIRStorageReference *imagesRef = [spaceRef parent];
  

// Points to the root reference
let storageRef = FIRStorage.storage().referenceForURL("gs://<your-bucket-name>")

// 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 imagesRef = spaceRef.parent()
    

Next, let's learn how to upload files to Firebase Storage.