檔案會儲存在 Cloud Storage 值區中。這個值區中的檔案會以階層結構呈現,就像本機硬碟上的檔案系統,或是 Firebase Realtime Database 中的資料。 建立檔案的參照後,應用程式就能存取該檔案。然後,您可以使用這些參照上傳或下載資料、取得或更新中繼資料,或刪除檔案。參照可以指向特定檔案,也可以指向階層中的較高層級節點。
如果您使用過 Firebase Realtime Database,應該會覺得這些路徑非常熟悉。不過,檔案資料會儲存在 Cloud Storage 中,不會儲存在 Realtime Database 中。
可建立參照
建立參照,以上傳、下載或刪除檔案,或取得/更新檔案的中繼資料。您可以將參照視為指向雲端檔案的指標。參照是輕量級的,因此您可以視需要建立多個參照。此外,這些函式也可重複用於多項作業。
參考資料是使用 FirebaseStorage
服務建立,並呼叫其 reference
方法。
// 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()
// 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];
您可以在現有參照上使用 child
方法,建立樹狀結構中較低位置 (例如 'images/space.jpg'
) 的參照。
// 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)
// 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"];
使用參照瀏覽
您也可以使用 parent
和 root
方法,在檔案階層中向上導覽。parent
會向上導覽一層,root
則會導覽至最上層。
// 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()
// 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
和 root
可以多次串連,因為每個都會傳回參照。但 parent
的 root
例外狀況為 nil
。
// 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()
// 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];
參考屬性
您可以使用 fullPath
、name
和 bucket
屬性檢查參照,進一步瞭解參照指向的檔案。這些屬性會取得檔案的完整路徑、名稱和 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;
參考資料限制
參照路徑和名稱可包含按任何順序排列的有效 Unicode 字元,但須遵守特定限制,包括:
- 以 UTF-8 編碼時,reference.fullPath 的總長度必須介於 1 到 1024 個位元組之間。
- 不得使用回車或換行字元。
- 請避免使用
#
、[
、]
、*
或?
,因為這些符號無法與 Firebase Realtime Database 或 gsutil 等其他工具搭配使用。
完整範例
// 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()
// 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];
接著,我們將瞭解如何將檔案上傳至 Cloud Storage。