您的檔案會儲存在 Cloud Storage 值區中。這個值區中的檔案會以階層式結構呈現,如同本機硬碟中的檔案系統,或是 Firebase 即時資料庫中的資料。建立檔案的參照後,應用程式就能取得該檔案的存取權。這些參照便可用於上傳或下載資料、取得或更新中繼資料或刪除檔案。參照可以指向特定檔案,或是階層中更高層級的節點。
如果您已使用過 Firebase 即時資料庫,應該不太熟悉這些路徑。不過,檔案資料儲存在 Cloud Storage 中,而「不是」儲存在即時資料庫中。
可建立參照
建立參照以上傳、下載或刪除檔案,或是取得或更新其中繼資料。參照可以視為雲端中檔案的指標,參照簡單,因此您可以視需要建立任意數量的參照。這些作業也能重複用於多項作業。
參照是使用 FirebaseStorage
服務建立,並呼叫其 reference
方法。
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];
您可以使用現有參照的 child
方法,建立對樹狀結構中較低位置的參照 (例如 'images/space.jpg'
)。
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"];
使用參考資料進行導覽
您也可以使用 parent
和 root
方法向上瀏覽檔案階層。parent
會向上瀏覽一個層級,而 root
則會導覽至頂部。
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
和 root
可以多次鏈結,因為各自會傳回參照。例外狀況是 root
的 parent
,也就是 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];
參照屬性
您可以使用 fullPath
、name
和 bucket
屬性檢查參照,進一步瞭解指向的檔案。這些屬性會取得檔案的完整路徑、名稱和值區。
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;
參考檔案的限制
參照路徑和名稱可包含任何序列的有效 Unicode 字元,但系統會設下某些限制:
- 使用 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。
- 避免使用
#
、[
、]
、*
或?
,因為這些工具並不適合與 Firebase 即時資料庫或 gsutil 等其他工具搭配使用。
完整範例
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];
接下來,我們將說明如何上傳檔案至 Cloud Storage。