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 Firebase Realtime Database 中的資料一樣。建立檔案參照後,應用程式就能取得檔案存取權。這些參照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,也可以指向階層中較高層級的節點。
如果您曾使用 Firebase Realtime Database,這些路徑應該會讓您覺得很熟悉。不過,您的檔案資料會儲存在 Cloud Storage 中,而非 Realtime Database。
可建立參照
建立參照,以便上傳、下載或刪除檔案,或取得或更新檔案中繼資料。您可以將參照視為指向雲端檔案的指標。參照項目的大小較小,因此您可以視需要建立多個參照項目。這些函式也可用於多項作業。
您可以使用 FirebaseStorage
服務並呼叫其 reference
方法來建立參照。
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];
您可以在現有參照上使用 child
方法,建立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"];
使用參照導覽
您也可以使用 parent
和 root
方法,在檔案階層中向上瀏覽。parent
會向上一層瀏覽,而 root
會一直瀏覽至頂端。
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
可以連結多次,因為每個都會傳回參照。例外狀況是 root
的 parent
,即 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,以便進一步瞭解參照所指向的檔案。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;
參考資料限制
參照路徑和名稱可包含任何有效的 Unicode 字元序列,但有以下限制:
- 如果使用 UTF-8 編碼,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?
,因為這些工具無法與其他工具 (例如 Firebase Realtime Database 或 gsutil) 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。