在 Apple 平台上建立 Cloud Storage 參考

您的檔案儲存在Cloud Storage 儲存桶中。此儲存桶中的檔案以分層結構呈現，就像本機硬碟上的檔案系統或 Firebase 即時資料庫中的資料一樣。透過建立對文件的引用，您的應用程式可以存取它。然後，這些引用可用於上傳或下載資料、取得或更新元資料或刪除檔案。引用可以指向特定檔案或層次結構中的更高層級節點。

如果您使用過Firebase 即時資料庫，那麼您應該對這些路徑非常熟悉。但是，您的檔案資料儲存在 Cloud Storage 中，而不是儲存在即時資料庫中。

建立參考

建立引用以上傳、下載或刪除文件，或取得或更新其元資料。可以將引用視為指向雲端中檔案的指標。參考是輕量級的，因此您可以根據需要建立任意數量的參考。它們還可以重複用於多種操作。

引用是使用FirebaseStorage服務並呼叫其reference方法建立的。

// 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];
    

您可以透過對現有引用使用child方法來建立對樹中較低位置的引用，例如'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"
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"];
     

使用參考導航

您也可以使用parent和root方法在我們的文件層次結構中向上導航。 parent向上導航一級，而root一直導航到頂部。

// 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可以多次連結在一起，因為每個都回傳一個引用。 root的parent是個例外，它是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屬性檢查引用以更好地了解它們指向的檔案。這些屬性取得檔案的完整路徑、名稱和儲存桶。

// 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;
    

參考文獻的限制

引用路徑和名稱可以包含任何有效 Unicode 字元序列，但有某些限制，包括：

1. 當 UTF-8 編碼時，reference.fullPath 的總長度必須介於 1 到 1024 位元組之間。
2. 沒有回車或換行字元。
3. 避免使用# 、 [ 、 ] 、 *或? ，因為它們不能與其他工具（例如Firebase 即時資料庫或gsutil ）很好地配合使用。

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];
    

接下來，我們來學習如何將文件上傳到雲端儲存。