在 Apple 平台上創建 Cloud Storage 引用

您的文件存儲在Cloud Storage 存儲分區中。此存儲桶中的文件以分層結構呈現，就像本地硬盤上的文件系統或 Firebase 實時數據庫中的數據一樣。通過創建對文件的引用，您的應用程序可以訪問它。然後，這些引用可用於上傳或下載數據、獲取或更新元數據或刪除文件。引用可以指向特定文件或層次結構中的更高級別節點。

如果您使用過Firebase 實時數據庫，這些路徑對您來說應該非常熟悉。但是，您的文件數據存儲在 Cloud Storage 中，而不是實時數據庫中。

創建參考

創建引用以上傳、下載或刪除文件，或者獲取或更新其元數據。可以將引用視為指向雲中文件的指針。引用是輕量級的，因此您可以根據需要創建任意數量的引用。它們也可重複用於多個操作。

引用是使用FirebaseStorage服務創建的並調用其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];
    

您可以通過對現有引用使用child方法來創建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

您還可以使用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可以多次鏈接在一起，因為每個都返回一個引用。例外是root的parent級，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理解它們指向的文件。這些屬性獲取文件的完整路徑、名稱和存儲桶。

// 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的 Unicode 字符序列，但有一些限制，包括：

1. UTF-8 編碼時，reference.fullPath 的總長度必須在 1 到 1024 個字節之間。
2. 沒有回車或換行字符。
3. 避免使用# 、 [ 、 ] 、 *或? ，因為這些不能很好地與Firebase 實時數據庫或gsutil等其他工具配合使用。

完整示例

// 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，讓我們學習如何將文件上傳到 Cloud Storage。