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
如要上傳或下載檔案、刪除檔案,或取得或更新中繼資料,您必須建立要操作檔案的參照。您可以將參照視為指向雲端檔案的指標。參照是輕量資源,因此您可以視需要建立多個參照,而且還可用於多個作業。
如要建立參照,請使用 getStorage()
取得 Storage 服務的執行個體,然後以服務做為引數呼叫 ref()
。這個參照會指向 Cloud Storage 儲存桶的根目錄。
Web
import { getStorage, ref } from "firebase/storage"; // Get a reference to the storage service, which is used to create references in your storage bucket const storage = getStorage(); // Create a storage reference from our storage service const storageRef = ref(storage);
Web
// Get a reference to the storage service, which is used to create references in your storage bucket var storage = firebase.storage(); // Create a storage reference from our storage service var storageRef = storage.ref();
您可以建立對樹狀結構中較低位置的參照,例如在呼叫 ref()
時,將這個路徑做為第二個引數傳入,以便建立 'images/space.jpg'
的參照。
Web
import { getStorage, ref } from "firebase/storage"; const storage = getStorage(); // Create a child reference const imagesRef = ref(storage, 'images'); // imagesRef now points to 'images' // Child references can also take paths delimited by '/' const spaceRef = ref(storage, 'images/space.jpg'); // spaceRef now points to "images/space.jpg" // imagesRef still points to "images"
Web
// Create a child reference var imagesRef = storageRef.child('images'); // imagesRef now points to 'images' // Child references can also take paths delimited by '/' var spaceRef = storageRef.child('images/space.jpg'); // spaceRef now points to "images/space.jpg" // imagesRef still points to "images"
使用參照導覽
您也可以使用 parent
和 root
屬性向上瀏覽檔案階層。parent
會向上一層瀏覽,而 root
會一直瀏覽至頂端。
Web
import { getStorage, ref } from "firebase/storage"; const storage = getStorage(); const spaceRef = ref(storage, 'images/space.jpg'); // Parent allows us to move to the parent of a reference const imagesRef = spaceRef.parent; // imagesRef now points to 'images' // Root allows us to move all the way back to the top of our bucket const rootRef = spaceRef.root; // rootRef now points to the root
Web
// Parent allows us to move to the parent of a reference var imagesRef = spaceRef.parent; // imagesRef now points to 'images' // Root allows us to move all the way back to the top of our bucket var rootRef = spaceRef.root; // rootRef now points to the 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 null
。
Web
import { getStorage, ref } from "firebase/storage"; const storage = getStorage(); const spaceRef = ref(storage, 'images/space.jpg'); // References can be chained together multiple times const earthRef = ref(spaceRef.parent, 'earth.jpg'); // earthRef points to 'images/earth.jpg' // nullRef is null, since the parent of root is null const nullRef = spaceRef.root.parent;
Web
// References can be chained together multiple times var earthRef = spaceRef.parent.child('earth.jpg'); // earthRef points to 'images/earth.jpg' // nullRef is null, since the parent of root is null var nullRef = 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、檔案名稱,以及檔案儲存的值區。
Web
import { getStorage, ref } from "firebase/storage"; const storage = getStorage(); const spaceRef = ref(storage, 'images/space.jpg'); // 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;
Web
// 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:
- 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?
,因為這些工具無法與其他工具 (例如 Firebase Realtime Database 或 gsutil) 搭配使用。
完整範例
Web
import { getStorage, ref } from "firebase/storage"; const storage = getStorage(); // Points to the root reference const storageRef = ref(storage); // Points to 'images' const imagesRef = ref(storageRef, 'images'); // Points to 'images/space.jpg' // Note that you can use variables to create child values const fileName = 'space.jpg'; const spaceRef = ref(imagesRef, fileName); // File path is 'images/space.jpg' const path = spaceRef.fullPath; // File name is 'space.jpg' const name = spaceRef.name; // Points to 'images' const imagesRefAgain = spaceRef.parent;
Web
// Points to the root reference var storageRef = firebase.storage().ref(); // Points to 'images' var imagesRef = storageRef.child('images'); // Points to 'images/space.jpg' // Note that you can use variables to create child values var fileName = 'space.jpg'; var spaceRef = imagesRef.child(fileName); // File path is 'images/space.jpg' var path = spaceRef.fullPath; // File name is 'space.jpg' var name = spaceRef.name; // Points to 'images' var imagesRef = spaceRef.parent;
接下來,我們將說明如何上傳檔案至 Cloud Storage。