在 Web 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

為了上傳或下載檔案、刪除檔案或取得或更新元數據,您必須建立要操作的檔案的參考。可以將引用視為指向雲端中檔案的指標。引用是輕量級的,因此您可以根據需要建立任意數量的引用,並且它們還可以重複用於多個操作。

若要建立引用,請使用getStorage()取得儲存服務的實例,然後將該服務作為參數呼叫ref() 。此引用指向您的 Cloud Storage 儲存桶的根。

Web modular API

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 namespaced API

// 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();

您可以在呼叫ref()時將此路徑作為第二個參數傳遞,從而建立對樹中較低位置的引用,例如'images/space.jpg'

Web modular API

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 namespaced API

// 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"

您也可以使用parentroot屬性在檔案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。

Web modular API

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 namespaced API

// 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()parentroot可以多次連結在一起,因為每個都回傳一個參考。 rootparent是個例外,它是null

Web modular API

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 namespaced API

// 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;

參考屬性

您可以使用fullPathnamebucket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、檔案名稱以及儲存檔案的儲存桶。

Web modular API

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 namespaced API

// 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#[]*? ,因為它們不能與其他工具(例如Firebase 即時資料庫gsutil )很好地配合使用。

完整範例

Web modular API

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 namespaced API

// 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;

接下來我們來學習如何將文件上傳到雲端儲存。