向 Cloud Storage 上传文件（Apple 平台）

Cloud Storage for Firebase 可让您快速轻松地将文件上传到 Firebase 提供和管理的 Cloud Storage 存储桶中。

创建引用

要上传文件，请首先创建一个 Cloud Storage 引用，指向 Cloud Storage 中您希望将文件上传到的位置。

您可以通过将子路径附加到 Cloud Storage 存储桶的根目录来创建引用：

Swift

// Create a root reference
let storageRef = storage.reference()

// Create a reference to "mountains.jpg"
let mountainsRef = storageRef.child("mountains.jpg")

// Create a reference to 'images/mountains.jpg'
let mountainImagesRef = storageRef.child("images/mountains.jpg")

// While the file names are the same, the references point to different files
mountainsRef.name == mountainImagesRef.name            // true
mountainsRef.fullPath == mountainImagesRef.fullPath    // false

Objective-C

// Create a root reference
FIRStorageReference *storageRef = [storage reference];

// Create a reference to "mountains.jpg"
FIRStorageReference *mountainsRef = [storageRef child:@"mountains.jpg"];

// Create a reference to 'images/mountains.jpg'
FIRStorageReference *mountainImagesRef = [storageRef child:@"images/mountains.jpg"];

// While the file names are the same, the references point to different files
[mountainsRef.name isEqualToString:mountainImagesRef.name];         // true
[mountainsRef.fullPath isEqualToString:mountainImagesRef.fullPath]; // false

您无法通过指向 Cloud Storage 存储桶根目录的引用来上传数据。您的引用必须指向一个子网址。

上传文件

有了引用之后，您可以通过两种方式将文件上传到 Cloud Storage：

从内存中的数据上传
从表示设备上某个文件的网址上传

从内存中的数据上传

putData:metadata:completion: 方法是将文件上传到 Cloud Storage 最简单的方法。putData:metadata:completion: 接受 NSData 对象作为参数并会返回 FIRStorageUploadTask，它可用于管理上传并监控其状态。

Swift

// Data in memory
let data = Data()

// Create a reference to the file you want to upload
let riversRef = storageRef.child("images/rivers.jpg")

// Upload the file to the path "images/rivers.jpg"
let uploadTask = riversRef.putData(data, metadata: nil) { (metadata, error) in
  guard let metadata = metadata else {
    // Uh-oh, an error occurred!
    return
  }
  // Metadata contains file metadata such as size, content-type.
  let size = metadata.size
  // You can also access to download URL after upload.
  riversRef.downloadURL { (url, error) in
    guard let downloadURL = url else {
      // Uh-oh, an error occurred!
      return
    }
  }
}

Objective-C

// Data in memory
NSData *data = [NSData dataWithContentsOfFile:@"rivers.jpg"];

// Create a reference to the file you want to upload
FIRStorageReference *riversRef = [storageRef child:@"images/rivers.jpg"];

// Upload the file to the path "images/rivers.jpg"
FIRStorageUploadTask *uploadTask = [riversRef putData:data
                                             metadata:nil
                                           completion:^(FIRStorageMetadata *metadata,
                                                        NSError *error) {
  if (error != nil) {
    // Uh-oh, an error occurred!
  } else {
    // Metadata contains file metadata such as size, content-type, and download URL.
    int size = metadata.size;
    // You can also access to download URL after upload.
    [riversRef downloadURLWithCompletion:^(NSURL * _Nullable URL, NSError * _Nullable error) {
      if (error != nil) {
        // Uh-oh, an error occurred!
      } else {
        NSURL *downloadURL = URL;
      }
    }];
  }
}];

从本地文件上传

您可以使用 putFile:metadata:completion: 方法上传设备上的本地文件，如相机中的照片和视频。 putFile:metadata:completion: 接受 NSURL 作为参数并会返回 FIRStorageUploadTask，它可用于管理上传并监控其状态。

Swift

// File located on disk
let localFile = URL(string: "path/to/image")!

// Create a reference to the file you want to upload
let riversRef = storageRef.child("images/rivers.jpg")

// Upload the file to the path "images/rivers.jpg"
let uploadTask = riversRef.putFile(from: localFile, metadata: nil) { metadata, error in
  guard let metadata = metadata else {
    // Uh-oh, an error occurred!
    return
  }
  // Metadata contains file metadata such as size, content-type.
  let size = metadata.size
  // You can also access to download URL after upload.
  riversRef.downloadURL { (url, error) in
    guard let downloadURL = url else {
      // Uh-oh, an error occurred!
      return
    }
  }
}

Objective-C

// File located on disk
NSURL *localFile = [NSURL URLWithString:@"path/to/image"];

// Create a reference to the file you want to upload
FIRStorageReference *riversRef = [storageRef child:@"images/rivers.jpg"];

// Upload the file to the path "images/rivers.jpg"
FIRStorageUploadTask *uploadTask = [riversRef putFile:localFile metadata:nil completion:^(FIRStorageMetadata *metadata, NSError *error) {
  if (error != nil) {
    // Uh-oh, an error occurred!
  } else {
    // Metadata contains file metadata such as size, content-type, and download URL.
    int size = metadata.size;
    // You can also access to download URL after upload.
    [riversRef downloadURLWithCompletion:^(NSURL * _Nullable URL, NSError * _Nullable error) {
      if (error != nil) {
        // Uh-oh, an error occurred!
      } else {
        NSURL *downloadURL = URL;
      }
    }];
  }
}];

如果要主动管理上传任务，您可以使用 putData: 或 putFile: 方法并观测上传任务，而不是使用完成处理程序。如需了解详情，请参阅管理上传。

添加文件元数据

在上传文件时，您还可以包含元数据。这些元数据包含典型的文件元数据属性，如 name、size 和 contentType（通常称为 MIME 类型）。putFile: 方法会自动根据 NSURL 文件扩展名推断内容类型，但您可以通过在元数据中指定 contentType 来替换自动检测到的类型。如果您未提供 contentType，并且 Cloud Storage 无法根据文件扩展名推断出默认值，Cloud Storage 将使用 application/octet-stream。如需详细了解文件元数据，请参阅使用文件元数据部分。

Swift

// Create storage reference
let mountainsRef = storageRef.child("images/mountains.jpg")

// Create file metadata including the content type
let metadata = StorageMetadata()
metadata.contentType = "image/jpeg"

// Upload data and metadata
mountainsRef.putData(data, metadata: metadata)

// Upload file and metadata
mountainsRef.putFile(from: localFile, metadata: metadata)

Objective-C

// Create storage reference
FIRStorageReference *mountainsRef = [storageRef child:@"images/mountains.jpg"];

// Create file metadata including the content type
FIRStorageMetadata *metadata = [[FIRStorageMetadata alloc] init];
metadata.contentType = @"image/jpeg";

// Upload data and metadata
FIRStorageUploadTask *uploadTask = [mountainsRef putData:data metadata:metadata];

// Upload file and metadata
uploadTask = [mountainsRef putFile:localFile metadata:metadata];

管理上传

除了启动上传外，您还可以分别使用 pause、resume 和 cancel 方法来暂停、继续和取消上传。这些方法会引发 pause、resume 和 cancel 事件。取消上传会导致上传失败，并显示一条错误指明上传已被取消。

Swift

// Start uploading a file
let uploadTask = storageRef.putFile(from: localFile)

// Pause the upload
uploadTask.pause()

// Resume the upload
uploadTask.resume()

// Cancel the upload
uploadTask.cancel()

Objective-C

// Start uploading a file
FIRStorageUploadTask *uploadTask = [storageRef putFile:localFile];

// Pause the upload
[uploadTask pause];

// Resume the upload
[uploadTask resume];

// Cancel the upload
[uploadTask cancel];

监控上传进度

您可以向 FIRStorageUploadTask 附加观测器，以便监控上传的进度。添加观测器后会返回一个 FIRStorageHandle，它可用于移除此观测器。

Swift

// Add a progress observer to an upload task
let observer = uploadTask.observe(.progress) { snapshot in
  // A progress event occured
}

Objective-C

// Add a progress observer to an upload task
FIRStorageHandle observer = [uploadTask observeStatus:FIRStorageTaskStatusProgress
                                              handler:^(FIRStorageTaskSnapshot *snapshot) {
                                                // A progress event occurred
                                              }];

这些观测器可以添加至 FIRStorageTaskStatus 事件：

`FIRStorageTaskStatus` 事件	典型用法
`FIRStorageTaskStatusResume`	此事件在任务开始或恢复上传时触发，通常与 `FIRStorageTaskStatusPause` 事件结合使用。
`FIRStorageTaskStatusProgress`	每次向 Cloud Storage 上传数据时，此事件都会触发，并且可用于为上传进度指示器提供所需数据。
`FIRStorageTaskStatusPause`	每次上传暂停时都会触发此事件，通常与 `FIRStorageTaskStatusResume` 事件结合使用。
`FIRStorageTaskStatusSuccess`	此事件会在上传成功完成时触发。
`FIRStorageTaskStatusFailure`	当上传失败时会触发此事件。请检查错误以确定失败原因。

当有事件发生时，系统将传回 FIRStorageTaskSnapshot 对象。此快照是事件发生时的任务视图，该视图不可改变。此对象包含以下属性：

属性	类型	说明
`progress`	`NSProgress`	包含上传进度的 `NSProgress` 对象。
`error`	`NSError`	上传期间发生的错误（如果有）。
`metadata`	`FIRStorageMetadata`	在上传期间，此属性包含要上传的元数据。在 `FIRTaskStatusSuccess` 事件发生后，此属性包含已上传文件的元数据。
`task`	`FIRStorageUploadTask`	快照所对应的任务，可用于管理（使用 `pause` 暂停、使用 `resume` 继续、使用 `cancel` 取消）任务。
`reference`	`FIRStorageReference`	此任务的来源引用。

您可以逐个移除观察者，也可以按状态移除或是全部移除。

Swift

// Create a task listener handle
let observer = uploadTask.observe(.progress) { snapshot in
  // A progress event occurred
}

// Remove an individual observer
uploadTask.removeObserver(withHandle: observer)

// Remove all observers of a particular status
uploadTask.removeAllObservers(for: .progress)

// Remove all observers
uploadTask.removeAllObservers()

Objective-C

// Create a task listener handle
FIRStorageHandle observer = [uploadTask observeStatus:FIRStorageTaskStatusProgress
                                              handler:^(FIRStorageTaskSnapshot *snapshot) {
                                                // A progress event occurred
                                              }];

// Remove an individual observer
[uploadTask removeObserverWithHandle:observer];

// Remove all observers of a particular status
[uploadTask removeAllObserversForStatus:FIRStorageTaskStatusProgress];

// Remove all observers
[uploadTask removeAllObservers];

为了防止内存泄漏，所有观测器在发生 FIRStorageTaskStatusSuccess 或 FIRStorageTaskStatusFailure 后都会被移除。

错误处理

导致上传时出现错误的原因有很多，包括本地文件不存在，或者用户不具备上传所需文件的权限。如需了解错误详情，请参阅相关文档的处理错误部分。

完整示例

下面是一个包含进度监控和错误处理的完整上传示例：

Swift

// Local file you want to upload
let localFile = URL(string: "path/to/image")!

// Create the file metadata
let metadata = StorageMetadata()
metadata.contentType = "image/jpeg"

// Upload file and metadata to the object 'images/mountains.jpg'
let uploadTask = storageRef.putFile(from: localFile, metadata: metadata)

// Listen for state changes, errors, and completion of the upload.
uploadTask.observe(.resume) { snapshot in
  // Upload resumed, also fires when the upload starts
}

uploadTask.observe(.pause) { snapshot in
  // Upload paused
}

uploadTask.observe(.progress) { snapshot in
  // Upload reported progress
  let percentComplete = 100.0 * Double(snapshot.progress!.completedUnitCount)
    / Double(snapshot.progress!.totalUnitCount)
}

uploadTask.observe(.success) { snapshot in
  // Upload completed successfully
}

uploadTask.observe(.failure) { snapshot in
  if let error = snapshot.error as? NSError {
    switch (StorageErrorCode(rawValue: error.code)!) {
    case .objectNotFound:
      // File doesn't exist
      break
    case .unauthorized:
      // User doesn't have permission to access file
      break
    case .cancelled:
      // User canceled the upload
      break

    /* ... */

    case .unknown:
      // Unknown error occurred, inspect the server response
      break
    default:
      // A separate error occurred. This is a good place to retry the upload.
      break
    }
  }
}

Objective-C

// Local file you want to upload
NSURL *localFile = [NSURL URLWithString:@"path/to/image"];

// Create the file metadata
FIRStorageMetadata *metadata = [[FIRStorageMetadata alloc] init];
metadata.contentType = @"image/jpeg";

// Upload file and metadata to the object 'images/mountains.jpg'
FIRStorageUploadTask *uploadTask = [storageRef putFile:localFile metadata:metadata];

// Listen for state changes, errors, and completion of the upload.
[uploadTask observeStatus:FIRStorageTaskStatusResume handler:^(FIRStorageTaskSnapshot *snapshot) {
  // Upload resumed, also fires when the upload starts
}];

[uploadTask observeStatus:FIRStorageTaskStatusPause handler:^(FIRStorageTaskSnapshot *snapshot) {
  // Upload paused
}];

[uploadTask observeStatus:FIRStorageTaskStatusProgress handler:^(FIRStorageTaskSnapshot *snapshot) {
  // Upload reported progress
  double percentComplete = 100.0 * (snapshot.progress.completedUnitCount) / (snapshot.progress.totalUnitCount);
}];

[uploadTask observeStatus:FIRStorageTaskStatusSuccess handler:^(FIRStorageTaskSnapshot *snapshot) {
  // Upload completed successfully
}];

// Errors only occur in the "Failure" case
[uploadTask observeStatus:FIRStorageTaskStatusFailure handler:^(FIRStorageTaskSnapshot *snapshot) {
  if (snapshot.error != nil) {
    switch (snapshot.error.code) {
      case FIRStorageErrorCodeObjectNotFound:
        // File doesn't exist
        break;

      case FIRStorageErrorCodeUnauthorized:
        // User doesn't have permission to access file
        break;

      case FIRStorageErrorCodeCancelled:
        // User canceled the upload
        break;

      /* ... */

      case FIRStorageErrorCodeUnknown:
        // Unknown error occurred, inspect the server response
        break;
    }
  }
}];

现在您已经上传了文件，接下来，我们将学习如何从 Cloud Storage 下载文件。