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Downloading Objects
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Last updated: 2024-01-23 17:15:08
Downloading Objects
Last updated: 2024-01-23 17:15:08
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Overview

This document provides an overview of APIs and SDK code samples related to object downloads.
API
Operation
Description
Downloading an object
Downloads an object to the local file system.

SDK API References

For parameters and method description of all APIs in the SDK, please see SDK API Reference.

Advanced APIs (Recommended)

Download an object

The advanced version of the GET Object API uses more encapsulated logic to allow you to suspend, resume (via checkpoint restart), or cancel download requests.

Sample code 1. Downloading a single object

Objective-C
QCloudCOSXMLDownloadObjectRequest * request = [QCloudCOSXMLDownloadObjectRequest new];

// Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
request.bucket = @"examplebucket-1250000000";

// Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
request.object = @"exampleobject";

// Set the download URL. Once set, the file will be downloaded to the specified path
request.downloadingURL = [NSURL fileURLWithPath:@"Local File Path"];

// The size of the part of the file that has already been downloaded. Do not set this value for a new download operation
request.localCacheDownloadOffset = 100;

// Monitor the download result
[request setFinishBlock:^(id outputObject, NSError *error) {
    // `outputObject` contains all the HTTP response headers
    NSDictionary* info = (NSDictionary *) outputObject;
}];

// Monitor the download progress
[request setDownProcessBlock:^(int64_t bytesDownload,
                               int64_t totalBytesDownload,
                               int64_t totalBytesExpectedToDownload) {

    // bytesDownload                   Number of new bytes downloaded
    // totalBytesDownload              Total number of bytes received in the download
    // totalBytesExpectedToDownload    Target number of bytes expected to be downloaded
}];

[[QCloudCOSTransferMangerService defaultCOSTransferManager] DownloadObject:request];
Note:
For the complete sample, please go to GitHub.
Swift
let request : QCloudCOSXMLDownloadObjectRequest = QCloudCOSXMLDownloadObjectRequest();

// Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
request.bucket = "examplebucket-1250000000";

// Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
request.object = "exampleobject";

// Set the download URL. Once set, the file will be downloaded to the specified path
request.downloadingURL = NSURL.fileURL(withPath: "Local File Path") as URL?;

// The size of the part of the file that has already been downloaded. Do not set this value for a new download operation
request.localCacheDownloadOffset = 100;

// Monitor the download progress
request.sendProcessBlock = { (bytesDownload, totalBytesDownload,
    totalBytesExpectedToDownload) in

    // bytesDownload                   Number of new bytes downloaded
    // totalBytesDownload              Total number of bytes received in the download
    // totalBytesExpectedToDownload    Target number of bytes expected to be downloaded
}

// Monitor the download result
request.finishBlock = { (result, error) in
    if let result = result {
        // "result" contains response headers.
    } else {
        print(error!);
    }
}

QCloudCOSTransferMangerService.defaultCOSTransferManager().downloadObject(request);
Note:
For the complete sample, please go to GitHub.

Sample code 2. Suspending, resuming, or canceling a download

Objective-C
To suspend a download, use the code below:
[request cancel];
To resume a suspended download, use the code below:
// Size of the downloaded part of the file
int64_t localCacheDownloadOffset = 0;
request.localCacheDownloadOffset = localCacheDownloadOffset;
To cancel a download, use the code below:
[request cancel];
Note:
For the complete sample, please go to GitHub.
Swift
To suspend a download, use the code below:
request.cancel();
To resume a suspended download, use the code below:
// Size of the downloaded part of the file

let localCacheDownloadOffset = 100;
request.localCacheDownloadOffset = Int64(localCacheDownloadOffset);
To cancel a download, use the code below:
request.cancel();
Note:
For the complete sample, please go to GitHub.

Sample code 3. Resumable download

Objective-C
   QCloudCOSXMLDownloadObjectRequest *getObjectRequest = [[QCloudCOSXMLDownloadObjectRequest alloc] init];
    // Enable resumable download. Resumable download is disabled by default
    getObjectRequest.resumableDownload = true;
    // Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
    getObjectRequest.bucket = transferTestBucket.name;
    // Set the download URL. Once set, the file will be downloaded to the specified path
    getObjectRequest.downloadingURL = [NSURL URLWithString:QCloudTempFilePathWithExtension(@"downding")];
    // Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
    getObjectRequest.object = put.object;
    // Monitor the download result
    [getObjectRequest setFinishBlock:^(id outputObject, NSError *error) {
        // `outputObject` contains all the HTTP response headers
        NSDictionary* info = (NSDictionary *) outputObject;
    }];

    // Monitor the download progress
    [getObjectRequest setDownProcessBlock:^(int64_t bytesDownload,
                                   int64_t totalBytesDownload,
                                   int64_t totalBytesExpectedToDownload) {

        // bytesDownload                   Number of new bytes downloaded
        // totalBytesDownload              Total number of bytes received in the download
        // totalBytesExpectedToDownload    Target number of bytes expected to be downloaded
    }];

    [[QCloudCOSTransferMangerService costransfermangerServiceForKey:kHTTPServiceKey] DownloadObject:getObjectRequest];
Note:
For the complete sample, please go to GitHub.
Swift
        let request : QCloudCOSXMLDownloadObjectRequest = QCloudCOSXMLDownloadObjectRequest();

        // Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
        request.bucket = "examplebucket-1250000000";

        // Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
        request.object = "exampleobject";

        request.resumableDownload = true;
        // Set the download URL. Once set, the file will be downloaded to the specified path
        request.downloadingURL = NSURL.fileURL(withPath: "Local File Path") as URL?;

        // The size of the part of the file that has already been downloaded. Do not set this value for a new download operation
        request.localCacheDownloadOffset = 100;

        // Monitor the download progress
        request.sendProcessBlock = { (bytesDownload, totalBytesDownload,
            totalBytesExpectedToDownload) in

            // bytesDownload                   Number of new bytes downloaded
            // totalBytesDownload              Total number of bytes received in the download
            // totalBytesExpectedToDownload    Target number of bytes expected to be downloaded
        }

        // Monitor the download result
        request.finishBlock = { (result, error) in
            if let result = result {
                // "result" contains response headers.
            } else {
                print(error!);
            }
        }

    QCloudCOSTransferMangerService.defaultCOSTransferManager().downloadObject(request);
}
Note:
For the complete sample, please go to GitHub.

Sample code 4. Batch download

Objective-C
for (int i = 0; i<20; i++) {
    QCloudCOSXMLDownloadObjectRequest * request = [QCloudCOSXMLDownloadObjectRequest new];

    // Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
    request.bucket = @"examplebucket-1250000000";

   // Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
    request.object = @"exampleobject";

    // Set the download URL. Once set, the file will be downloaded to the specified path
    request.downloadingURL = [NSURL fileURLWithPath:@"Local File Path"];

    // The size of the part of the file that has already been downloaded. Do not set this value for a new download operation
    request.localCacheDownloadOffset = 100;

    // Monitor the download result
    [request setFinishBlock:^(id outputObject, NSError *error) {
        // `outputObject` contains all the HTTP response headers
        NSDictionary* info = (NSDictionary *) outputObject;
    }];

    // Monitor the download progress
    [request setDownProcessBlock:^(int64_t bytesDownload,
                                   int64_t totalBytesDownload,
                                   int64_t totalBytesExpectedToDownload) {

        // bytesDownload                   Number of new bytes downloaded
        // totalBytesDownload              Total number of bytes received in the download
        // totalBytesExpectedToDownload    Target number of bytes expected to be downloaded
    }];

    [[QCloudCOSTransferMangerService defaultCOSTransferManager] DownloadObject:request];
}
Note:
For the complete sample, please go to GitHub.
Swift
for i in 1...10 {
    let request : QCloudCOSXMLDownloadObjectRequest = QCloudCOSXMLDownloadObjectRequest();

    // Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
    request.bucket = "examplebucket-1250000000";

    // Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
    request.object = "exampleobject";

    // Set the download URL. Once set, the file will be downloaded to the specified path
    request.downloadingURL = NSURL.fileURL(withPath: "Local File Path") as URL?;

    // The size of the part of the file that has already been downloaded. Do not set this value for a new download operation
    request.localCacheDownloadOffset = 100;

    // Monitor the download progress
    request.sendProcessBlock = { (bytesDownload, totalBytesDownload,
        totalBytesExpectedToDownload) in

        // bytesDownload                   Number of new bytes downloaded
        // totalBytesDownload              Total number of bytes received in the download
        // totalBytesExpectedToDownload    Target number of bytes expected to be downloaded
    }

    // Monitor the download result
    request.finishBlock = { (result, error) in
        if let result = result {
            // "result" contains response headers.
        } else {
            print(error!);
        }
    }

    QCloudCOSTransferMangerService.defaultCOSTransferManager().downloadObject(request);
}
Note:
For the complete sample, please go to GitHub.

Sample code 5. Downloading a folder and files contained

Objective-C
    QCloudGetBucketRequest* request = [QCloudGetBucketRequest new];

    // Bucket name in the format: `BucketName-APPID`
    request.bucket = @"examplebucket-1250000000";
    // Maximum number of objects to return at a time. Default value: 1000
    request.maxKeys = 100;

    // The full path of a COS folder to be downloaded

    request.prefix = @"cos_path";


    [request setFinishBlock:^(QCloudListBucketResult * result, NSError* error) {
        if(!error){
            for (QCloudBucketContents *content in result.contents) {
                QCloudCOSXMLDownloadObjectRequest * request = [QCloudCOSXMLDownloadObjectRequest new];

                // Bucket name in the format: `BucketName-APPID`
                request.bucket = @"examplebucket-1250000000";

                // Object key, i.e., the full path of a COS object. If the object is in a directory, the path should be "dir1/object1".
                request.object = content.key;

                // Set the download URL. Once set, the file will be downloaded to the specified path
                request.downloadingURL = [NSURL fileURLWithPath:[@"Local File Path" stringByAppendingFormat:@"/%@",content.key]];

                // Monitor the download result
                [request setFinishBlock:^(id outputObject, NSError *error) {
                    // `outputObject` contains all the HTTP response headers
                    NSDictionary* info = (NSDictionary *) outputObject;
                }];

                // Monitor the download progress
                [request setDownProcessBlock:^(int64_t bytesDownload,
                                               int64_t totalBytesDownload,
                                               int64_t totalBytesExpectedToDownload) {

                    // bytesDownload                   Number of new bytes downloaded
                    // totalBytesDownload              Total number of bytes received in the download
                    // totalBytesExpectedToDownload    Target number of bytes expected to be downloaded
                }];

                [[QCloudCOSTransferMangerService defaultCOSTransferManager] DownloadObject:request];
            }


        }
    }];

    [[QCloudCOSXMLService defaultCOSXML] GetBucket:request];
Note:
For the complete sample, please go to GitHub.
Swift
        let getBucketReq = QCloudGetBucketRequest.init();

        // Bucket name in the format: `BucketName-APPID`
        getBucketReq.bucket = "examplebucket-1250000000";

        // Maximum number of objects to return at a time. Default value: 1000
        getBucketReq.maxKeys = 100;

        // The full path of a COS folder to be downloaded
        getBucketReq.prefix = "cos_path";

        getBucketReq.setFinish { (result, error) in
            if let result = result {
                let contents = result.contents;
                for content in contents {
                    let info = QCloudDeleteObjectInfo.init();
                    let request : QCloudCOSXMLDownloadObjectRequest = QCloudCOSXMLDownloadObjectRequest();

                    // Bucket name in the format: `BucketName-APPID`
                    request.bucket = "examplebucket-1250000000";

                    // Object key, i.e., the full path of a COS object. If the object is in a directory, the path should be "dir1/object1".
                    request.object = content.key;

                    // Set the download URL. Once set, the file will be downloaded to the specified path

                    request.downloadingURL = NSURL.fileURL(withPath: "Local File Path" ) as URL?;

                    // The size of the part of the file that has already been downloaded. Do not set this value for a new download operation
                    request.localCacheDownloadOffset = 100;

                    // Monitor the download progress
                    request.sendProcessBlock = { (bytesDownload, totalBytesDownload,
                        totalBytesExpectedToDownload) in

                        // bytesDownload                   Number of new bytes downloaded
                        // totalBytesDownload              Total number of bytes received in the download
                        // totalBytesExpectedToDownload    Target number of bytes expected to be downloaded
                    }

                    // Monitor the download result
                    request.finishBlock = { (result, error) in
                        if let result = result {
                            // "result" contains response headers.
                        } else {
                            print(error!);
                        }
                    }

                    QCloudCOSTransferMangerService.defaultCOSTransferManager().downloadObject(request);
                }
            } else {
                print(error!);
            }
        }
        QCloudCOSXMLService.defaultCOSXML().getBucket(getBucketReq);
Note:
For the complete sample, please go to GitHub.

Sample code 6. Limiting the download speed

Note:
COS iOS SDK v5.9.5 or later is required.
Objective-C
QCloudCOSXMLDownloadObjectRequest * request = [QCloudCOSXMLDownloadObjectRequest new];

// Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
request.bucket = @"examplebucket-1250000000";

// Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
request.object = @"exampleobject";

// Set the download URL. Once set, the file will be downloaded to the specified path
request.downloadingURL = [NSURL fileURLWithPath:@"Local File Path"];

// The size of the part of the file that has already been downloaded. Do not set this value for a new download operation
request.localCacheDownloadOffset = 100;

// Use `TrafficLimit` to limit the download speed, in bit/s. The speed range is 819200 to 838860800, that is, 100 KB/s to 100 MB/s.
request.trafficLimit = 819200;

// Monitor the download result
[request setFinishBlock:^(id outputObject, NSError *error) {
    // `outputObject` contains all the HTTP response headers
    NSDictionary* info = (NSDictionary *) outputObject;
}];

// Monitor the download progress
[request setDownProcessBlock:^(int64_t bytesDownload,
                               int64_t totalBytesDownload,
                               int64_t totalBytesExpectedToDownload) {

    // bytesDownload                   Number of new bytes downloaded
    // totalBytesDownload              Total number of bytes received in the download
    // totalBytesExpectedToDownload    Target number of bytes expected to be downloaded
}];

[[QCloudCOSTransferMangerService defaultCOSTransferManager] DownloadObject:request];
Note:
For the complete sample, please go to GitHub.
Swift
let request : QCloudCOSXMLDownloadObjectRequest = QCloudCOSXMLDownloadObjectRequest();

// Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
request.bucket = "examplebucket-1250000000";

// Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
request.object = "exampleobject";

// Set the download URL. Once set, the file will be downloaded to the specified path
request.downloadingURL = NSURL.fileURL(withPath: "Local File Path") as URL?;

// The size of the part of the file that has already been downloaded. Do not set this value for a new download operation
request.localCacheDownloadOffset = 100;

// Use `TrafficLimit` to limit the download speed, in bit/s. The speed range is 819200 to 838860800, that is, 100 KB/s to 100 MB/s.
request.trafficLimit = 819200;

// Monitor the download progress
request.sendProcessBlock = { (bytesDownload, totalBytesDownload,
    totalBytesExpectedToDownload) in

    // bytesDownload                   Number of new bytes downloaded
    // totalBytesDownload              Total number of bytes received in the download
    // totalBytesExpectedToDownload    Target number of bytes expected to be downloaded
}

// Monitor the download result
request.finishBlock = { (result, error) in
    if let result = result {
        // "result" contains response headers.
    } else {
        print(error!);
    }
}

QCloudCOSTransferMangerService.defaultCOSTransferManager().downloadObject(request);
Note:
For the complete sample, please go to GitHub.

Simple Operations

Download an object

Description

This API is used to download an object to the local file system.

Sample code 1. Downloading an object

Objective-C
QCloudGetObjectRequest* request = [QCloudGetObjectRequest new];

// Set the download URL. Once set, the file will be downloaded to the specified path
request.downloadingURL = [NSURL URLWithString:QCloudTempFilePathWithExtension(@"downding")];

// Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
request.object = @"exampleobject";

// Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
request.bucket = @"examplebucket-1250000000";

[request setFinishBlock:^(id outputObject, NSError *error) {
    // outputObject contains information such as the ETag or custom headers in the response.
    NSDictionary* info = (NSDictionary *) outputObject;
    // The CRC64 value of a server object
    result[@"x-cos-hash-crc64ecma"] 
    // The CRC64 value of a downloaded local object. If the returned CRC64 value is consistent with the local calculation, the downloaded object is the same as the server object.
    uint64_t localCrc64 = [Local object data qcloud_crc64];
}];
[request setDownProcessBlock:^(int64_t bytesDownload, int64_t totalBytesDownload,
    int64_t totalBytesExpectedToDownload) {

    // Download progress
    // bytesDownload       Number of downloaded bytes
    // totalBytesDownload  Total number of bytes received for the download
    // totalBytesExpectedToDownload Total number of bytes in the file

}];

[[QCloudCOSXMLService defaultCOSXML] GetObject:request];
Note:
For the complete sample, go to GitHub.
Swift
let getObject = QCloudGetObjectRequest.init();

// Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
getObject.bucket = "examplebucket-1250000000";

// Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
getObject.object = "exampleobject";
// Set the download URL. Once set, the file will be downloaded to the specified path
getObject.downloadingURL = URL.init(string: NSTemporaryDirectory())!
    .appendingPathComponent(getObject.object);
getObject.finishBlock = {(result,error) in
    if let result = result {
        // The CRC64 value of a server object
        result["x-cos-hash-crc64ecma"] 
        // The CRC64 value of a downloaded local object. If the returned CRC64 value is consistent with the local calculation, the downloaded object is the same as the server object.
        uint64_t localCrc64 = Local object data.qcloud_crc64();
    } else {
        print(error!);
    }
};
getObject.downProcessBlock = {(bytesDownload, totalBytesDownload,
    totalBytesExpectedToDownload) in
    // bytesDownload       Number of downloaded bytes
    // totalBytesDownload  Total number of bytes received for the download
    // totalBytesExpectedToDownload Total number of bytes in the file
}
QCloudCOSXMLService.defaultCOSXML().getObject(getObject);
Note:
For the complete sample, go to GitHub.

Sample code 2. Limiting the download speed

Note:
COS iOS SDK v5.9.5 or later is required.
Objective-C
QCloudGetObjectRequest* request = [QCloudGetObjectRequest new];

// Set the download URL. Once set, the file will be downloaded to the specified path
request.downloadingURL = [NSURL URLWithString:QCloudTempFilePathWithExtension(@"downding")];

// Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
request.object = @"exampleobject";

// Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
request.bucket = @"examplebucket-1250000000";

// Use `TrafficLimit` to limit the download speed, in bit/s. The speed range is 819200 to 838860800, that is, 100 KB/s to 100 MB/s.
request.trafficLimit = 819200;

[request setFinishBlock:^(id outputObject, NSError *error) {
    // outputObject contains information such as the ETag or custom headers in the response.
    NSDictionary* info = (NSDictionary *) outputObject;
    // Obtain the CRC64 value of the object.
    NSString * crc64 = [[outputObject __originHTTPURLResponse__].allHeaderFields valueForKey:@"x-cos-hash-crc64ecma"];
}];
[request setDownProcessBlock:^(int64_t bytesDownload, int64_t totalBytesDownload,
    int64_t totalBytesExpectedToDownload) {

    // Download progress
    // bytesDownload       Number of downloaded bytes
    // totalBytesDownload  Total number of bytes received for the download
    // totalBytesExpectedToDownload Total number of bytes in the file

}];

[[QCloudCOSXMLService defaultCOSXML] GetObject:request];
Note:
For the complete sample, go to GitHub.
Swift
let getObject = QCloudGetObjectRequest.init();

// Bucket name in the format of BucketName-Appid, which can be viewed in the COS console at https://console.cloud.tencent.com/cos5/bucket
getObject.bucket = "examplebucket-1250000000";

// Object key, i.e. the full path of a COS object. If the object is in a directory, the path should be "video/xxx/movie.mp4"
getObject.object = "exampleobject";
// Set the download URL. Once set, the file will be downloaded to the specified path
getObject.downloadingURL = URL.init(string: NSTemporaryDirectory())!
    .appendingPathComponent(getObject.object);

// Use `TrafficLimit` to limit the download speed, in bit/s. The speed range is 819200 to 838860800, that is, 100 KB/s to 100 MB/s.
getObject.trafficLimit = 819200;

getObject.finishBlock = {(result,error) in
    if let result = result {
        // "result" contains response headers.
        // Obtain the CRC64 value of the object.
        let crc64 = result?.__originHTTPURLResponse__.allHeaderFields["x-cos-hash-crc64ecma"];
    } else {
        print(error!);
    }
};
getObject.downProcessBlock = {(bytesDownload, totalBytesDownload,
    totalBytesExpectedToDownload) in
    // bytesDownload       Number of downloaded bytes
    // totalBytesDownload  Total number of bytes received for the download
    // totalBytesExpectedToDownload Total number of bytes in the file
}
QCloudCOSXMLService.defaultCOSXML().getObject(getObject);
Note:
For the complete sample, go to GitHub.
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