Object Storage Service:Prevent overwriting objects that have the same name (iOS SDK)

Prerequisites

Before you begin, ensure that you have:

• An OSSClient instance initialized using a custom domain name, Security Token Service (STS), or another method. See Initialization (iOS SDK)

How x-oss-forbid-overwrite works

All three examples in this topic set x-oss-forbid-overwrite in a metadata dictionary. The following table summarizes how each value affects the operation:

Simple upload

The following example prevents an object from being overwritten during a simple upload:

OSSPutObjectRequest *put = [OSSPutObjectRequest new];

// Specify the bucket name. Example: examplebucket.
put.bucketName = @"examplebucket";
// Specify the full object key, excluding the bucket name. Example: exampledir/exampleobject.txt.
put.objectKey = @"exampledir/exampleobject.txt";
// Specify the full path of the local file to upload.
put.uploadingFileURL = [NSURL fileURLWithPath:@"/storage/emulated/0/oss/examplefile.txt"];

// Fail the upload if an object with the same key already exists.
put.objectMeta = @{@"x-oss-forbid-overwrite": @"true"};

// Optional: track upload progress.
put.uploadProgress = ^(int64_t bytesSent, int64_t totalByteSent, int64_t totalBytesExpectedToSend) {
    NSLog(@"%lld, %lld, %lld", bytesSent, totalByteSent, totalBytesExpectedToSend);
};

OSSTask *putTask = [client putObject:put];
[putTask continueWithBlock:^id(OSSTask *task) {
    if (!task.error) {
        NSLog(@"upload object success!");
    } else {
        NSLog(@"upload object failed, error: %@", task.error);
    }
    return nil;
}];
// [putTask waitUntilFinished];

Copy an object

The following example prevents an object from being overwritten when copying an object:

OSSCopyObjectRequest *copy = [OSSCopyObjectRequest new];
// Specify the source bucket name.
copy.sourceBucketName = @"srcbucket";
// Specify the full key of the source object.
copy.sourceObjectKey = @"dir1/srcobject.txt";
// Specify the destination bucket name.
copy.bucketName = @"destbucket";
// Specify the full key of the destination object.
copy.objectKey = @"dir2/destobject.txt";

// Fail the copy if an object with the same key already exists in the destination bucket.
copy.objectMeta = @{@"x-oss-forbid-overwrite": @"true"};

OSSTask *task = [client copyObject:copy];
[task continueWithBlock:^id(OSSTask *task) {
    if (!task.error) {
        NSLog(@"copy object success!");
    } else {
        NSLog(@"copy object failed, error: %@", task.error);
    }
    return nil;
}];
// [putTask waitUntilFinished];

Multipart upload

For multipart upload, set x-oss-forbid-overwrite in both the initiation request (init.objectMeta) and the complete request (complete.completeMetaHeader).

The following example prevents an object from being overwritten during a multipart upload:

__block NSString *uploadId = nil;
__block NSMutableArray *partInfos = [NSMutableArray new];

// Specify the bucket name. Example: examplebucket.
NSString *uploadToBucket = @"examplebucket";
// Specify the full object key, excluding the bucket name. Example: exampledir/exampleobject.txt.
NSString *uploadObjectkey = @"exampledir/exampleobject.txt";

// Initiate the multipart upload.
OSSInitMultipartUploadRequest *init = [OSSInitMultipartUploadRequest new];
init.bucketName = uploadToBucket;
init.objectKey = uploadObjectkey;

// Fail the upload if an object with the same key already exists.
init.objectMeta = @{@"x-oss-forbid-overwrite": @"true"};

// The upload ID uniquely identifies this multipart upload task. Use it to upload parts, cancel, or query the task.
OSSTask *initTask = [client multipartUploadInit:init];
[initTask waitUntilFinished];
if (!initTask.error) {
    OSSInitMultipartUploadResult *result = initTask.result;
    uploadId = result.uploadId;
} else {
    NSLog(@"multipart upload failed, error: %@", initTask.error);
    return;
}

// Upload parts.
// Specify the full path of the local file to upload.
NSString *filePath = @"/storage/emulated/0/oss/examplefile.txt";
// Get the file size.
uint64_t fileSize = [[[NSFileManager defaultManager] attributesOfItemAtPath:filePath error:nil] fileSize];
// Part numbers start from 1 and range from 1 to 10,000.
int chuckCount = *;
// Part size ranges from 100 KB to 5 GB.
uint64_t offset = fileSize / chuckCount;

for (int i = 1; i <= chuckCount; i++) {
    OSSUploadPartRequest *uploadPart = [OSSUploadPartRequest new];
    uploadPart.bucketName = uploadToBucket;
    uploadPart.objectkey = uploadObjectkey;
    uploadPart.uploadId = uploadId;
    uploadPart.partNumber = i; // part number start from 1

    NSFileHandle *readHandle = [NSFileHandle fileHandleForReadingAtPath:filePath];
    [readHandle seekToFileOffset:offset * (i - 1)];

    NSData *data = [readHandle readDataOfLength:offset];
    uploadPart.uploadPartData = data;

    OSSTask *uploadPartTask = [client uploadPart:uploadPart];
    [uploadPartTask waitUntilFinished];

    if (!uploadPartTask.error) {
        OSSUploadPartResult *result = uploadPartTask.result;
        uint64_t fileSize = [[[NSFileManager defaultManager] attributesOfItemAtPath:uploadPart.uploadPartFileURL.absoluteString error:nil] fileSize];
        [partInfos addObject:[OSSPartInfo partInfoWithPartNum:i eTag:result.eTag size:fileSize]];
    } else {
        NSLog(@"upload part error: %@", uploadPartTask.error);
        return;
    }
}

// Complete the multipart upload.
OSSCompleteMultipartUploadRequest *complete = [OSSCompleteMultipartUploadRequest new];
complete.bucketName = uploadToBucket;
complete.objectKey = uploadObjectkey;
complete.uploadId = uploadId;
complete.partInfos = partInfos;

// Fail the upload if an object with the same key already exists.
complete.completeMetaHeader = @{@"x-oss-forbid-overwrite": @"true"};

OSSTask *completeTask = [client completeMultipartUpload:complete];
[[completeTask continueWithBlock:^id(OSSTask *task) {
    if (!task.error) {
        NSLog(@"multipart upload success!");
    } else {
        NSLog(@"multipart upload error: %@", task.error);
    }
    return nil;
}] waitUntilFinished];

What's next

• PutObject — API reference for simple upload

• CopyObject — API reference for copying objects

• InitiateMultipartUpload — API reference for initiating a multipart upload

• UploadPart — API reference for uploading a part

• CompleteMultipartUpload — API reference for completing a multipart upload