(Objective-C) Azure Blob - Get Tags (Check if Blob Exists)

See more Azure Cloud Storage Examples

Gets the user-defined tags for a specified blob. This can also be used as a way to check to see if a blob exists.

For more information, see https://learn.microsoft.com/en-us/rest/api/storageservices/get-blob-tags

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#import <CkoRest.h>
#import <CkoAuthAzureStorage.h>
#import <CkoStringBuilder.h>
#import <CkoXml.h>

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

CkoRest *rest = [[CkoRest alloc] init];

// Connect to the Azure Storage Blob Service
BOOL bTls = YES;
int port = 443;
BOOL bAutoReconnect = YES;
// In this example, the storage account name is "chilkat".
BOOL success = [rest Connect: @"chilkat.blob.core.windows.net" port: [NSNumber numberWithInt: port] tls: bTls autoReconnect: bAutoReconnect];
if (success != YES) {
    NSLog(@"%@",rest.LastErrorText);
    return;
}

// Provide Azure Cloud credentials for the REST call.
CkoAuthAzureStorage *azAuth = [[CkoAuthAzureStorage alloc] init];
azAuth.AccessKey = @"AZURE_ACCESS_KEY";
// The account name used here should match the 1st part of the domain passed in the call to Connect (above).
azAuth.Account = @"chilkat";
azAuth.Scheme = @"SharedKey";
azAuth.Service = @"Blob";
// This causes the "x-ms-version: 2021-08-06" header to be automatically added.
azAuth.XMsVersion = @"2021-08-06";
success = [rest SetAuthAzureStorage: azAuth];

// Note: The application does not need to explicitly set the following
// headers: Content-Length, x-ms-date, Authorization.  These headers
// are automatically set by Chilkat.

// The Azure blob container is "test", the file is "helloWorld.txt"
// Add "?comp=tags" to get the user-defined tags instead of the actual blob content.
CkoStringBuilder *sb = [[CkoStringBuilder alloc] init];
success = [rest FullRequestNoBodySb: @"GET" uriPath: @"/test/helloWorldajdfadf.txt?comp=tags" sb: sb];
if (success == NO) {
    // Examine the request/response to see what happened.
    NSLog(@"%@%d",@"response status code = ",[rest.ResponseStatusCode intValue]);
    NSLog(@"%@%@",@"response status text = ",rest.ResponseStatusText);
    NSLog(@"%@%@",@"response header: ",rest.ResponseHeader);
    NSLog(@"%@",@"---");
    NSLog(@"%@%@",@"LastRequestStartLine: ",rest.LastRequestStartLine);
    NSLog(@"%@%@",@"LastRequestHeader: ",rest.LastRequestHeader);
    return;
}

// A typical blob with no tags will return this:

// <?xml version="1.0" encoding="utf-8"?>
// <Tags><TagSet/></Tags>

// If the blob does not exist, you get this:

// <?xml version="1.0" encoding="utf-8"?>
// <Error>
//     <Code>BlobNotFound</Code>
//     <Message>The specified blob does not exist.
// 	RequestId:fcfefdd9-301e-001a-2135-3a23d2000000
// 	Time:2023-02-06T14:17:00.7805577Z
//     </Message>
// </Error>

NSLog(@"%@",[sb GetAsString]);

// To see if we got Tags or an Error, then examine the XML.
CkoXml *xml = [[CkoXml alloc] init];
[xml LoadSb: sb autoTrim: YES];

// Examine the tag..
if ([xml TagEquals: @"Tags"] == YES) {
    NSLog(@"%@",@"Blob exists!");
}
else {

    if ([xml ChildContentMatches: @"Code" pattern: @"BlobNotFound" caseSensitive: YES] == YES) {
        NSLog(@"%@",@"Blob does not exist.");
    }
    else {
        NSLog(@"%@",@"Some other error...");
    }

}

NSLog(@"%@",@"Success.");