You can call setBucketWebsite to set website hosting on a bucket.

static OBSClient *client;
NSString *endPoint = @"your-endpoint";
NSString *SK = @"*** Provide your Secret Key ***";
NSString *AK = @"*** Provide your Access Key ***";
    
// Initialize identity authentication.
OBSStaticCredentialProvider *credentialProvider = [[OBSStaticCredentialProvider alloc] initWithAccessKey:AK secretKey:SK];
    
//Initialize service configuration.
OBSServiceConfiguration *conf = [[OBSServiceConfiguration alloc] initWithURLString:endPoint credentialProvider:credentialProvider];
    
// Initialize an instance of OBSClient.
client = [[OBSClient alloc] initWithConfiguration:conf];
    
    
OBSWebsiteConfCustom* redirectCustom = [OBSWebsiteConfCustom new];
    
// Configure the default homepage.
OBSWebsiteConfCustomIndexDocument* indexDocument = [[OBSWebsiteConfCustomIndexDocument alloc]initWithSuffix:@"index.html"];
// Configure the error pages.
OBSWebsiteConfCustomErrorDocument* errorDocument = [[OBSWebsiteConfCustomErrorDocument alloc]initWithKey:@"Error.html"];
    
OBSWebsiteConfCustomRoutingRule* redirectRule = [OBSWebsiteConfCustomRoutingRule new];
    
OBSWebsiteConfCustomCondition* condition = [OBSWebsiteConfCustomCondition new];
condition.keyPrefixEquals = @"docs/";
//    condition.httpErrorCodeReturnedEquals = @"404";
    
// Set the redirection rules.
OBSWebsiteConfCustomRedirect* redirect = [OBSWebsiteConfCustomRedirect new];
redirect.replaceKeyPrefixWith = @"documents/";
redirect.protocol = @"http";
redirect.hostName = @"URL";
//    redirect.replaceKeyWith = @"error.html";
redirect.httpRedirectCode = @"301";
    
    
redirectRule.condition = condition;
redirectRule.redirect = redirect;
    
[redirectCustom.indexDocumentList addObject:indexDocument];
[redirectCustom.errorDocumentList addObject:errorDocument];
[redirectCustom.routingRulesList addObject:redirectRule];
    
OBSSetBucketWebsiteRequest *request = [[OBSSetBucketWebsiteRequest alloc]initWithBucketName:@"bucketname" configuration:redirectCustom];
    
[client setBucketWebsite:request completionHandler:^(OBSSetBucketWebsiteResponse *response, NSError *error){
    NSLog(@"%@",response);
 }];

static OBSClient *client;
NSString *endPoint = @"your-endpoint";
NSString *SK = @"*** Provide your Secret Key ***";
NSString *AK = @"*** Provide your Access Key ***";
    
// Initialize identity authentication.
OBSStaticCredentialProvider *credentialProvider = [[OBSStaticCredentialProvider alloc] initWithAccessKey:AK secretKey:SK];
    
//Initialize service configuration.
OBSServiceConfiguration *conf = [[OBSServiceConfiguration alloc] initWithURLString:endPoint credentialProvider:credentialProvider];
    
// Initialize an instance of OBSClient.
client = [[OBSClient alloc] initWithConfiguration:conf];
    
// Configure that all requests will be redirected.
OBSWebsiteConfRedirectAll* redirectAll = [OBSWebsiteConfRedirectAll new];
redirectAll.hostName = @"URL";
OBSSetBucketWebsiteRequest *request = [[OBSSetBucketWebsiteRequest alloc]initWithBucketName:@"bucketname" configuration:redirectAll];
    
 [client setBucketWebsite:request completionHandler:^(OBSSetBucketWebsiteResponse *response, NSError *error){
     NSLog(@"%@",response);
 }];