您可以通过getBucketCORS查看桶的跨域规则。以下代码展示了如何查看跨域规则：

static OBSClient *client;
NSString *endPoint = @"your-endpoint";
NSString *SK = @"*** Provide your Secret Key ***";
NSString *AK = @"*** Provide your Access Key ***";
    
// 初始化身份验证
OBSStaticCredentialProvider *credentailProvider = [[OBSStaticCredentialProvider alloc] initWithAccessKey:AK secretKey:SK];
    
//初始化服务配置
OBSServiceConfiguration *conf = [[OBSServiceConfiguration alloc] initWithURLString:endPoint credentialProvider:credentailProvider];
    
// 初始化client
client = [[OBSClient alloc] initWithConfiguration:conf];
    
// 获取桶的跨域资源配置
OBSGetBucketCORSRequest *request = [[OBSGetBucketCORSRequest alloc] initWithBucketName:@"bucketname"];
    
[client getBucketCORS:request completionHandler:^(OBSGetBucketCORSResponse *response, NSError *error) {
    NSLog(@"%@",response);
}];