Ios7 如何在objective C中设置S3ListObjectsRequest.marker以在Amazon S3中获得下一批结果？

当一个桶中有1000多个文件时，我试图获取所有文件的列表。我试过了，但没用

@try {
    S3ListObjectsRequest *req = [[S3ListObjectsRequest alloc] initWithName:bucketName];
    req.maxKeys = 2000; // Didn't do anything!
    S3ListObjectsResponse *resp = [self.s3 listObjects:req];
    NSMutableArray* objectSummaries = resp.listObjectsResult.objectSummaries;
    NSLog(@" Found a total of %d files\n",[objectSummaries count]);
    // Also didn't work
    if (resp.listObjectsResult.isTruncated) {
        req.marker = [objectSummaries objectAtIndex:999];
        S3ListObjectsResponse *resp = [self.s3 listObjects:req];
        NSMutableArray* objectSummaries = resp.listObjectsResult.objectSummaries;
        NSLog(@" Found another %d files\n",[objectSummaries count]);
    }

}

---

通过如下方式设置marker/lastKey找到答案

NSString *lastKey = @"";
// For first 1000
for (S3ObjectSummary *objectSummary in listObjectsResults.objectSummaries) {
        [objects addObject:[objectSummary key]];
        lastKey = [objectSummary key];
}

// note: got lastKey above!
while (listObjectsResults.isTruncated) {
        req = [[S3ListObjectsRequest alloc] initWithName:[self soundBucket]];
        req.marker = lastKey;
.......