如何确定来自移动客户端（例如iOS）的S3存储桶上的文件是否已更改

Question

Is it possible to use AWSS3TransferManager or an alternative class to determine if a file has changed on the s3 server before downloading it?

Ideally I'd like to have some sort of automatic function that takes into account automatically the following:

• File size
• File type
• File name

or:

• File content data analysis (some sort of signature based on bit content)

Alternatively:

I see that it is possible to get the modification date for an s3 bucket , however I am not sure how this works in iOS.

Answer 1

If you want to download the file like the AWSS3TransferManager download method, you can use the alternative class AWSS3GetObjectRequest / AWSS3GetObjectOutput .

If you do not want to download the file, you can use AWSS3HeadObjectRequest / AWSS3HeadObjectOutput that will return the object's metadata or "head" of the file.

The value: lastModified will be in the AWSS3...ObjectOutput value for both class responses.