Thanks, David.
My server side is C++ and I understand/see the issue by not using
pointers. So it would indeed by a far-reaching change.
I'll look into your 'filesystem' approach as a possible workaround.
Thanks!
Paul
On Aug 4, 2009, at 10:13 AM, David Reiss wrote:
The biggest problem in the languages that I'm familiar with is
C++. Unlike Protocol Buffers, we store members directly in our
structures (rather than by pointers), so our members are not
nullable. Therefore, it is impossible to have something like
struct Folder {
optional 1: Folder parent;
}
since that would require infinite memory. The list case is possible
in theory, but I think it would require a lot of work.
There are other "gotchas" that would come up. For example, I think
the code in the Python generator that creates the type specification
passed to the protocol accelerator module is not recursion-safe.
One workaround you can use is to create something like an inode table
in your struct.
struct Folder {
1: string name;
2: list<i32> subfolders;
}
struct FileSystem {
1: list<Folder> folders;
}
The subfolder integers are indexes into the "folders" list in the
"FileSystem" struct.
--David
Bryan Duxbury wrote:
Up to this point we have avoided it, and it's not on the roadmap.
There have been a few discussions in the past about why we haven't
done this to date.
If someone wanted to tackle this feature, the first thing that would
need to be done is to make the compiler ok with references to structs
that don't appear before them lexically. From there it probably
wouldn't be too much of challenge. Maybe David or someone else with a
deeper sense can chime in?
-Bryan
On Aug 4, 2009, at 9:50 AM, Samir Mulder wrote:
Hi,
I've been using Thrift for over a year now and love it. It has
really increased my productivity in rolling out distributes
services.
But the project I'm working on now needs a feature I haven't needed
before and Thrift does not seem to support it. And that is
recursion in a datatype. The example is that of a folder with
subfolders:
struct Folder
{
1: some data....
2: list<Folder> subfolders
}
The compiler does not allow this since the type 'Folder' is not yet
defined when it reaches the 'subfolders' item.
For this particular project allowing recursion is critical. Google
Protocol Buffers supports it but I don't really want to switch to
that this late in the game.
Any ideas on how to work around this? Is something like this
planned for a future release?
Thanks.
Samir
