ashtuchkin commented on issue #6326:
URL: https://github.com/apache/arrow-rs/issues/6326#issuecomment-2318037042
That works in simple cases, yes. I've tried this in my slightly more complex
code and then spent unreasonable amount of time trying to make it work.
Specifically, the writer in my case is stateful, so I created a struct with
generic `W: RecordBatchWriter` and needed to specialize it for every format
manually, like this
```rust
struct MyWriter<W: RecordBatchWriter> {
writer: W,
...
}
let writer: Box<dyn MyWriter> = match args.format {
"parquet" =>
Box::new(MyWriter::new(parquet::arrow::ArrowWriter::try_new(file, schema,
None), ...)?),
...
}
use_my_writer_as_part_of_a_pipeline(writer);
```
Now we can't really do that ^^ because MyWriter is not a trait, so we need
to introduce another higher-level trait.
Here's alternative proposal - can we add a `finish(&mut self)` to the trait
to enable dynamic dispatch? We have a [similar semantics in
parquet](https://docs.rs/parquet/52.2.0/parquet/arrow/arrow_writer/struct.ArrowWriter.html#method.finish)
where we have consuming close and non-consuming finish. That should be
backwards compatible and would resolve the difficulties.
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