You can do it like this:
impl<T: Writer> MySerialization for T {
...
}
Steven Fackler
On Sat, Apr 5, 2014 at 12:57 PM, Frank Huang <m...@nongraphical.com> wrote:
> Hello everyone,
>
> I have a question about making "extension methods" on something like
> io::Writer. Basically, I have a data format that requires strings to be
> serialized as an 8-byte length header and then the string bytes themselves.
> Instead of having to type writer.write_u64(...); writer.write_str(...);
> over and over again, I would like to implement some "extension methods" or
> something like that on io::Writer, like the following pseudocode:
>
> trait MySerialization {
> fn write_my_string(&mut self, s: &str) -> io::IoResult<()>;
> }
>
> impl MySerialization for io::Writer {
> fn write_my_string(&mut self, s: &str) -> io::IoResult<()> {
> try!(self.write_u64(s.len());
> self.write_str(s);
> }
> }
>
> However, this of course doesn't work, because I can't implement a trait
> for a trait. Rustc says: "reference to trait `io::Writer` where a type is
> expected; try `@io::Writer`, `~io::Writer`, or `&io::Writer`", however when
> I try "&io::Writer" as suggested, rustc complains about lifetimes. Is this
> sort of thing possible in Rust?
>
> Thanks for your help!
> - Frank
>
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>
>
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