Thanks for the quick response, Steven! Having done what you suggested, I'm
now getting the following error (for serializing a larger struct in which
some fields are strings):
impl<T: Writer> MySerialization for T {
fn write_my_string(&mut self, s: &str) -> IoResult<()> {
...
}
}
impl StructToBeSerialized {
fn save_to(&self, writer: &mut io::Writer) -> io::IoResult<()> {
try!(writer.write_my_string(self.string_field_1)); // error at this line
}
}
The error is at the indicated line and it says: cannot borrow immutable
argument `writer` as mutable. However, the function argument writer to
save_to is a &mut io::Writer, which would seem to be mutable to me. Would
you happen to know what's going wrong with this code?
Thanks again!
Frank
On Sat, Apr 5, 2014 at 1:17 PM, Steven Fackler <sfack...@gmail.com> wrote:
> 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
>>
>> _______________________________________________
>> Rust-dev mailing list
>> Rust-dev@mozilla.org
>> https://mail.mozilla.org/listinfo/rust-dev
>>
>>
>
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