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% Ergonomic error handling
Error propagation with raw `Result`s can require tedious matching and
repackaging. This tedium is largely alleviated by the `try!` macro,
and can be completely removed (in some cases) by the "`Result`-`impl`"
pattern.
### The `try!` macro
Prefer
```rust
use std::io::{File, Open, Write, IoError};
struct Info {
name: String,
age: i32,
rating: i32
}
fn write_info(info: &Info) -> Result<(), IoError> {
let mut file = File::open_mode(&Path::new("my_best_friends.txt"),
Open, Write);
// Early return on error
try!(file.write_line(&format!("name: {}", info.name)));
try!(file.write_line(&format!("age: {}", info.age)));
try!(file.write_line(&format!("rating: {}", info.rating)));
return Ok(());
}
```
over
```rust
use std::io::{File, Open, Write, IoError};
struct Info {
name: String,
age: i32,
rating: i32
}
fn write_info(info: &Info) -> Result<(), IoError> {
let mut file = File::open_mode(&Path::new("my_best_friends.txt"),
Open, Write);
// Early return on error
match file.write_line(&format!("name: {}", info.name)) {
Ok(_) => (),
Err(e) => return Err(e)
}
match file.write_line(&format!("age: {}", info.age)) {
Ok(_) => (),
Err(e) => return Err(e)
}
return file.write_line(&format!("rating: {}", info.rating));
}
```
See
[the `result` module documentation](http://static.rust-lang.org/doc/master/std/result/index.html#the-try!-macro)
for more details.
### The `Result`-`impl` pattern [FIXME]
> **[FIXME]** Document the way that the `io` module uses trait impls
> on `std::io::Result` to painlessly propagate errors.
|
