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Clean up Error Handling case study examples #31473

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Feb 10, 2016
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Clean up Error Handling case study examples #31473

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89 changes: 44 additions & 45 deletions src/doc/book/error-handling.md
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Original file line number Diff line number Diff line change
Expand Up @@ -1592,7 +1592,7 @@ fn print_usage(program: &str, opts: Options) {

fn main() {
let args: Vec<String> = env::args().collect();
let program = args[0].clone();
let program = &args[0];

let mut opts = Options::new();
opts.optflag("h", "help", "Show this usage message.");
Expand All @@ -1605,10 +1605,10 @@ fn main() {
print_usage(&program, opts);
return;
}
let data_path = args[1].clone();
let city = args[2].clone();
let data_path = &args[1];
let city = &args[2];

// Do stuff with information
// Do stuff with information
}
```

Expand Down Expand Up @@ -1640,7 +1640,6 @@ sure to add `extern crate csv;` to the top of your file.)

```rust,ignore
use std::fs::File;
use std::path::Path;

// This struct represents the data in each row of the CSV file.
// Type based decoding absolves us of a lot of the nitty gritty error
Expand All @@ -1666,7 +1665,7 @@ fn print_usage(program: &str, opts: Options) {

fn main() {
let args: Vec<String> = env::args().collect();
let program = args[0].clone();
let program = &args[0];

let mut opts = Options::new();
opts.optflag("h", "help", "Show this usage message.");
Expand All @@ -1678,25 +1677,24 @@ fn main() {

if matches.opt_present("h") {
print_usage(&program, opts);
return;
}
return;
}

let data_file = args[1].clone();
let data_path = Path::new(&data_file);
let city = args[2].clone();
let data_path = &args[1];
let city: &str = &args[2];

let file = File::open(data_path).unwrap();
let mut rdr = csv::Reader::from_reader(file);
let file = File::open(data_path).unwrap();
let mut rdr = csv::Reader::from_reader(file);

for row in rdr.decode::<Row>() {
let row = row.unwrap();
for row in rdr.decode::<Row>() {
let row = row.unwrap();

if row.city == city {
println!("{}, {}: {:?}",
row.city, row.country,
row.population.expect("population count"));
}
}
if row.city == city {
println!("{}, {}: {:?}",
row.city, row.country,
row.population.expect("population count"));
}
}
}
```

Expand Down Expand Up @@ -1745,6 +1743,8 @@ Note that we opt to handle the possibility of a missing population count by
simply ignoring that row.

```rust,ignore
use std::path::Path;

struct Row {
// unchanged
}
Expand Down Expand Up @@ -1782,27 +1782,26 @@ fn search<P: AsRef<Path>>(file_path: P, city: &str) -> Vec<PopulationCount> {
}

fn main() {
let args: Vec<String> = env::args().collect();
let program = args[0].clone();
let args: Vec<String> = env::args().collect();
let program = &args[0];

let mut opts = Options::new();
opts.optflag("h", "help", "Show this usage message.");
let mut opts = Options::new();
opts.optflag("h", "help", "Show this usage message.");

let matches = match opts.parse(&args[1..]) {
Ok(m) => { m }
Err(e) => { panic!(e.to_string()) }
};
if matches.opt_present("h") {
print_usage(&program, opts);
return;
}
let matches = match opts.parse(&args[1..]) {
Ok(m) => { m }
Err(e) => { panic!(e.to_string()) }
};
if matches.opt_present("h") {
print_usage(&program, opts);
return;
}

let data_file = args[1].clone();
let data_path = Path::new(&data_file);
let city = args[2].clone();
for pop in search(&data_path, &city) {
println!("{}, {}: {:?}", pop.city, pop.country, pop.count);
}
let data_path = &args[1];
let city = &args[2];
for pop in search(data_path, city) {
println!("{}, {}: {:?}", pop.city, pop.country, pop.count);
}
}

```
Expand Down Expand Up @@ -1912,7 +1911,7 @@ First, here's the new usage:

```rust,ignore
fn print_usage(program: &str, opts: Options) {
println!("{}", opts.usage(&format!("Usage: {} [options] <city>", program)));
println!("{}", opts.usage(&format!("Usage: {} [options] <city>", program)));
}
```
The next part is going to be only a little harder:
Expand All @@ -1924,16 +1923,16 @@ opts.optopt("f", "file", "Choose an input file, instead of using STDIN.", "NAME"
opts.optflag("h", "help", "Show this usage message.");
...
let file = matches.opt_str("f");
let data_file = file.as_ref().map(Path::new);
let data_file = &file.as_ref().map(Path::new);

let city = if !matches.free.is_empty() {
matches.free[0].clone()
&matches.free[0]
} else {
print_usage(&program, opts);
return;
print_usage(&program, opts);
return;
};

match search(&data_file, &city) {
match search(data_file, city) {
Ok(pops) => {
for pop in pops {
println!("{}, {}: {:?}", pop.city, pop.country, pop.count);
Expand Down