15.7 Best Practices

15.7.1 Returning Errors to the Call Site

It's often better to return errors to the call site rather than handling them immediately within a function. This approach:

  • Provides Flexibility: Allows the caller to decide how to handle the error, whether to retry, log, or propagate it further.
  • Simplifies Functions: Keeps functions focused on their primary task without being cluttered with error-handling logic.
  • Encourages Reusability: Functions that return Result can be reused in different contexts with varying error-handling strategies.

Example:

use std::io;
fn read_config_file() -> Result<Config, io::Error> {
    let contents = std::fs::read_to_string("config.toml")?;
    parse_config(&contents)
}
fn main() {
    // Ensure all possible error cases are handled, providing meaningful responses or recovery strategies.
    match read_config_file() {
        Ok(config) => apply_config(config),
        Err(e) => {
            eprintln!("Failed to read config: {}", e);
            // Decide how to handle the error here
            apply_default_config();
        }
    }
}

15.7.2 Meaningful Error Messages

Provide clear and informative error messages to aid in debugging and user understanding.

Example:

fn read_file(path: &str) -> Result<String, String> {
    std::fs::read_to_string(path)
        .map_err(|e| format!("Error reading {}: {}", path, e))
}

15.7.3 Cautious Use of unwrap and expect

Avoid using unwrap and expect unless you are certain that a value is present.

  • Risky:

    let content = std::fs::read_to_string("config.toml").unwrap();

  • Safer Alternative:

    let content = std::fs::read_to_string("config.toml")
    .expect("Failed to read config.toml. Please ensure the file exists.");

  • Best Practice:

    match std::fs::read_to_string("config.toml") {
    Ok(content) => {
        // Use content
    }
    Err(e) => eprintln!("Error: {}", e),


}

By handling errors explicitly, you enhance program stability and user experience.