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The Default trait is a powerful tool for reducing code repetition and managing complex configurations. When dealing with structs that have many fields, manually specifying every value can be tedious and error-prone. The Default trait, combined with the ..Default::default() syntax, provides an elegant solution to this problem.

Why Use Default?

Consider a scenario where you have a configuration struct with 8 fields, but you only want to customize 1 or 2 of them. Without Default, you would need to write:

let config = AppConfig {
    theme: String::from("Dark"),
    notifications_enabled: true,
    max_users: 100,
    auto_save: true,
    cache_size_mb: 512,
    log_level: String::from("INFO"),
    retry_attempts: 3,
    timeout_seconds: 30,
};

With Default, you can simply write:

let config = AppConfig {
    theme: String::from("Dark"),
    ..Default::default()
};

This not only reduces code repetition but also makes your code more maintainable and less prone to errors.

Your Task

In this challenge, you will implement the Default trait for an AppConfig struct that has several configuration options. The struct should have the following fields and default values:

  • theme (String): Default value "Light"
  • notifications_enabled (bool): Default value true
  • max_users (u32): Default value 100
  • auto_save (bool): Default value true
  • cache_size_mb (u32): Default value 512
  • log_level (String): Default value "INFO"
  • retry_attempts (u32): Default value 3
  • timeout_seconds (u32): Default value 30

Your task is to:

  1. Define the AppConfig struct with all specified fields
  2. Implement the Default trait manually

Hints

<details> <summary>Click here to reveal hints</summary>
  • Use String::from() for string values in the default implementation
  • Remember that ..Default::default() must come last in struct initialization
  • Consider how this pattern would scale with even more configuration options
  • Think about maintainability when default values need to change
</details>
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pub struct AppConfig {
    pub theme: String,
    pub notifications_enabled: bool,
    pub max_users: u32,
}


// TODO: implement the `Default` trait for `AppConfig`


// Example usage
pub fn main() {
    // Create a default configuration
    let default_config = AppConfig::default();
    println!("Default Config: {:?}", default_config);


    // Create a custom configuration using ..Default::default()
    let custom_config = AppConfig {
        theme: String::from("Dark"),
        ..Default::default()
    };
    println!("Custom Config: {:?}", custom_config);
}