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In Rust, methods and associated functions are both defined using impl blocks. While they are similar in some ways, they serve different purposes:

  1. Associated Functions:

    • Defined without a self parameter.
    • Typically used as constructors or utility functions.
    • Called using the struct's name, e.g., StructName::function_name().

  2. Methods:

    • Defined with a self parameter (&self, &mut self, or self).
    • Operate on an instance of the struct.
    • Called on a struct instance using the dot syntax, e.g., instance.method_name().

In the previous challenge, the Logger::log_message was an associated function because it didn't take self as a parameter. In this challenge, you will learn how to create methods that operate on struct instances.

Your Task

Define a struct Counter that represents a simple counter. Implement methods on this struct to increment, decrement, and get the current count. This will help you understand how to define and use methods that operate on a struct instance.

Requirements

  1. Define a struct Counter with a single field count of type i32.

  2. Define a new associated function that acts as a constructor and initializes the count field to 0.

  3. Implement the following methods for Counter:

    • increment: Increments the counter by 1.
    • decrement: Decrements the counter by 1.
    • get_count: Returns the current count.

  4. Ensure these methods use the correct self parameter type (&self or &mut self) based on their behavior.

  5. Make the count field private and provide a public constructor Counter::new that initializes the count to 0.

Example Test

let mut counter = Counter::new();
counter.increment();
counter.increment();
assert_eq!(counter.get_count(), 2);


counter.decrement();
assert_eq!(counter.get_count(), 1);

Hints

If you're stuck, you can check out these hints:

<details> <summary>Click here to reveal hints</summary>
  • Fort he increment and decrement methods, use &mut self as the parameter type.
  • Use self.count += 1 to modify the counter in the increment method.
  • Use self.count -= 1 to modify the counter in the decrement method.
  • For get_count, use &self and return the value of self.count.
</details>
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// 1. Define the struct
pub struct Counter




// 2. Implement the associated function and methods




// Example use case
pub fn main() {
    let mut counter = Counter::new();


    counter.increment();
    assert_eq!(counter.get_count(), 1);


    counter.increment();
    counter.increment();
    assert_eq!(counter.get_count(), 3);


    counter.decrement();
    assert_eq!(counter.get_count(), 2);


    counter.decrement();
    counter.decrement();
    assert_eq!(counter.get_count(), 0);
}