validit

Validate variable internal state when the variable is accessed.

• Implement trait Validate for a type T to define how to validate internal state of T.
• Wrapper struct Valid<T: Validate> implements Deref and DerefMut traits, and validates the internal state when the variable is accessed.

For example, If in your program you have a struct Foo(u64) and you want to make sure that a is always less than to 5, you can implement Validate trait for Foo and use less! macro to validate a.

struct Foo(u64);

impl validit::Validate for Foo {
  fn validate(&self) -> Result<(), Box<dyn std::error::Error>> {
    validit::less!(self.0, 5);
    Ok(())
  }
}

fn main() {
  let v1 = Valid::new(Foo(1));
  let _x = v1.0; // Good.

  let v6 = Foo(6);
  let _x = v6.0; // No panic without validation.
  
  let v6 = Valid::new(Foo(6));
  let _x = v6.0; // panic: panicked at 'invalid state: expect: self.0(6) < 5(5) ...
}

Contribution

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