Refined-Type

refined-type is a library developed for Rust. It enhances your types, making them more robust and expanding the range of guarantees your applications can statically ensure.

Overview

You can create various rules for a certain type, such as phone numbers, addresses, times, and so on. Once you have established the rules, you can easily combine them. Specifically, if you create rules for 'non-empty strings' and 'strings composed only of alphabets,' you do not need to redefine a new rule for 'non-empty strings composed only of alphabets'. All rules can be arbitrarily combined and extended as long as the target type matches. Enjoy a wonderful type life!

Example Usage

use refined_type::rule::MinMaxU8Rule;
use refined_type::Refined;
use std::ops::Deref;

fn main() {
    let rule = MinMaxU8Rule::new(1, 6).unwrap();

    let five = Refined::new(5, &rule);
    assert_eq!(five.deref(), 5);

    let eight = Refined::new(8, &rule);
    assert!(eight.is_err());
    
    // I have prepared a macro for cases where it would be cumbersome
    // for what is declared at compile time to be returned as a Result type
    let two = refined!(2, &rule);
    assert_eq!(two.deref(), 2);
}

Installation

cargo add refined-type

Custom Rule

There are many situations where you may want to define custom rules. To define rules for a specific target type, you first need to define a struct. In the struct, define fields for specifying detailed conditions. Once the definition is complete, all you need to do is implement the Rule trait. Add your preferred conditions as you like.

use refined_type::rule::Rule;
use refined_type::result::Error;
use refined_type::Refined;

struct BiggerRule {
    than: u32
}

impl BiggerRule {
    pub fn new(than: u32) -> Self {
        Self { than }
    }
}

impl Rule for BiggerRule {
    type Item = u32;
    fn validate(&self, target: Self::Item) -> Result<Self::Item, Error<Self::Item>> {
        if target > self.than {
            Ok(target)
        }
        else {
            Err(Error::new(
                format!("{} is not bigger than {}", target, self.than)
            ))
        }
    }
}

fn main() {
    let bigger_than_five_rule = BiggerRule::new(5);

    let bigger_than_five_result_ok = Refined::new(7, &bigger_than_five_rule);
    let bigger_than_five_result_err = Refined::new(3, &bigger_than_five_rule);

    assert!(bigger_than_five_result_ok.is_ok());
    assert!(bigger_than_five_result_err.is_err());
}

Compose Rules

As mentioned earlier, it is possible to combine any rules as long as the target types match. In the example below, there are standalone rules for 'strings containing Hello' and 'strings containing World'. Since their target type is String, combining them is possible. I have prepared something called Rule Composer (And, Or, Not). By using Rule Composer, composite rules can be easily created.

Original Rules

use refined_type::result::Error;
use refined_type::rule::Rule;
use refined_type::rule::composer::And;
use refined_type::Refined;

struct ContainsHelloRule;
struct ContainsWorldRule;

impl Rule for ContainsHelloRule {
    type Item = String;

    fn validate(&self, target: Self::Item) -> Result<Self::Item, Error<Self::Item>> {
        if target.contains("Hello") {
            Ok(target)
        }
        else {
            Err(Error::new(format!("{} does not contain `Hello`", target)))
        }
    }
}

impl Rule for ContainsWorldRule {
    type Item = String;

    fn validate(&self, target: Self::Item) -> Result<Self::Item, Error<Self::Item>> {
        if target.contains("World") {
            Ok(target)
        }
        else {
            Err(Error::new(format!("{} does not contain `World`", target)))
        }
    }
}

1: And Rule Composer

And Rule Composer is a rule that satisfies both of the two rules. It is generally effective when you want to narrow down the condition range.

fn main() {
    let rule = And::new(ContainsHelloRule, ContainsWorldRule);

    let rule_ok = Refined::new("Hello! World!".to_string(), &rule);
    assert!(rule_ok.is_ok());

    let rule_err = Refined::new("Hello, world!".to_string(), &rule);
    assert!(rule_err.is_err());
}

2: Or Rule Composer

Or Rule Composer is a rule that satisfies either of the two rules. It is generally effective when you want to expand the condition range.

fn main() {
    let rule = Or::new(ContainsHelloRule, ContainsWorldRule);

    let rule_ok_1 = Refined::new("Hello! World!".to_string(), &rule);
    assert!(rule_ok_1.is_ok());

    let rule_ok_2 = Refined::new("hello World!".to_string(), &rule);
    assert!(rule_ok_2.is_ok());

    let rule_err = Refined::new("hello, world!".to_string(), &rule);
    assert!(rule_err.is_err());
}

3: Not Rule Composer

Not Rule Composer is a rule that does not satisfy a specific condition. It is generally effective when you want to discard only certain situations.

fn main() {
    let rule = Not::new(ContainsHelloRule);

    let rule_ok = Refined::new("hello! World!".to_string(), &rule);
    assert!(rule_ok.is_ok());

    let rule_err = Refined::new("Hello, World!".to_string(), &rule);
    assert!(rule_err.is_err());
}

4: Compose Rule Composer

Rule Composer is also a rule. Therefore, it can be treated much like a composite function

fn main() {
    let less_than_3 = LessI8Rule::new(3);
    let more_than_1 = MoreI8Rule::new(1);

    // (1 <= x <= 3)
    let more_than_1_and_less_than_3 = And::new(less_than_3, more_than_1);

    assert!(more_than_1_and_less_than_3.validate(0).is_err());
    assert!(more_than_1_and_less_than_3.validate(2).is_ok());
    assert!(more_than_1_and_less_than_3.validate(4).is_err());

    let more_than_5 = MoreI8Rule::new(5);

    // (1 <= x <= 3) or (5 <= x)
    let or_more_than_5 = Or::new(more_than_1_and_less_than_3, more_than_5);

    assert!(or_more_than_5.validate(0).is_err());
    assert!(or_more_than_5.validate(2).is_ok());
    assert!(or_more_than_5.validate(4).is_err());
    assert!(or_more_than_5.validate(5).is_ok());
    assert!(or_more_than_5.validate(100).is_ok());

    let more_than_7 = MoreI8Rule::new(7);

    // ((1 <= x <= 3) or (5 <= x)) & (x < 7)
    let not_more_than_7 = And::new(or_more_than_5, Not::new(more_than_7));

    assert!(not_more_than_7.validate(0).is_err());
    assert!(not_more_than_7.validate(2).is_ok());
    assert!(not_more_than_7.validate(4).is_err());
    assert!(not_more_than_7.validate(5).is_ok());
    assert!(not_more_than_7.validate(100).is_err());
}

Tips

Directly writing And, Or, Not or Refined can often lead to a decrease in readability. Therefore, using type aliases can help make your code clearer.

type ContainsHelloAndWorldRule = And<String, ContainsHelloRule, ContainsWorldRule>;

type ContainsHelloAndWorld = Refined<ContainsHelloAndWorldRule, String>;

License

MIT License

Copyright (c) 2023 Tomoki Someya

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.