Crate newstr

Simple macros for declaring String-base new types.

This crate provides simple macros that generate String based new types. The two primary macros implement the validity rules for the new type by either 1) providing a predicate that is used by the is_valid associated function, or 2) providing a function to parse and return a string which is then called by FromStr::from_str.

Both of these methods produce a new type, with the following:

1. An associated predicate function is_valid that returns true if the string provided would be a valid value for the type.
2. This type derives implementations of Clone, Debug, PartialEq, PartialOrd, Eq, Ord, and Hash.
3. An implementation of Display for T that simply returns the inner value.
4. An implementation of From<T> for String.
5. An implementation of Deref for T with the target type str.
6. An implementation of FromStr.

Example

The following example constructs a new string type that implements an Identifier value. This value must be ASCII, alphanumeric, the '_' character and must not be empty.

use std::fmt::{Display, Formatter};
use std::str::FromStr;
use std::ops::Deref;

fn is_identifier_value(s: &str) -> bool {
    !s.is_empty() && s.chars().all(|c| c.is_ascii_alphanumeric() || c == '_')
}

is_valid_newstring!(Identifier, is_identifier_value);

assert!(!Identifier::is_valid(""));
assert!(!Identifier::is_valid("hi!"));
assert!(!Identifier::is_valid("hello world"));
assert!(!Identifier::is_valid("9.99"));

assert_eq!(
    Identifier::from_str("hi").unwrap().to_string(),
    String::from("hi")
);
assert_eq!(
    Identifier::from_str("hello_world").unwrap().to_string(),
    String::from("hello_world")
);

Dependencies

In the example above you can see the necessary use-statements for the trait implementations the macros generate. Unless you use regex_is_valid there are no crate dependencies; if you do you will need to add lazy_static and regex dependencies.

If the macros in this crate take on addition dependencies or provide new implementations the set of use statements may change which will break consumer builds. To avoid this another macro, use_required, will add any required use statements the consumer requires.

# use newstr::{is_valid_newstring, use_required};
use_required!();

is_valid_newstring!(NotEmpty, |s: &str| !s.is_empty());

Changes

Version 0.1.1

• Added new use_required macro.
• Removed unnecessary feature 'regex_is_valid', the build doesn't require this to avoid bloat.
• Made lazy_static and regex dev dependencies, if you don't use them, you don't need them.
• Added dependency on cargo-husky for Git cleanliness.

Version 0.1.0

• Initial version.