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//! # Strum //! //! [![Build Status](https://travis-ci.org/Peternator7/strum.svg?branch=master)](https://travis-ci.org/Peternator7/strum) //! [![Latest Version](https://img.shields.io/crates/v/strum.svg)](https://crates.io/crates/strum) //! [![Rust Documentation](https://docs.rs/strum/badge.svg)](https://docs.rs/strum) //! //! Strum is a set of macros and traits for working with //! enums and strings easier in Rust. //! //! # Including Strum in Your Project //! //! Import strum and strum_macros into your project by adding the following lines to your //! Cargo.toml. Strum_macros contains the macros needed to derive all the traits in Strum. //! //! ```toml //! [dependencies] //! strum = "0.11.0" //! strum_macros = "0.11.0" //! ``` //! //! And add these lines to the root of your project, either lib.rs or main.rs. //! //! ```rust //! // Strum contains all the trait definitions //! extern crate strum; //! #[macro_use] //! extern crate strum_macros; //! # fn main() {} //! ``` //! //! # Strum Macros //! //! Strum has implemented the following macros: //! //! 1. `EnumString`: auto-derives `std::str::FromStr` on the enum. Each variant of the enum will match on it's //! own name. This can be overridden using `serialize="DifferentName"` or `to_string="DifferentName"`on the attribute as shown below. //! Multiple deserializations can be added to the same variant. If the variant contains additional data, //! they will be set to their default values upon deserialization. //! //! The `default` attribute can be applied to a tuple variant with a single data parameter. When a match isn't //! found, the given variant will be returned and the input string will be captured in the parameter. //! //! Here is an example of the code generated by deriving `EnumString`. //! //! ``` //! # extern crate strum; //! # #[macro_use] extern crate strum_macros; //! #[derive(EnumString)] //! enum Color { //! Red, //! //! // The Default value will be inserted into range if we match "Green". //! Green { range:usize }, //! //! // We can match on multiple different patterns. //! #[strum(serialize="blue",serialize="b")] //! Blue(usize), //! //! // Notice that we can disable certain variants from being found //! #[strum(disabled="true")] //! Yellow, //! } //! //! /* //! //The generated code will look like: //! impl ::std::str::FromStr for Color { //! type Err = ::strum::ParseError; //! //! fn from_str(s: &str) -> ::std::result::Result<Color, Self::Err> { //! match s { //! "Red" => ::std::result::Result::Ok(Color::Red), //! "Green" => ::std::result::Result::Ok(Color::Green { range:Default::default() }), //! "blue" | "b" => ::std::result::Result::Ok(Color::Blue(Default::default())), //! _ => ::std::result::Result::Err(strum::ParseError::VariantNotFound), //! } //! } //! } //! */ //! # fn main() {} //! ``` //! //! Note that the implementation of `FromStr` by default only matches on the name of the //! variant. There is an option to match on different case conversions through the //! `#[strum(serialize_all = "snake_case")]` type attribute. See the **Additional Attributes** //! Section for more information on using this feature. //! //! 2. `Display`, `ToString`: both derives print out the given enum variant. This enables you to perform round trip //! style conversions from enum into string and back again for unit style variants. `ToString` and `Display` //! choose which serialization to used based on the following criteria: //! //! 1. If there is a `to_string` property, this value will be used. There can only be one per variant. //! 2. Of the various `serialize` properties, the value with the longest length is chosen. If that //! behavior isn't desired, you should use `to_string`. //! 3. The name of the variant will be used if there are no `serialize` or `to_string` attributes. //! //! **`Display` should be preferred to `ToString`. All types that implement `::std::fmt::Display` have a default `ToString` implementation.** //! //! ```rust //! # extern crate strum; //! # #[macro_use] extern crate strum_macros; //! // You need to bring the type into scope to use it!!! //! use std::string::ToString; //! //! #[derive(Display, Debug)] //! enum Color { //! #[strum(serialize="redred")] //! Red, //! Green { range:usize }, //! Blue(usize), //! Yellow, //! } //! //! // It's simple to iterate over the variants of an enum. //! fn debug_colors() { //! let red = Color::Red; //! assert_eq!(String::from("redred"), red.to_string()); //! } //! //! fn main () { debug_colors(); } //! ``` //! //! 3. `AsRefStr`: this derive implements `AsRef<str>` on your enum using the same rules as //! `ToString` for determining what string is returned. The difference is that `as_ref()` returns //! a borrowed `str` instead of a `String` so you can save an allocation. //! //! 4. `AsStaticStr`: this is similar to `AsRefStr`, but returns a `'static` reference to a string which is helpful //! in some scenarios. This macro implements `strum::AsStaticRef<str>` which adds a method `.as_static()` that //! returns a `&'static str`. //! //! ```rust //! # extern crate strum; //! # #[macro_use] extern crate strum_macros; //! use strum::AsStaticRef; //! //! #[derive(AsStaticStr)] //! enum State<'a> { //! Initial(&'a str), //! Finished //! } //! //! fn print_state<'a>(s:&'a str) { //! let state = State::Initial(s); //! // The following won't work because the lifetime is incorrect so we can use.as_static() instead. //! // let wrong: &'static str = state.as_ref(); //! let right: &'static str = state.as_static(); //! println!("{}", right); //! } //! //! fn main() { //! print_state(&"hello world".to_string()) //! } //! ``` //! //! 4. `EnumIter`: iterate over the variants of an Enum. Any additional data on your variants will be //! set to `Default::default()`. The macro implements `strum::IntoEnumIter` on your enum and //! creates a new type called `YourEnumIter` that implements both `Iterator` and `ExactSizeIterator`. //! You cannot derive `EnumIter` on any type with a lifetime bound (`<'a>`) because the iterator would surely //! create [unbounded lifetimes] (https://doc.rust-lang.org/nightly/nomicon/unbounded-lifetimes.html). //! //! ```rust //! # extern crate strum; //! # #[macro_use] extern crate strum_macros; //! # use std::fmt::Debug; //! // You need to bring the type into scope to use it!!! //! use strum::IntoEnumIterator; //! //! #[derive(EnumIter,Debug)] //! enum Color { //! Red, //! Green { range:usize }, //! Blue(usize), //! Yellow, //! } //! //! // It's simple to iterate over the variants of an enum. //! fn debug_colors() { //! for color in Color::iter() { //! println!("My favorite color is {:?}", color); //! } //! } //! //! fn main() { //! debug_colors(); //! } //! ``` //! //! 5. `EnumMessage`: encode strings into the enum itself. This macro implements //! the `strum::EnumMessage` trait. `EnumMessage` looks for //! `#[strum(message="...")]` attributes on your variants. //! You can also provided a `detailed_message="..."` attribute to create a //! seperate more detailed message than the first. //! //! The generated code will look something like: //! //! ```rust //! # extern crate strum; //! # #[macro_use] extern crate strum_macros; //! // You need to bring the type into scope to use it!!! //! use strum::EnumMessage; //! //! #[derive(EnumMessage,Debug)] //! enum Color { //! #[strum(message="Red",detailed_message="This is very red")] //! Red, //! #[strum(message="Simply Green")] //! Green { range:usize }, //! #[strum(serialize="b",serialize="blue")] //! Blue(usize), //! } //! //! /* //! // Generated code //! impl ::strum::EnumMessage for Color { //! fn get_message(&self) -> ::std::option::Option<&str> { //! match self { //! &Color::Red => ::std::option::Option::Some("Red"), //! &Color::Green {..} => ::std::option::Option::Some("Simply Green"), //! _ => None //! } //! } //! //! fn get_detailed_message(&self) -> ::std::option::Option<&str> { //! match self { //! &Color::Red => ::std::option::Option::Some("This is very red"), //! &Color::Green {..}=> ::std::option::Option::Some("Simply Green"), //! _ => None //! } //! } //! //! fn get_serializations(&self) -> &[&str] { //! match self { //! &Color::Red => { //! static ARR: [&'static str; 1] = ["Red"]; //! &ARR //! }, //! &Color::Green {..}=> { //! static ARR: [&'static str; 1] = ["Green"]; //! &ARR //! }, //! &Color::Blue (..) => { //! static ARR: [&'static str; 2] = ["b", "blue"]; //! &ARR //! }, //! } //! } //! } //! */ //! # fn main() {} //! ``` //! //! 6. `EnumProperty`: Enables the encoding of arbitary constants into enum variants. This method //! currently only supports adding additional string values. Other types of literals are still //! experimental in the rustc compiler. The generated code works by nesting match statements. //! The first match statement matches on the type of the enum, and the inner match statement //! matches on the name of the property requested. This design works well for enums with a small //! number of variants and properties, but scales linearly with the number of variants so may not //! be the best choice in all situations. //! //! Here's an example: //! //! ```rust //! # extern crate strum; //! # #[macro_use] extern crate strum_macros; //! # use std::fmt::Debug; //! // You need to bring the type into scope to use it!!! //! use strum::EnumProperty; //! //! #[derive(EnumProperty,Debug)] //! enum Color { //! #[strum(props(Red="255",Blue="255",Green="255"))] //! White, //! #[strum(props(Red="0",Blue="0",Green="0"))] //! Black, //! #[strum(props(Red="0",Blue="255",Green="0"))] //! Blue, //! #[strum(props(Red="255",Blue="0",Green="0"))] //! Red, //! #[strum(props(Red="0",Blue="0",Green="255"))] //! Green, //! } //! //! fn main() { //! let my_color = Color::Red; //! let display = format!("My color is {:?}. It's RGB is {},{},{}", my_color //! , my_color.get_str("Red").unwrap() //! , my_color.get_str("Green").unwrap() //! , my_color.get_str("Blue").unwrap()); //! # let expected = String::from("My color is Red. It's RGB is 255,0,0"); //! # assert_eq!(expected, display); //! } //! ``` //! //! 7. `EnumDiscriminants`: Given an enum named `MyEnum`, generates another enum called //! `MyEnumDiscriminants` with the same variants, without any data fields. This is useful when you //! wish to determine the variant of an enum from a String, but the variants contain any //! non-`Default` fields. By default, the generated enum has the following derives: //! `Clone, Copy, Debug, PartialEq, Eq`. You can add additional derives using the //! `#[strum_discriminants(derive(AdditionalDerive))]` attribute. //! //! Here's an example: //! //! ```rust //! # extern crate strum; //! # #[macro_use] extern crate strum_macros; //! //! // Bring trait into scope //! use std::str::FromStr; //! //! #[derive(Debug)] //! struct NonDefault; //! //! #[allow(dead_code)] //! #[derive(Debug, EnumDiscriminants)] //! #[strum_discriminants(derive(EnumString))] //! enum MyEnum { //! Variant0(NonDefault), //! Variant1 { a: NonDefault }, //! } //! //! fn main() { //! assert_eq!( //! MyEnumDiscriminants::Variant0, //! MyEnumDiscriminants::from_str("Variant0").unwrap() //! ); //! } //! ``` //! //! You can also rename the generated enum using the `#[strum_discriminants(name(OtherName))]` //! attribute: //! //! ```rust //! # extern crate strum; //! # #[macro_use] extern crate strum_macros; //! // You need to bring the type into scope to use it!!! //! use strum::IntoEnumIterator; //! //! #[allow(dead_code)] //! #[derive(Debug, EnumDiscriminants)] //! #[strum_discriminants(name(MyVariants), derive(EnumIter))] //! enum MyEnum { //! Variant0(bool), //! Variant1 { a: bool }, //! } //! //! fn main() { //! assert_eq!( //! vec![MyVariants::Variant0, MyVariants::Variant1], //! MyVariants::iter().collect::<Vec<_>>() //! ); //! } //! ``` //! //! The derived enum also has the following trait implementations: //! //! * `impl From<MyEnum> for MyEnumDiscriminants` //! * `impl<'_enum> From<&'_enum MyEnum> for MyEnumDiscriminants` //! //! These allow you to get the *Discriminants* enum variant from the original enum: //! //! ```rust //! extern crate strum; //! #[macro_use] extern crate strum_macros; //! //! #[derive(Debug, EnumDiscriminants)] //! #[strum_discriminants(name(MyVariants))] //! enum MyEnum { //! Variant0(bool), //! Variant1 { a: bool }, //! } //! //! fn main() { //! assert_eq!(MyVariants::Variant0, MyEnum::Variant0(true).into()); //! } //! ``` //! //! # Additional Attributes //! //! Strum supports several custom attributes to modify the generated code. At the enum level, the //! `#[strum(serialize_all = "snake_case")]` attribute can be used to change the case used when //! serializing to and deserializing from strings: //! //! ```rust //! extern crate strum; //! #[macro_use] //! extern crate strum_macros; //! //! #[derive(Debug, Eq, PartialEq, ToString)] //! #[strum(serialize_all = "snake_case")] //! enum Brightness { //! DarkBlack, //! Dim { //! glow: usize, //! }, //! #[strum(serialize = "bright")] //! BrightWhite, //! } //! //! fn main() { //! assert_eq!( //! String::from("dark_black"), //! Brightness::DarkBlack.to_string().as_ref() //! ); //! assert_eq!( //! String::from("dim"), //! Brightness::Dim { glow: 0 }.to_string().as_ref() //! ); //! assert_eq!( //! String::from("bright"), //! Brightness::BrightWhite.to_string().as_ref() //! ); //! } //! ``` //! //! Custom attributes are applied to a variant by adding `#[strum(parameter="value")]` to the variant. //! //! - `serialize="..."`: Changes the text that `FromStr()` looks for when parsing a string. This attribute can //! be applied multiple times to an element and the enum variant will be parsed if any of them match. //! //! - `default="true"`: Applied to a single variant of an enum. The variant must be a Tuple-like //! variant with a single piece of data that can be create from a `&str` i.e. `T: From<&str>`. //! The generated code will now return the variant with the input string captured as shown below //! instead of failing. //! //! ```ignore //! // Replaces this: //! _ => Err(strum::ParseError::VariantNotFound) //! // With this in generated code: //! default => Ok(Variant(default.into())) //! ``` //! The plugin will fail if the data doesn't implement From<&str>. You can only have one `default` //! on your enum. //! //! - `disabled="true"`: removes variant from generated code. //! //! - `message=".."`: Adds a message to enum variant. This is used in conjunction with the `EnumMessage` //! trait to associate a message with a variant. If `detailed_message` is not provided, //! then `message` will also be returned when get_detailed_message() is called. //! //! - `detailed_message=".."`: Adds a more detailed message to a variant. If this value is omitted, then //! `message` will be used in it's place. //! //! - `props(key="value")`: Used by EnumProperty to add additional information to an enum variant. Multiple //! properties can be added in a single nested block. //! //! # Examples //! //! Using `EnumMessage` for quickly implementing `Error` //! //! ```rust //! extern crate strum; //! #[macro_use] //! extern crate strum_macros; //! # use std::error::Error; //! # use std::fmt::*; //! use strum::EnumMessage; //! //! #[derive(Debug, EnumMessage)] //! enum ServerError { //! #[strum(message="A network error occured")] //! #[strum(detailed_message="Try checking your connection.")] //! NetworkError, //! #[strum(message="User input error.")] //! #[strum(detailed_message="There was an error parsing user input. Please try again.")] //! InvalidUserInputError, //! } //! //! impl Display for ServerError { //! fn fmt(&self, f: &mut Formatter) -> Result { //! write!(f, "{}", self.get_message().unwrap()) //! } //! } //! //! impl Error for ServerError { //! fn description(&self) -> &str { //! self.get_detailed_message().unwrap() //! } //! } //! # fn main() {} //! ``` //! //! Using `EnumString` to tokenize a series of inputs: //! //! ```rust //! extern crate strum; //! #[macro_use] //! extern crate strum_macros; //! use std::str::FromStr; //! //! #[derive(Eq, PartialEq, Debug, EnumString)] //! enum Tokens { //! #[strum(serialize="fn")] //! Function, //! #[strum(serialize="(")] //! OpenParen, //! #[strum(serialize=")")] //! CloseParen, //! #[strum(default="true")] //! Ident(String) //! } //! //! fn main() { //! let toks = ["fn", "hello_world", "(", ")"].iter() //! .map(|tok| Tokens::from_str(tok).unwrap()) //! .collect::<Vec<_>>(); //! //! assert_eq!(toks, vec![Tokens::Function, //! Tokens::Ident(String::from("hello_world")), //! Tokens::OpenParen, //! Tokens::CloseParen]); //! } //! ``` //! //! # Debugging //! //! To see the generated code, set the STRUM_DEBUG environment variable before compiling your code. //! `STRUM_DEBUG=1` will dump all of the generated code for every type. `STRUM_DEBUG=YourType` will //! only dump the code generated on a type named YourType. //! /// The ParseError enum is a collection of all the possible reasons /// an enum can fail to parse from a string. #[derive(Debug, Clone, Copy, Eq, PartialEq, Hash)] pub enum ParseError { VariantNotFound, } impl std::fmt::Display for ParseError { fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> { // We could use our macro here, but this way we don't take a dependency on the // macros crate. match self { &ParseError::VariantNotFound => write!(f, "Matching variant not found"), } } } impl std::error::Error for ParseError { fn description(&self) -> &str { match self { &ParseError::VariantNotFound => { "Unable to find a variant of the given enum matching the string given. Matching \ can be extended with the Serialize attribute and is case sensitive." } } } } /// This trait designates that an `Enum` can be iterated over. It can /// be auto generated using `strum_macros` on your behalf. /// /// # Example /// /// ```rust /// # extern crate strum; /// # #[macro_use] extern crate strum_macros; /// # use std::fmt::Debug; /// // You need to bring the type into scope to use it!!! /// use strum::IntoEnumIterator; /// /// #[derive(EnumIter,Debug)] /// enum Color { /// Red, /// Green { range:usize }, /// Blue(usize), /// Yellow, /// } /// /// // Iterating over any enum requires 2 type parameters /// // A 3rd is used in this example to allow passing a predicate /// fn generic_iterator<E, I, F>(pred: F) /// where E: IntoEnumIterator<Iterator=I>, /// I: Iterator<Item=E>, /// F: Fn(E) { /// for e in E::iter() { /// pred(e) /// } /// } /// /// fn main() { /// generic_iterator::<Color,_, _>(|color| println!("{:?}", color)); /// } /// ``` pub trait IntoEnumIterator { type Iterator; fn iter() -> Self::Iterator; } /// Associates additional pieces of information with an Enum. This can be /// autoimplemented by deriving `EnumMessage` and annotating your variants with /// `#[strum(message="...")]. /// /// # Example /// /// ```rust /// # extern crate strum; /// # #[macro_use] extern crate strum_macros; /// # use std::fmt::Debug; /// // You need to bring the type into scope to use it!!! /// use strum::EnumMessage; /// /// #[derive(PartialEq, Eq, Debug, EnumMessage)] /// enum Pet { /// #[strum(message="I have a dog")] /// #[strum(detailed_message="My dog's name is Spots")] /// Dog, /// #[strum(message="I don't have a cat")] /// Cat, /// } /// /// fn main() { /// let my_pet = Pet::Dog; /// assert_eq!("I have a dog", my_pet.get_message().unwrap()); /// } /// ``` pub trait EnumMessage { fn get_message(&self) -> Option<&str>; fn get_detailed_message(&self) -> Option<&str>; fn get_serializations(&self) -> &[&str]; } /// EnumProperty is a trait that makes it possible to store additional information /// with enum variants. This trait is designed to be used with the macro of the same /// name in the `strum_macros` crate. Currently, the only string literals are supported /// in attributes, the other methods will be implemented as additional attribute types /// become stabilized. /// /// # Example /// /// ```rust /// # extern crate strum; /// # #[macro_use] extern crate strum_macros; /// # use std::fmt::Debug; /// // You need to bring the type into scope to use it!!! /// use strum::EnumProperty; /// /// #[derive(PartialEq, Eq, Debug, EnumProperty)] /// enum Class { /// #[strum(props(Teacher="Ms.Frizzle", Room="201"))] /// History, /// #[strum(props(Teacher="Mr.Smith"))] /// #[strum(props(Room="103"))] /// Mathematics, /// #[strum(props(Time="2:30"))] /// Science, /// } /// /// fn main() { /// let history = Class::History; /// assert_eq!("Ms.Frizzle", history.get_str("Teacher").unwrap()); /// } /// ``` pub trait EnumProperty { fn get_str(&self, &str) -> Option<&'static str>; fn get_int(&self, &str) -> Option<usize> { Option::None } fn get_bool(&self, &str) -> Option<bool> { Option::None } } /// A cheap reference-to-reference conversion. Used to convert a value to a /// reference value with `'static` lifetime within generic code. pub trait AsStaticRef<T> where T: ?Sized, { fn as_static(&self) -> &'static T; }