enum-methods

Enum getter/is_XXX method generation.

crates.io

docs.rs

Usage

In your Cargo.toml, add this line under your [dependencies] section:

enum-methods = "0.0.3"

To use, simply derive and call methods (see the example below).

Why?

Usually when you write an enum with one or zero values, you might want to add a set of getters for them. As such:

#[derive(Debug)]
enum MyEnum {
    Foo(i64),
    Bar(char),
    Baz(String),
}

impl MyEnum {
    pub fn foo(&self) -> i64 {
        if let &MyEnum::Foo(i) = self {
            i
        }
        else {
            panic!("called MyEnum::Foo() on {:?}", self)
        }
    }
    // et cetera
}

But this gets tedious, and adds a lot code for this simple functionality. Enter enum-methods.

Instead of doing the above with the if let ... else { panic!(...) }, you simply derive from the EnumGetters

#[macro_use]
extern crate enum_methods;

#[derive(EnumGetters, Debug)]
enum MyEnum {
    Foo(i64),
    Bar(char),
    Baz(String),
}

fn main() {
    let foo = MyEnum::Foo(42);
    assert_eq!(foo.foo(), 42);  // success!
}

Requirements and gotchas

Right now, enum-methods has only two derivable options:

• EnumGetters
• EnumIsA

EnumGetters has a couple of limitations.

• Any enum variant which has exactly 1 member will have a getter generated for it. All other variants are ignored.
• Generated methods simply use the lower-case version of their variant name. These names are not converated to snake_case. see #1.
• Enums which derive from EnumGetters must also derive from Debug - this is for when a method is called for the wrong variant and needs to panic!.

EnumIsA is much simpler than the previous; it simply adds is_XXX methods returning a boolean for whether the variant matches or not. Similar to EnumGetters, the name is converted to lowercase and does not convert to snake_case.

License

This software is released under the Apache license 2.0. See the LICENSE file for more details.