This crate is based around two derive macros, Buildable and Generatable which provide a method to construct a Builder and Generator respectively for your type, wrapping up a lot of boilerplate within them.

Builder

A Builder is a way to create a single object, specifying only the fields you wish to give non-default values. The default values are specified using attributes on your type for ease of reading. Each field gains a method of the same type in the builder which can be be used to customise it.

Example

use boulder::{Builder, Buildable};
#[derive(Buildable)]
struct Foo {
#[boulder(default=5)]
pub a: i32,
#[boulder(default="hello")]
pub b: String,
}

let f = Foo::builder()
.a(27)
.build();
assert_eq!(f.a, 27);
assert_eq!(f.b, "hello".to_string());

Generator

A Generator is a way to create an infinite sequence of objects, again specifying only the function for generating the fields you wish to have non-default sequences. The default sequences are specified using attributes on your type for ease of reading. Each field gains a method of the same type in the generator which can be be used to customise the sequence of values it takes between objects.

Example

use boulder::{gen, Generator, Generatable};
#[derive(Generatable)]
struct Bar {
#[boulder(generator=gen::Inc(1i32))]
pub a: i32,
#[boulder(generator=gen::Pattern!("hello-{}-foo", gen::Inc(5i32)))]
pub b: String,
}

let mut n = 2;
let mut gen = Bar::generator();
gen.a(move || {
n = n + 2;
n
});

let bar1 = gen.generate();
assert_eq!(bar1.a, 4);
assert_eq!(bar1.b, "hello-5-foo".to_string());

let bar2 = gen.generate();
assert_eq!(bar2.a, 6);
assert_eq!(bar2.b, "hello-6-foo".to_string());