#[macro_use]
extern crate derive_builder;
#[derive(Builder, Debug, PartialEq)]
#[builder(build_fn(validate="Self::validate"))]
struct Lorem {
pub ipsum: u8,
}
impl LoremBuilder {
fn validate(&self) -> Result<(), String> {
if let Some(ref ipsum) = self.ipsum {
match *ipsum {
i if i < 20 => Err("Try harder".to_string()),
i if i > 100 => Err("You'll tire yourself out".to_string()),
_ => Ok(()),
}
} else {
Ok(())
}
}
}
fn main() {
let x = LoremBuilder::default().ipsum(120).build().unwrap_err();
assert_eq!(&x, "You'll tire yourself out");
}