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//! This example shows using custom validation with a non-string error type.
//!
//! This relies on how the generated build function is constructed; the validator
//! is invoked in conjunction with the `?` operator, so anything that converts to
//! the generated `FooBuilderError` type is valid.
#![allow(dead_code)]
#[macro_use]
extern crate derive_builder;
use derive_builder::UninitializedFieldError;
use std::fmt;
fn validate_age(builder: &ExampleBuilder) -> Result<(), Error> {
match builder.age {
Some(age) if age > 150 => Err(Error::UnrealisticAge(age)),
_ => Ok(()),
}
}
#[derive(Debug, Builder)]
#[builder(setter(into), build_fn(validate = "validate_age", error = "Error"))]
struct Example {
name: String,
age: usize,
}
enum Error {
UninitializedField(&'static str),
UnrealisticAge(usize),
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
Self::UnrealisticAge(age) => write!(f, "Nobody is {} years old", age),
Self::UninitializedField(field) => write!(f, "Required field '{}' not set", field),
}
}
}
impl From<UninitializedFieldError> for Error {
fn from(e: UninitializedFieldError) -> Self {
Self::UninitializedField(e.field_name())
}
}
fn main() {
let person_err = ExampleBuilder::default()
.name("Jane Doe")
.age(200usize)
.build()
.unwrap_err();
println!("{}", person_err);
}
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