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// Copyright (c) 2018 The predicates-rs Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/license/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Definition of `Predicate` for wrapping a `Fn(&T) -> bool`
use std::fmt;
use std::marker::PhantomData;
use crate::reflection;
use crate::utils;
use crate::Predicate;
/// Predicate that wraps a function over a reference that returns a `bool`.
/// This type is returned by the `predicate::function` function.
#[allow(clippy::derive_partial_eq_without_eq)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct FnPredicate<F, T>
where
F: Fn(&T) -> bool,
T: ?Sized,
{
function: F,
name: &'static str,
_phantom: PhantomData<T>,
}
unsafe impl<F, T> Send for FnPredicate<F, T>
where
F: Send + Fn(&T) -> bool,
T: ?Sized,
{
}
unsafe impl<F, T> Sync for FnPredicate<F, T>
where
F: Sync + Fn(&T) -> bool,
T: ?Sized,
{
}
impl<F, T> FnPredicate<F, T>
where
F: Fn(&T) -> bool,
T: ?Sized,
{
/// Provide a descriptive name for this function.
///
/// # Examples
///
/// ```
/// use predicates::prelude::*;
///
/// struct Example {
/// string: String,
/// number: i32,
/// }
///
/// let string_check = predicate::function(|x: &Example| x.string == "hello")
/// .fn_name("is_hello");
/// println!("predicate: {}", string_check);
/// ```
pub fn fn_name(mut self, name: &'static str) -> Self {
self.name = name;
self
}
}
impl<F, T> Predicate<T> for FnPredicate<F, T>
where
F: Fn(&T) -> bool,
T: ?Sized,
{
fn eval(&self, variable: &T) -> bool {
(self.function)(variable)
}
fn find_case<'a>(&'a self, expected: bool, variable: &T) -> Option<reflection::Case<'a>> {
utils::default_find_case(self, expected, variable)
}
}
impl<F, T> reflection::PredicateReflection for FnPredicate<F, T>
where
F: Fn(&T) -> bool,
T: ?Sized,
{
}
impl<F, T> fmt::Display for FnPredicate<F, T>
where
F: Fn(&T) -> bool,
T: ?Sized,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let palette = crate::Palette::new(f.alternate());
write!(
f,
"{}({})",
palette.description(self.name),
palette.var("var"),
)
}
}
/// Creates a new predicate that wraps over the given function. The returned
/// type implements `Predicate` and therefore has all combinators available to
/// it.
///
/// # Examples
///
/// ```
/// use predicates::prelude::*;
///
/// struct Example {
/// string: String,
/// number: i32,
/// }
///
/// let string_check = predicate::function(|x: &Example| x.string == "hello");
/// let number_check = predicate::function(|x: &Example| x.number == 42);
/// let predicate_fn = string_check.and(number_check);
/// let good_example = Example { string: "hello".into(), number: 42 };
/// assert_eq!(true, predicate_fn.eval(&good_example));
/// let bad_example = Example { string: "goodbye".into(), number: 0 };
/// assert_eq!(false, predicate_fn.eval(&bad_example));
/// ```
pub fn function<F, T>(function: F) -> FnPredicate<F, T>
where
F: Fn(&T) -> bool,
T: ?Sized,
{
FnPredicate {
function,
name: "fn",
_phantom: PhantomData,
}
}
#[test]
fn str_function() {
let f = function(|x: &str| x == "hello");
assert!(f.eval("hello"));
assert!(!f.eval("goodbye"));
}