omaha_client/
unless.rs

1// Copyright 2020 The Fuchsia Authors
2//
3// Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
4// <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT
5// license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option.
6// This file may not be copied, modified, or distributed except according to
7// those terms.
8
9//! The Unless trait for a more fluent use of Option::unwrap_or().
10//!
11//! Specificially, this is intended to be used in cases where the "default" value is almost always
12//! the value in use, and the Option is rarely set.
13//!
14//! ```
15//! use omaha_client::unless::Unless;
16//! // This implies that |some_option| is usually set, and "default" is there in case it's not.
17//! let some_option_usually_set = Some("string");
18//! let value = some_option_usually_set.unwrap_or("default");
19//! assert_eq!("string", value);
20//!
21//! // Whereas this implies that "default" is the common case, and |some_option| is an override.
22//! let some_option_usually_unset = None;
23//! let value = "default".unless(some_option_usually_unset);
24//! assert_eq!("default", value);
25//! ```
26
27pub trait Unless: Sized {
28    // unless returns the value of self, unless the option is Some value.
29    //
30    // # Example
31    //
32    // ```
33    // assert_eq!("default", "default".unless(None));
34    // assert_eq!("other", "default".unless(Some("other")));
35    // ```
36    fn unless(self, option: Option<Self>) -> Self;
37}
38
39/// Provide a blanket implementation for all Sized types.
40impl<T: Sized> Unless for T {
41    fn unless(self, option: Option<Self>) -> Self {
42        option.unwrap_or(self)
43    }
44}
45
46#[cfg(test)]
47mod tests {
48    use super::Unless;
49
50    #[test]
51    fn tests() {
52        assert_eq!("default", "default".unless(None));
53        assert_eq!("other", "default".unless(Some("other")));
54    }
55}
omaha_client/unless.rs

omaha_client/
unless.rs
