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// Copyright 2017 Ulrich Rhein // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. //! The `string-error` crate. //! //! This crate provides a simple way to use a string as an error //! trait object, i.e. `Box<std::error::Error>`. //! //! If you need more sophisticated error handling, you should consider //! [error-chain](https://crates.io/crates/error-chain), which also provides //! functionality to create simple errors from Strings. use std::fmt; use std::error::Error; /// Wraps `&'static str` and implements the `Error` trait for it. #[derive(Debug)] struct StaticStrError { error: &'static str } impl Error for StaticStrError { fn description(&self) -> &str { self.error } } impl fmt::Display for StaticStrError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.write_str(self.error) } } /// Wraps an owned `String` and implements the `Error` trait for it. #[derive(Debug)] struct StringError { error: String } impl Error for StringError { fn description(&self) -> &str { &self.error } } impl fmt::Display for StringError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "Error: {}", self.error) } } /// Creates an error trait object for a string constant (`&'static str`). /// /// # Examples /// /// ``` /// use string_error::*; /// /// let x = static_err("Foo"); /// assert_eq!(x.description(), "Foo"); /// ``` pub fn static_err(e: &'static str) -> Box<Error> { Box::new(StaticStrError { error: e }) } /// Creates an error trait object for a string (`&str`). /// /// This copies the argument into an owned string. To avoid the copy, use /// either `into_err` or `static_err`. /// /// # Examples /// /// ``` /// use string_error::*; /// /// let x = new_err("Foo"); /// assert_eq!(x.description(), "Foo"); /// ``` pub fn new_err(e: &str) -> Box<Error> { Box::new(StringError { error: String::from(e) }) } /// Creates an error trait object for an owned string (`String`). /// /// This takes ownership of the `String` argument. /// /// # Examples /// /// ``` /// use string_error::*; /// /// let x = into_err(String::from("Foo")); /// assert_eq!(x.description(), "Foo"); /// ``` pub fn into_err(e: String) -> Box<Error> { Box::new(StringError { error: e }) } #[cfg(test)] mod tests { use super::*; static SOME_STRING : &'static str = "This is a String?!"; #[test] fn test_static_err() { let x = static_err(SOME_STRING); assert_eq!(x.description(), SOME_STRING); assert!(x.cause().is_none()); } #[test] fn test_new_err() { let x = new_err(SOME_STRING); assert_eq!(x.description(), SOME_STRING); assert!(x.cause().is_none()); } #[test] fn test_into_err() { let x = into_err(String::from(SOME_STRING)); assert_eq!(x.description(), SOME_STRING); assert!(x.cause().is_none()); } }