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//! Getting data from a human, from stdin. //! //! This library provides methods for getting information from a human. They all work on buffered //! lines of input (this is how terminals work unless you put them in a different mode). They are //! useful for building simple interactive command line apps (for example how *pacman* gets //! confirmantion during a system upgrade on arch linux). They are also useful for learning, when //! you want to be able to get data easily. use std::{ io::{self, Write}, str::FromStr, }; /// Get a line of text from the user. /// /// The question is displayed first. This method converts empty text into `None`. Any whitespace /// around the input, including the line ending, will be trimmed. /// /// # Examples /// /// ```rust,no_run /// # use std::io; /// let name = read_human::read_string("Please enter your name: ")?; /// if let Some(name) = name { /// // An empty string would have been converted into `None` /// assert!(name != ""); /// } /// # Ok::<(), io::Error>(()) /// ``` pub fn read_string(question: &str) -> io::Result<Option<String>> { print!("{}: ", question); io::stdout().flush()?; let mut buf = String::new(); io::stdin().read_line(&mut buf)?; Ok(if buf.trim() == "" { None } else { Some(buf.trim().to_owned()) }) } /// Get a line of non-empty text from the user. /// /// The question is displayed first. This method converts empty text into `None`. Any whitespace /// around the input, including the line ending, will be trimmed. /// /// This function will keep asking for input until it gets a non-empty string. /// /// # Examples /// /// ```rust,no_run /// # use std::io; /// let name = read_human::read_string_nonempty("Please enter your name: ")?; /// // The function will not return until we have a non-empty string /// assert!(name != ""); /// # Ok::<(), io::Error>(()) /// ``` pub fn read_string_nonempty(question: &str) -> io::Result<String> { loop { match read_string(question)? { Some(s) => return Ok(s), None => println!("Input must not be empty."), }; } } /// Get a line of from the user without displaying a question first. /// /// This method converts empty text into `None`. Any whitespace /// around the input, including the line ending, will be trimmed. /// /// # Examples /// /// ```rust,no_run /// # use std::io; /// let name = read_human::read_string_noquestion()?; /// if let Some(name) = name { /// // An empty string would have been converted into `None` /// assert!(name != ""); /// } /// # Ok::<(), io::Error>(()) /// ``` pub fn read_string_noquestion() -> io::Result<Option<String>> { io::stdout().flush()?; let mut buf = String::new(); io::stdin().read_line(&mut buf)?; Ok(if buf.trim() == "" { None } else { Some(buf.trim().to_owned()) }) } /// Allow the user to choose between a set of choices, and optionally give them a default choice. /// /// The default will be selected if the user just hits enter. If the user writes something that's /// not one of the choices, the function will ask for another line of input. /// /// # Panics /// /// This function will panic if the default value is >= the number of options. /// /// # Examples /// /// ```rust,no_run /// # use std::io; /// let choice = read_human::read_choice("What is your gender?", &["male", "female"], None)?; /// // Must be 0 (male) or 1 (female) /// assert!(choice <= 2); /// # Ok::<(), io::Error>(()) /// ``` pub fn read_choice( question: &str, options: &[impl AsRef<str>], default: Option<usize>, ) -> io::Result<usize> { assert!( if let Some(val) = default { val < options.len() } else { true }, "default index must be in the options slice" ); loop { print!("{} [", question); let mut options_iter = options.iter().enumerate(); if let Some((_, opt)) = options_iter.next() { print!(r#"1: "{}""#, opt.as_ref()); } for (idx, option) in options_iter { print!(r#", {}: "{}""#, idx + 1, option.as_ref()); } if let Some(d) = default { print!(" (default: {})", d + 1); } print!("]: "); io::stdout().flush()?; let mut buf = String::new(); io::stdin().read_line(&mut buf)?; let ans = buf.trim(); if let Some(val) = default { if ans == "" { return Ok(val); } } match ans.parse::<usize>() { Ok(a) => { let ans = a - 1; if ans < options.len() { return Ok(ans); } else { println!("{} is not a valid option (too big)", ans); } } Err(_) => { println!("{} is not a valid option", ans); } } } } /// Read in any type that implementd `FromStr` from stdio. /// /// If the text was empty, or couldn't be converted, then the user will be asked for more input. /// /// # Examples /// /// ```rust,no_run /// # use std::io; /// let number: u32 = read_human::read_custom_nonempty("How old are you")?; /// # Ok::<(), io::Error>(()) /// ``` pub fn read_custom_nonempty<T: FromStr>(question: &str) -> io::Result<T> { loop { let raw = read_string_nonempty(question)?; match raw.parse::<T>() { Ok(t) => return Ok(t), Err(_) => println!("{} is not valid", raw), } } } /// Read in any type that implementd `FromStr` from stdio. /// /// If the text couldn't be converted, then the user will be asked for more input. /// /// # Examples /// /// ```rust,no_run /// # use std::io; /// let number: Option<u32> = read_human::read_custom( /// "Let us know how many times you've visited, if applicable")?; /// # Ok::<(), io::Error>(()) /// ``` pub fn read_custom<T: FromStr>(question: &str) -> io::Result<Option<T>> { loop { let raw = match read_string(question)? { Some(s) => s, None => return Ok(None), }; match raw.parse::<T>() { Ok(t) => return Ok(Some(t)), Err(_) => println!("{} is not valid", raw), } } } /// Read in any type that implementd `FromStr` from stdio. /// /// If the text couldn't be converted, then the user will be asked for more input. /// /// # Examples /// /// ```rust,no_run /// # use std::io; /// let number: Option<u32> = read_human::read_custom_noquestion()?; /// # Ok::<(), io::Error>(()) /// ``` pub fn read_custom_noquestion<T: FromStr>() -> io::Result<Option<T>> { loop { let raw = match read_string_noquestion()? { Some(s) => s, None => return Ok(None), }; match raw.parse::<T>() { Ok(t) => return Ok(Some(t)), Err(_) => println!("{} is not valid", raw), } } }