Read Input

A simple tool that asks for data until the data is valid.

Help

If you run into any issues or need help with using read_input in your project please email incoming+efunb/read_input@incoming.gitlab.com

Why you need it

When writing programs you will often need to take input from the user. If the user inputs invalid information the program needs to ask them again. Having to make this loop distracts from the useful logic in your program.

read_input attempts to make it easy to get input from the user without having to think about converting types.

How to use

Add

read_input = "0.3"

to your cargo.toml under [dependencies] and add

extern crate read_input;

use read_input::*;

to your main file.

You can get input with.

let input = input_new::<Type>().get();

Where Type is the type you want. Currently the you can use all types that implement std::str::FromStr. This currently includes the standard library types isize, usize, i8, u8, i16, u16, f32, i32, u32, f64, i64, u64, i128, u128, char, Ipv4Addr, Ipv6Addr, SocketAddrV4, SocketAddrV6 and String. Many crates also implement std::str::FromStr for their types.

For example, if you want a valid unsigned 32bit value you could write.

let input = input_new::<u32>().get();

Often rust can work out the type so you can skip explicitly stating the type.

let input = input_new().get();

Input message

Custom messages are written on the same line as input and are specified with .msg(). For example.

let username: String = input_new().msg("Please input your name: ").get();

Default values

If the user presses enter before typing anything the program will return a default value when .default() is used.

let input = input_new().msg("Please input pi: ").default(3.141).get();

Change error message

The default error message is "That value does not pass please try again". You can change the error message with .err(). For example.

let input = input_new::<u32>()
    .msg("Please input a positive number: ")
    .err("That does not look like a positive number. Please try again")
    .get();

Add Checks

You can add your own checks to ensure the value meets your criteria. If you want a integer between 4 and 9 you could write.

let input = input_new().add_test(|x| 4 < *x && *x < 9).get();

In the same style you can specify custom test errors and multiple tests. If you want a value between 4 and 9 that is not 6 you could write.

let input = input_new()
    .msg("Please input a number between 4 and 9 that is not 6: ")
    .add_test(|x| 4 < *x && *x < 9)
    .add_err_test(
        |x| *x != 6,
        "That value is 6! I dont want 6. Please try again"
    )
    .err("That does not look like a number between 4 and 9. Please try again")
    .get();

Match errors

You can specify custom error messages that depend on the errors produced by from_str() with .err_match(). An example of how this can be done can be seen here.

Shortcut functions

Using input_new().get() can be a little verbose in simple situations. The functions simple_input() and valid_input() can make things simpler.

simple_input() is the same as input_new().get().

valid_input(|x| 4 < *x && *x < 9) is the same as input_new().add_test(|x| 4 < *x && *x < 9).get().

How to use with custom type

To use read_input with a custom type you need to implement std::str::FromStr for that type.

FromStr documentation

Working example

More complex examples

simple_guessing_game. The guessing game form the rust book made to use read_input.
guessing_game. The guessing game form the rust book made to use read_input + some extra features.
how_long_until. Program that uses read_input with the crate chrono.
point_input. Program written to show the use of the err_match() method.

Docs

API Documentation

Warning

If you are viewing this from GitHub then this is a read only copy. Please contribute to the GitLab copy here.

read_input 0.4.0