Struct ValueField

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pub struct ValueField<'a> { /* private fields */ }

Expand description

Defines behavior for a value-menu field.

It manages

its message
its formatting
the return value type
the default value

§Examples

For a make-license CLI program for example, you can use

use ezmenulib::ValueField;
let author: String = ValueField::from("Give the author of the license")
    .build_init()
    .unwrap();

Implementations§

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impl<'a> ValueField<'a>

Constructor methods defining how the field behaves

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pub fn fmt(self, fmt: ValueFieldFormatting<'a>) -> ValueField<'a>

Give a custom formatting for the field.

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pub fn default_value(self, default: &'a str) -> ValueField<'a>

Give the default value accepted by the field.

If the value type is incorrect, the ValueField::build or ValueField::build_init method will return an Err value emphasizing that the default value type is incorrect.

So when instantiating the field with a provided default value, it will not panic and it will print the default value even if it is incorrect (if the format rule default is set to true).

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pub fn default_env(self, var: &'a str) -> Result<ValueField<'a>, MenuError>

Give the default value of the field, passing by an environment variable.

If the provided environment variable is incorrect, it will return an error (See MenuError::EnvVar variant).

If the value type of the variable is incorrect, the ValueField::build or ValueField::build_init method will return an Err value emphasizing that the default value type is incorrect.

So when instantiating the field with a provided default value, it will not panic and it will print the default value even if it is incorrect (if the format rule default is set to true).

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pub fn build_init<T>(&self) -> Result<T, MenuError>
where T: FromStr, <T as FromStr>::Err: 'static + Debug,

Builds the field without specifying standard input and output files.

It initializes instance of Stdin and Stdout.

§Example

use ezmenulib::prelude::*;
let age: MenuResult<u8> = ValueField::from("How old are you")
    .build_init();

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pub fn build<T>( &self, reader: &mut BufReader<Stdin>, writer: &mut Stdout, ) -> Result<T, MenuError>
where T: FromStr, <T as FromStr>::Err: 'static + Debug,

Builds the field. It prints the message according to its formatting, then returns the corresponding value.

You need to provide the reader for the input, and the writer for the output. It returns a MenuResult if there was an IO error, or if the default value type is incorrect.

§Example

Supposing you have declared your own Stdin and Stdout in your program, you can do so:

use std::io::{stdin, stdout};

let stdin = stdin();
let mut stdout = stdout();

let author: String = ValueField::from("Author")
    .build(&stdin, &mut stdout)
    .unwrap();

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pub fn build_with<T, R, W>( &self, stream: &mut MenuStream<'_, R, W>, ) -> Result<T, MenuError>
where T: FromStr, <T as FromStr>::Err: 'static + Debug, R: BufRead, W: Write,

Builds the fields with a given menu stream. It prints out the message to the stream according to its formatting, then returns the corresponding value.

You need to instantiate beforehand the MenuStream to use this method.

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