Struct InputChain 

pub struct InputChain<T> { /* private fields */ }

Chain multiple input sources with fallback behavior.

Sources are tried in the order they were added. The first source that returns Some(value) wins. If all sources return None, the chain uses the default value or returns InputError::NoInput.

Example

use standout_input::{InputChain, ArgSource, StdinSource, DefaultSource};

// Try argument first, then stdin, then use default
let chain = InputChain::<String>::new()
    .try_source(ArgSource::new("message"))
    .try_source(StdinSource::new())
    .try_source(DefaultSource::new("default message".to_string()));

let value = chain.resolve(&matches)?;

Validation

Add validators to check the resolved value:

let chain = InputChain::<String>::new()
    .try_source(ArgSource::new("email"))
    .validate(|s| s.contains('@'), "Must be a valid email");

Interactive sources (prompts, editor) can retry on validation failure.

Implementations

impl<T: Clone + Send + Sync + 'static> InputChain<T>

pub fn new() -> Self

Create a new empty input chain.

pub fn try_source<C: InputCollector<T> + 'static>(self, source: C) -> Self

Add a source to the chain.

Sources are tried in the order they are added.

pub fn try_source_with_kind<C: InputCollector<T> + 'static>( self, source: C, kind: InputSourceKind, ) -> Self

Add a source with an explicit kind.

Use this when the source name doesn’t map to a standard kind.

pub fn validate<F>(self, f: F, error_msg: impl Into<String>) -> Self

where F: Fn(&T) -> bool + Send + Sync + 'static,

Add a validation rule.

The validator is called after a source successfully provides input. If validation fails:

• Interactive sources (where can_retry() is true) will re-prompt
• Non-interactive sources will return a validation error

Multiple validators are checked in order; all must pass.

pub fn validate_with<F>(self, f: F) -> Self

where F: Fn(&T) -> Result<(), String> + Send + Sync + 'static,

Add a validation rule that returns a Result.

Unlike validate, this allows custom error messages per validation failure.

pub fn default(self, value: T) -> Self

Set a default value to use when no source provides input.

This is equivalent to adding a DefaultSource at the end of the chain.

pub fn resolve(&self, matches: &ArgMatches) -> Result<T, InputError>

Resolve the chain and return the input value.

Tries each source in order until one provides input, then runs validation. Returns the value or an error.

pub fn resolve_with_source( &self, matches: &ArgMatches, ) -> Result<ResolvedInput<T>, InputError>

Resolve the chain and return the input with source metadata.

Like resolve, but also returns which source provided the value.

pub fn has_available_source(&self, matches: &ArgMatches) -> bool

Check if any source is available to provide input.

pub fn source_count(&self) -> usize

Get the number of sources in the chain.

Trait Implementations

impl<T> Debug for InputChain<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Clone + Send + Sync + 'static> Default for InputChain<T>

fn default() -> Self

Returns the “default value” for a type.