Crate ensure

Object implementing Ensure trait are in unknown inital state and can be brought to a target state.

By calling met() we can be ensured that object is in its target state regardles if it was already in that state or had to be brought to it. If object was already in target state nothing happens. Otherwise met() will call meet() on provided MeetAction type to bring the object into its target state.

If object implements Clone method met_verify() can be used to make sure that object fulfills Met condition after MeetAction type has been preformed.

Closures returning TryMetResult that also return closure in TryMetResult::MeetAction variant automatically implement Ensure trait. Helper function ensure can be used to call met() on such closure.

Example

This program will create file only if it does not exist.

use std::path::Path;
use std::fs::File;
use ensure::ensure;
use ensure::TryMetResult::*;

let path = Path::new("/tmp/foo.txt");

ensure(|| {
    if path.exists() {
        Met(())
    } else {
        MeetAction(|| {
            File::create(&path).unwrap();
        })
    }
});

Structs

Existing	Mark T as something that exists
NonExisting	Mark T as something that does not exists
UnmetError

Enums

MetResult	Result of ensuring target state with met()
TryMetResult	Result of verification if object is in target state with try_met()

Traits

Ensure	Implement for types of objects that can be brought to target state
Existential	Extends any T with method allowing to declare it as existing or non-existing
MeetAction	Function that can be used to bring object in its target state

Functions

ensure

Run met() on object implementing Ensure and return its value. This is useful with closures implementing Ensure.