Struct DeferredRead

pub struct DeferredRead<T>(pub PathBuf, _)
where
    T: ReadFrom;

A wrapper that defers the reading of a file until it is actually needed.

The only thing you can do with a DeferredRead is to call DeferredRead::perform_read, which will read the file and return the value.

See the DeferredRead::perform_read method for more details.

Tuple Fields

0: PathBuf

Implementations

impl<T> DeferredRead<T>

where T: ReadFrom,

pub fn perform_read(&self) -> Result<T>

Performs the read and returns the value.

If the value changed on disk since the DeferredRead was created, then the new value will be read from disk and returned.

For a cached version see DeferredReadOrOwn.

Examples

use std::path::Path;
use dir_structure::DirStructureItem;
use dir_structure::DeferredRead;

#[derive(dir_structure::DirStructure)]
struct Dir {
    #[dir_structure(path = "f.txt")]
    f: DeferredRead<String>,
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let d = Path::new("dir");

    std::fs::create_dir_all(&d)?;
    std::fs::write(d.join("f.txt"), "Hello, world!")?;

    let dir = Dir::read(&d)?;
    assert_eq!(dir.f.perform_read()?, "Hello, world!");

    std::fs::write(d.join("f.txt"), "Goodbye, world!")?;
    assert_eq!(dir.f.perform_read()?, "Goodbye, world!");

    Ok(())
}

Trait Implementations

impl<T> Clone for DeferredRead<T>

where T: ReadFrom + Clone,

fn clone(&self) -> DeferredRead<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T> Debug for DeferredRead<T>

where T: ReadFrom + Debug,

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

Formats the value using the given formatter.

impl<T> Hash for DeferredRead<T>

where T: ReadFrom + Hash,

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T> ReadFrom for DeferredRead<T>

where T: ReadFrom,

fn read_from(path: &Path) -> Result<Self>

where Self: Sized,

Reads the structure from the specified path, which can be either a file or a directory.

impl<T> WriteTo for DeferredRead<T>

where T: ReadFrom + WriteTo,

fn write_to(&self, path: &Path) -> Result<()>

Writes the structure to the specified path.