Struct Capture

pub struct Capture<Data>(pub Data);

A utility wrapper which simply wraps around data to be captured and allows methods to define desired closures.

Closures defined in this crate are built by

• Capture(data) which does nothing but captures the data,
• followed by:
  • fun(fn) to create a Closure
  • fun_ref(fn) to create a ClosureRef
  • fun_option_ref(fn) to create a ClosureOptRef
  • fun_result_ref(fn) to create a ClosureResRef

where fn is a non-capturing anonymous function of the correct signature.

All these methods are consuming moving the data into the corresponding closure.

The desired way to capture the data is decided by the caller:

• Capture(data) moves the data into the capture, and eventually to the closure,
• Capture(&data) only captures a reference to the data,
• Capture(data.clone()) moves a clone of the data, etc.

Important note related to how we capture and closure variants:

• Closure created by the fun is sufficient for all types:

  • when we capture by reference, and/or
  • when we return a value, rather than a reference.

• To deal with lifetime errors, we need:

  • ClosureRef created by fun_ref when we capture the ownership of the data and return a reference,
  • ClosureOptRef created by fun_option_ref when we capture the ownership of the data and return an Option of a reference,
  • ClosureResRef created by fun_result_ref when we capture the ownership of the data and return a Result of a reference.

Examples

use orx_closure::*;
use std::rc::Rc;

let numbers = vec![42];

// fun is sufficient in all cases when the data is captured by reference
let fun = Capture(&numbers).fun(|vec, i| vec[i]);
assert_eq!(42, fun.call(0));

let fun = Capture(&numbers).fun(|vec, i| &vec[i]);
assert_eq!(&42, fun.call(0));

let fun = Capture(&numbers).fun(|vec, i| vec.get(i));
assert_eq!(Some(&42), fun.call(0));

let fun = Capture(&numbers).fun(|vec, i| vec.get(i).ok_or("no-data"));
assert_eq!(Ok(&42), fun.call(0));

// we need the other variants
let fun = Capture(numbers.clone()).fun_ref(|vec, i| &vec[i]);
assert_eq!(&42, fun.call(0));

let fun = Capture(Rc::new(numbers.clone())).fun_option_ref(|vec, i| vec.get(i));
assert_eq!(Some(&42), fun.call(0));

let fun = Capture(numbers).fun_result_ref(|vec, i| vec.get(i).ok_or("no-data"));
assert_eq!(Ok(&42), fun.call(0));

Tuple Fields

0: Data

Implementations

impl<Data> Capture<Data>

pub fn fun<In, Out>(self, fun: fn(&Data, In) -> Out) -> Closure<Data, In, Out>

Defines a Closure<Data, In, Out> capturing Data and defining In -> Out transformation.

Consumes the Capture and moves the captured data inside the created closure.

Example

use orx_closure::Capture;

let base = 2;
let modulo = Capture(base).fun(|b, n| n % b);

assert_eq!(0, modulo.call(42));
assert_eq!(1, modulo.call(7));

pub fn fun_ref<In, Out: ?Sized>( self, fun: fn(&Data, In) -> &Out, ) -> ClosureRef<Data, In, Out>

Defines a ClosureRef<Data, In, Out> capturing Data and defining In -> &Out transformation.

Consumes the Capture and moves the captured data inside the created closure.

Note tha twe only need this closure variant when:

• the data is captured by ownership rather than as a reference, and
• we want to return a reference.

Example

use orx_closure::Capture;

struct Person { name: String }
let people = [Person { name: "john".to_string() }, Person { name: "doe".to_string() }];
// name_of_person_with_id: ClosureRef<[Person; 2], usize, str>
let name_of_person_with_id =
    Capture(people).fun_ref(|ppl, id: usize| ppl[id].name.as_str());

assert_eq!("john", name_of_person_with_id.call(0));

pub fn fun_option_ref<In, Out: ?Sized>( self, fun: fn(&Data, In) -> Option<&Out>, ) -> ClosureOptRef<Data, In, Out>

Defines a ClosureOptRef<Data, In, Out> capturing Data and defining In -> Option<&Out> transformation.

Consumes the Capture and moves the captured data inside the created closure.

Note tha twe only need this closure variant when:

• the data is captured by ownership rather than as a reference, and
• we want to return an Option of a reference.

Example

use orx_closure::Capture;

struct Person { name: String }
let people = [Person { name: "john".to_string() }, Person { name: "doe".to_string() }];
// name_of_person_with_id: ClosureOptRef<[Person; 2], usize, str>
let name_of_person_with_id =
    Capture(people).fun_option_ref(|ppl, id: usize| ppl.get(id).map(|p| p.name.as_str()));

assert_eq!(Some("john"), name_of_person_with_id.call(0));
assert_eq!(None, name_of_person_with_id.call(42));

// alternatively
let fun = name_of_person_with_id.as_fn();
assert_eq!(Some("doe"), fun(1));

pub fn fun_result_ref<In, Out: ?Sized, Error>( self, fun: fn(&Data, In) -> Result<&Out, Error>, ) -> ClosureResRef<Data, In, Out, Error>

Defines a ClosureResRef<Data, In, Out, Error> capturing Data and defining In -> Result<&Out, Error> transformation.

Consumes the Capture and moves the captured data inside the created closure.

Note tha twe only need this closure variant when:

• the data is captured by ownership rather than as a reference, and
• we want to return a Result of a reference.

Example

use orx_closure::Capture;

struct Person { name: String }
let people = [Person { name: "john".to_string() }, Person { name: "doe".to_string() }];
// name_of_person_with_id: ClosureResRef<[Person; 2], usize, str, String>
let name_of_person_with_id = Capture(people).fun_result_ref(|ppl, id: usize| {
    ppl.get(id)
        .map(|p| p.name.as_str())
        .ok_or_else(|| "unknown id".to_string())
});

assert_eq!(Ok("john"), name_of_person_with_id.call(0));
assert_eq!(Err("unknown id".to_string()), name_of_person_with_id.call(42));

pub fn into_captured_data(self) -> Data

Consumes the Capture and returns back the captured data.

Example

use orx_closure::*;

let data = vec![42];
let capture = Capture(data);

let data_back = capture.into_captured_data();
assert_eq!(vec![42], data_back);