Struct Immutable 

pub struct Immutable<T>(/* private fields */);

A wrapper that provides read-only access to a value

This type is meant to prevent accidental modifications of values after construction. It can not however, prevent replacement of the value itself. For example:

use cut::Immutable;

let mut val = Immutable::new(10);

// later...
val = Immutable::new(11);

assert_eq!(*val, 11);

use cut::Immutable;

struct Foo {
  bar: Immutable<bool>,
}

impl Foo {
  pub fn new(bar: bool) -> Self {
    Self {
      bar: Immutable::new(bar),
    }
  }

  pub fn bar(&mut self) -> bool {
    // ERROR
    //self.bar = !*self.bar;

    // if From<T> was implemented for Immutable<T>, you might accidently do this:
    //self.bar = (!*self.bar).into();

    // uh oh...
    // atleast you can explictly see that a new Immutable<T> is being assigned
    self.bar = Immutable::new(!*self.bar);

    *self.bar
  }
}

let mut foo = Foo::new(false);

assert_eq!(foo.bar(), true);
assert_eq!(foo.bar(), false);
assert_eq!(foo.bar(), true);

Types with interior mutability such as Cell can still be modified when wrapped. This includes nesting such as the following:

use core::cell::Cell;

use cut::Immutable;

struct Foo {
  bar: Bar,
}

struct Bar {
  baz: Cell<bool>,
}

let foo = Immutable::new(Foo {
  bar: Bar {
    baz: Cell::new(false),
  },
});

foo.bar.baz.set(true);

assert_eq!(foo.bar.baz.get(), true);

Implementations

impl<T> Immutable<T>

pub const fn new(v: T) -> Self

Wrap a value v to ensure read-only access going forward

pub fn get(&self) -> &T

Get a reference to the wrapped read-only value

Trait Implementations

impl<T: Clone> Clone for Immutable<T>

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Copy> Copy for Immutable<T>

impl<T: Debug> Debug for Immutable<T>

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

Formats the value using the given formatter.

impl<T: Default> Default for Immutable<T>

fn default() -> Self

Returns the “default value” for a type.

impl<T> Deref for Immutable<T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<T: Eq> Eq for Immutable<T>

impl<T: Hash> Hash for Immutable<T>

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: Ord> Ord for Immutable<T>

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

fn clamp_to<R>(self, range: R) -> Self

where Self: Sized, R: ClampBounds<Self>,

🔬This is a nightly-only experimental API. (clamp_to)

Restrict a value to a certain range.

impl<T: PartialEq> PartialEq for Immutable<T>

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl<T: PartialOrd> PartialOrd for Immutable<T>

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T: PartialEq> StructuralPartialEq for Immutable<T>