Trait Any 

pub trait Any: 'static {
    // Required method
    fn type_id(&self) -> TypeId;
}

A trait to emulate dynamic typing.

Most types implement Any. However, any type which contains a non-'static reference does not. See the module-level documentation for more details.

Required Methods

fn type_id(&self) -> TypeId

This item is validated for IEC 61508 (SIL 2) and ISO 26262 (ASIL B).

Gets the TypeId of self.

If called on a dyn Any trait object (or a trait object of a subtrait of Any), this returns the TypeId of the underlying concrete type, not that of dyn Any itself.

Examples

use std::any::{Any, TypeId};

fn is_string(s: &dyn Any) -> bool {
    TypeId::of::<String>() == s.type_id()
}

assert_eq!(is_string(&0), false);
assert_eq!(is_string(&"cookie monster".to_string()), true);

Implementations

impl dyn Any

pub fn is<T: Any>(&self) -> bool

Returns true if the inner type is the same as T.

Examples

use std::any::Any;

fn is_string(s: &dyn Any) {
    if s.is::<String>() {
        println!("It's a string!");
    } else {
        println!("Not a string...");
    }
}

is_string(&0);
is_string(&"cookie monster".to_string());

pub fn downcast_ref<T: Any>(&self) -> Option<&T>

Returns some reference to the inner value if it is of type T, or None if it isn’t.

Examples

use std::any::Any;

fn print_if_string(s: &dyn Any) {
    if let Some(string) = s.downcast_ref::<String>() {
        println!("It's a string({}): '{}'", string.len(), string);
    } else {
        println!("Not a string...");
    }
}

print_if_string(&0);
print_if_string(&"cookie monster".to_string());

pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T>

Returns some mutable reference to the inner value if it is of type T, or None if it isn’t.

Examples

use std::any::Any;

fn modify_if_u32(s: &mut dyn Any) {
    if let Some(num) = s.downcast_mut::<u32>() {
        *num = 42;
    }
}

let mut x = 10u32;
let mut s = "starlord".to_string();

modify_if_u32(&mut x);
modify_if_u32(&mut s);

assert_eq!(x, 42);
assert_eq!(&s, "starlord");

pub unsafe fn downcast_unchecked_ref<T: Any>(&self) -> &T

🔬This is a nightly-only experimental API. (downcast_unchecked #90850)

Returns a reference to the inner value as type dyn T.

Examples

#![feature(downcast_unchecked)]

use std::any::Any;

let x: Box<dyn Any> = Box::new(1_usize);

unsafe {
    assert_eq!(*x.downcast_unchecked_ref::<usize>(), 1);
}

Safety

The contained value must be of type T. Calling this method with the incorrect type is undefined behavior.

pub unsafe fn downcast_unchecked_mut<T: Any>(&mut self) -> &mut T

🔬This is a nightly-only experimental API. (downcast_unchecked #90850)

Returns a mutable reference to the inner value as type dyn T.

Examples

#![feature(downcast_unchecked)]

use std::any::Any;

let mut x: Box<dyn Any> = Box::new(1_usize);

unsafe {
    *x.downcast_unchecked_mut::<usize>() += 1;
}

assert_eq!(*x.downcast_ref::<usize>().unwrap(), 2);

Safety

The contained value must be of type T. Calling this method with the incorrect type is undefined behavior.

impl dyn Any + Send

pub fn is<T: Any>(&self) -> bool

Forwards to the method defined on the type dyn Any.

Examples

use std::any::Any;

fn is_string(s: &(dyn Any + Send)) {
    if s.is::<String>() {
        println!("It's a string!");
    } else {
        println!("Not a string...");
    }
}

is_string(&0);
is_string(&"cookie monster".to_string());

pub fn downcast_ref<T: Any>(&self) -> Option<&T>

Forwards to the method defined on the type dyn Any.

Examples

use std::any::Any;

fn print_if_string(s: &(dyn Any + Send)) {
    if let Some(string) = s.downcast_ref::<String>() {
        println!("It's a string({}): '{}'", string.len(), string);
    } else {
        println!("Not a string...");
    }
}

print_if_string(&0);
print_if_string(&"cookie monster".to_string());

pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T>

Forwards to the method defined on the type dyn Any.

Examples

use std::any::Any;

fn modify_if_u32(s: &mut (dyn Any + Send)) {
    if let Some(num) = s.downcast_mut::<u32>() {
        *num = 42;
    }
}

let mut x = 10u32;
let mut s = "starlord".to_string();

modify_if_u32(&mut x);
modify_if_u32(&mut s);

assert_eq!(x, 42);
assert_eq!(&s, "starlord");

pub unsafe fn downcast_unchecked_ref<T: Any>(&self) -> &T

🔬This is a nightly-only experimental API. (downcast_unchecked #90850)

Forwards to the method defined on the type dyn Any.

Examples

#![feature(downcast_unchecked)]

use std::any::Any;

let x: Box<dyn Any> = Box::new(1_usize);

unsafe {
    assert_eq!(*x.downcast_unchecked_ref::<usize>(), 1);
}

Safety

The contained value must be of type T. Calling this method with the incorrect type is undefined behavior.

pub unsafe fn downcast_unchecked_mut<T: Any>(&mut self) -> &mut T

🔬This is a nightly-only experimental API. (downcast_unchecked #90850)

Forwards to the method defined on the type dyn Any.

Examples

#![feature(downcast_unchecked)]

use std::any::Any;

let mut x: Box<dyn Any> = Box::new(1_usize);

unsafe {
    *x.downcast_unchecked_mut::<usize>() += 1;
}

assert_eq!(*x.downcast_ref::<usize>().unwrap(), 2);

Safety

The contained value must be of type T. Calling this method with the incorrect type is undefined behavior.

impl dyn Any + Send + Sync

pub fn is<T: Any>(&self) -> bool

Forwards to the method defined on the type Any.

Examples

use std::any::Any;

fn is_string(s: &(dyn Any + Send + Sync)) {
    if s.is::<String>() {
        println!("It's a string!");
    } else {
        println!("Not a string...");
    }
}

is_string(&0);
is_string(&"cookie monster".to_string());

pub fn downcast_ref<T: Any>(&self) -> Option<&T>

Forwards to the method defined on the type Any.

Examples

use std::any::Any;

fn print_if_string(s: &(dyn Any + Send + Sync)) {
    if let Some(string) = s.downcast_ref::<String>() {
        println!("It's a string({}): '{}'", string.len(), string);
    } else {
        println!("Not a string...");
    }
}

print_if_string(&0);
print_if_string(&"cookie monster".to_string());

pub fn downcast_mut<T: Any>(&mut self) -> Option<&mut T>

Forwards to the method defined on the type Any.

Examples

use std::any::Any;

fn modify_if_u32(s: &mut (dyn Any + Send + Sync)) {
    if let Some(num) = s.downcast_mut::<u32>() {
        *num = 42;
    }
}

let mut x = 10u32;
let mut s = "starlord".to_string();

modify_if_u32(&mut x);
modify_if_u32(&mut s);

assert_eq!(x, 42);
assert_eq!(&s, "starlord");

pub unsafe fn downcast_unchecked_ref<T: Any>(&self) -> &T

🔬This is a nightly-only experimental API. (downcast_unchecked #90850)

Forwards to the method defined on the type Any.

Examples

#![feature(downcast_unchecked)]

use std::any::Any;

let x: Box<dyn Any> = Box::new(1_usize);

unsafe {
    assert_eq!(*x.downcast_unchecked_ref::<usize>(), 1);
}

Safety

The contained value must be of type T. Calling this method with the incorrect type is undefined behavior.

pub unsafe fn downcast_unchecked_mut<T: Any>(&mut self) -> &mut T

🔬This is a nightly-only experimental API. (downcast_unchecked #90850)

Forwards to the method defined on the type Any.

Examples

#![feature(downcast_unchecked)]

use std::any::Any;

let mut x: Box<dyn Any> = Box::new(1_usize);

unsafe {
    *x.downcast_unchecked_mut::<usize>() += 1;
}

assert_eq!(*x.downcast_ref::<usize>().unwrap(), 2);

Safety

The contained value must be of type T. Calling this method with the incorrect type is undefined behavior.

Trait Implementations

impl Debug for dyn Any

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

This item is validated for IEC 61508 (SIL 2) and ISO 26262 (ASIL B).

Formats the value using the given formatter.

impl Debug for dyn Any + Send

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

This item is validated for IEC 61508 (SIL 2) and ISO 26262 (ASIL B).

Formats the value using the given formatter.

impl Debug for dyn Any + Send + Sync

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

This item is validated for IEC 61508 (SIL 2) and ISO 26262 (ASIL B).

Formats the value using the given formatter.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl<T: 'static + ?Sized> Any for T