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Trait std::any::Any

1.0.0 · source · 
pub trait Any: 'static {
 fn type_id(&self) -> TypeId;
}
Expand description

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

1.34.0 · source

fn type_id(&self) -> TypeId

Gets the TypeId of self.

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);
Run

Implementations

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impl<A> Box<dyn Any + 'static, A> where
A: Allocator,

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pub fn downcast<T>(self) -> Result<Box<T, A>, Box<dyn Any + 'static, A>> where
T: Any,

Attempt to downcast the box to a concrete type.

Examples 
use std::any::Any;
fn print_if_string(value: Box<dyn Any>) {
 if let Ok(string) = value.downcast::<String>() {
 println!("String ({}): {}", string.len(), string);
 }
}
let my_string = "Hello World".to_string();
print_if_string(Box::new(my_string));
print_if_string(Box::new(0i8));
Run
source

pub unsafe fn downcast_unchecked<T>(self) -> Box<T, A>iNotable traits for Box<I, A>impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W> where
T: Any,

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

Downcasts the box to a concrete type.

For a safe alternative see downcast.

Examples 
#![feature(downcast_unchecked)]
use std::any::Any;
let x: Box<dyn Any> = Box::new(1_usize);
unsafe {
 assert_eq!(*x.downcast_unchecked::<usize>(), 1);
}
Run
Safety

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

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impl<A> Box<dyn Any + Send + 'static, A> where
A: Allocator,

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pub fn downcast<T>(self) -> Result<Box<T, A>, Box<dyn Any + Send + 'static, A>> where
T: Any,

Attempt to downcast the box to a concrete type.

Examples 
use std::any::Any;
fn print_if_string(value: Box<dyn Any + Send>) {
 if let Ok(string) = value.downcast::<String>() {
 println!("String ({}): {}", string.len(), string);
 }
}
let my_string = "Hello World".to_string();
print_if_string(Box::new(my_string));
print_if_string(Box::new(0i8));
Run
source

pub unsafe fn downcast_unchecked<T>(self) -> Box<T, A>iNotable traits for Box<I, A>impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W> where
T: Any,

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

Downcasts the box to a concrete type.

For a safe alternative see downcast.

Examples 
#![feature(downcast_unchecked)]
use std::any::Any;
let x: Box<dyn Any + Send> = Box::new(1_usize);
unsafe {
 assert_eq!(*x.downcast_unchecked::<usize>(), 1);
}
Run
Safety

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

source

impl<A> Box<dyn Any + Sync + Send + 'static, A> where
A: Allocator,

1.51.0 · source

pub fn downcast<T>(
self
) -> Result<Box<T, A>, Box<dyn Any + Sync + Send + 'static, A>> where
T: Any,

Attempt to downcast the box to a concrete type.

Examples 
use std::any::Any;
fn print_if_string(value: Box<dyn Any + Send + Sync>) {
 if let Ok(string) = value.downcast::<String>() {
 println!("String ({}): {}", string.len(), string);
 }
}
let my_string = "Hello World".to_string();
print_if_string(Box::new(my_string));
print_if_string(Box::new(0i8));
Run
source

pub unsafe fn downcast_unchecked<T>(self) -> Box<T, A>iNotable traits for Box<I, A>impl<I, A> Iterator for Box<I, A> where
I: Iterator + ?Sized,
A: Allocator, type Item = <I as Iterator>::Item;impl<F, A> Future for Box<F, A> where
F: Future + Unpin + ?Sized,
A: Allocator + 'static, type Output = <F as Future>::Output;impl<R: Read + ?Sized> Read for Box<R>impl<W: Write + ?Sized> Write for Box<W> where
T: Any,

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

Downcasts the box to a concrete type.

For a safe alternative see downcast.

Examples 
#![feature(downcast_unchecked)]
use std::any::Any;
let x: Box<dyn Any + Send + Sync> = Box::new(1_usize);
unsafe {
 assert_eq!(*x.downcast_unchecked::<usize>(), 1);
}
Run
Safety

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

source

impl dyn Any + 'static

source

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

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());
Run
source

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

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());
Run
source

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

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");
Run
source

pub unsafe fn downcast_ref_unchecked<T>(&self) -> &T where
T: Any,

🔬 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_ref_unchecked::<usize>(), 1);
}
Run
Safety

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

source

pub unsafe fn downcast_mut_unchecked<T>(&mut self) -> &mut T where
T: Any,

🔬 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_mut_unchecked::<usize>() += 1;
}
assert_eq!(*x.downcast_ref::<usize>().unwrap(), 2);
Run
Safety

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

source

impl dyn Any + Send + 'static

source

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

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());
Run
source

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

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());
Run
source

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

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");
Run
source

pub unsafe fn downcast_ref_unchecked<T>(&self) -> &T where
T: Any,

🔬 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_ref_unchecked::<usize>(), 1);
}
Run
Safety

Same as the method on the type dyn Any.

source

pub unsafe fn downcast_mut_unchecked<T>(&mut self) -> &mut T where
T: Any,

🔬 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_mut_unchecked::<usize>() += 1;
}
assert_eq!(*x.downcast_ref::<usize>().unwrap(), 2);
Run
Safety

Same as the method on the type dyn Any.

source

impl dyn Any + Sync + Send + 'static

1.28.0 · source

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

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());
Run
1.28.0 · source

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

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());
Run
1.28.0 · source

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

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");
Run
source

pub unsafe fn downcast_ref_unchecked<T>(&self) -> &T where
T: Any,

🔬 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_ref_unchecked::<usize>(), 1);
}
Run
source

pub unsafe fn downcast_mut_unchecked<T>(&mut self) -> &mut T where
T: Any,

🔬 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_mut_unchecked::<usize>() += 1;
}
assert_eq!(*x.downcast_ref::<usize>().unwrap(), 2);
Run

Trait Implementations

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impl Debug for dyn Any + 'static

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

Formats the value using the given formatter. Read more

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impl Debug for dyn Any + Send + 'static

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

Formats the value using the given formatter. Read more

1.28.0 · source

impl Debug for dyn Any + Sync + Send + 'static

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

Formats the value using the given formatter. Read more

Implementors

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

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