Struct core::fmt::DebugTuple

1.2.0 · source ·
pub struct DebugTuple<'a, 'b: 'a> { /* private fields */ }
Expand description

A struct to help with fmt::Debug implementations.

This is useful when you wish to output a formatted tuple as a part of your Debug::fmt implementation.

This can be constructed by the Formatter::debug_tuple method.

§Examples

use std::fmt;

struct Foo(i32, String);

impl fmt::Debug for Foo {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_tuple("Foo")
           .field(&self.0)
           .field(&self.1)
           .finish()
    }
}

assert_eq!(
    format!("{:?}", Foo(10, "Hello World".to_string())),
    r#"Foo(10, "Hello World")"#,
);

Implementations§

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impl<'a, 'b: 'a> DebugTuple<'a, 'b>

1.2.0 · source

pub fn field(&mut self, value: &dyn Debug) -> &mut Self

Adds a new field to the generated tuple struct output.

§Examples
use std::fmt;

struct Foo(i32, String);

impl fmt::Debug for Foo {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_tuple("Foo")
           .field(&self.0) // We add the first field.
           .field(&self.1) // We add the second field.
           .finish() // We're good to go!
    }
}

assert_eq!(
    format!("{:?}", Foo(10, "Hello World".to_string())),
    r#"Foo(10, "Hello World")"#,
);
source

pub fn field_with<F>(&mut self, value_fmt: F) -> &mut Self
where F: FnOnce(&mut Formatter<'_>) -> Result,

🔬This is a nightly-only experimental API. (debug_closure_helpers #117729)

Adds a new field to the generated tuple struct output.

This method is equivalent to DebugTuple::field, but formats the value using a provided closure rather than by calling Debug::fmt.

source

pub fn finish_non_exhaustive(&mut self) -> Result

🔬This is a nightly-only experimental API. (debug_more_non_exhaustive #127942)

Marks the tuple struct as non-exhaustive, indicating to the reader that there are some other fields that are not shown in the debug representation.

§Examples
#![feature(debug_more_non_exhaustive)]

use std::fmt;

struct Foo(i32, String);

impl fmt::Debug for Foo {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_tuple("Foo")
           .field(&self.0)
           .finish_non_exhaustive() // Show that some other field(s) exist.
    }
}

assert_eq!(
    format!("{:?}", Foo(10, "secret!".to_owned())),
    "Foo(10, ..)",
);
1.2.0 · source

pub fn finish(&mut self) -> Result

Finishes output and returns any error encountered.

§Examples
use std::fmt;

struct Foo(i32, String);

impl fmt::Debug for Foo {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_tuple("Foo")
           .field(&self.0)
           .field(&self.1)
           .finish() // You need to call it to "finish" the
                     // tuple formatting.
    }
}

assert_eq!(
    format!("{:?}", Foo(10, "Hello World".to_string())),
    r#"Foo(10, "Hello World")"#,
);

Auto Trait Implementations§

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impl<'a, 'b> Freeze for DebugTuple<'a, 'b>

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impl<'a, 'b> !RefUnwindSafe for DebugTuple<'a, 'b>

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impl<'a, 'b> !Send for DebugTuple<'a, 'b>

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impl<'a, 'b> !Sync for DebugTuple<'a, 'b>

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impl<'a, 'b> Unpin for DebugTuple<'a, 'b>

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impl<'a, 'b> !UnwindSafe for DebugTuple<'a, 'b>

Blanket Implementations§

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

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.