DebugTuple in alloc::fmt - Rust
Description: A struct to help with `fmt::Debug` implementations.

## DebugTuple

# Struct DebugTuple

1.36.0 · Source

    pub struct DebugTuple<'a, 'b>where
        '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> DebugTuple<'a, 'b>
where 'b: 'a,

1.2.0 · Source

#### pub fn field(&mut self, value: &dyn Debug) -> &mut DebugTuple<'a, 'b>

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")"#,
    );

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#### pub fn field_with<F>(&mut self, value_fmt: F) -> &mut DebugTuple<'a, 'b>
where F: FnOnce(&mut Formatter<'_>) -> Result<(), Error>,

🔬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`.

1.83.0 · Source

#### pub fn finish_non_exhaustive(&mut self) -> Result<(), Error>

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

    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<(), Error>

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.