Struct kernel::fmt::DebugStruct

1.2.0 · source ·
pub(crate) struct DebugStruct<'a, 'b>
where 'b: 'a,
{ fmt: &'a mut Formatter<'b>, result: Result<(), Error>, has_fields: bool, }
Expand description

A struct to help with fmt::Debug implementations.

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

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

§Examples

use std::fmt;

struct Foo {
    bar: i32,
    baz: String,
}

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

assert_eq!(
    format!("{:?}", Foo { bar: 10, baz: "Hello World".to_string() }),
    "Foo { bar: 10, baz: \"Hello World\" }",
);

Fields§

§fmt: &'a mut Formatter<'b>§result: Result<(), Error>§has_fields: bool

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impl<'a, 'b> DebugStruct<'a, 'b>
where 'b: 'a,

1.2.0 · source

pub fn field( &mut self, name: &str, value: &dyn Debug, ) -> &mut DebugStruct<'a, 'b>

Adds a new field to the generated struct output.

§Examples
use std::fmt;

struct Bar {
    bar: i32,
    another: String,
}

impl fmt::Debug for Bar {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_struct("Bar")
           .field("bar", &self.bar) // We add `bar` field.
           .field("another", &self.another) // We add `another` field.
           // We even add a field which doesn't exist (because why not?).
           .field("nonexistent_field", &1)
           .finish() // We're good to go!
    }
}

assert_eq!(
    format!("{:?}", Bar { bar: 10, another: "Hello World".to_string() }),
    "Bar { bar: 10, another: \"Hello World\", nonexistent_field: 1 }",
);
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pub fn field_with<F>( &mut self, name: &str, value_fmt: F, ) -> &mut DebugStruct<'a, 'b>
where F: FnOnce(&mut Formatter<'_>) -> Result<(), Error>,

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

Adds a new field to the generated struct output.

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

1.53.0 · source

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

Marks the 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 Bar {
    bar: i32,
    hidden: f32,
}

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

assert_eq!(
    format!("{:?}", Bar { bar: 10, hidden: 1.0 }),
    "Bar { bar: 10, .. }",
);
1.2.0 · source

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

Finishes output and returns any error encountered.

§Examples
use std::fmt;

struct Bar {
    bar: i32,
    baz: String,
}

impl fmt::Debug for Bar {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_struct("Bar")
           .field("bar", &self.bar)
           .field("baz", &self.baz)
           .finish() // You need to call it to "finish" the
                     // struct formatting.
    }
}

assert_eq!(
    format!("{:?}", Bar { bar: 10, baz: "Hello World".to_string() }),
    "Bar { bar: 10, baz: \"Hello World\" }",
);

Trait Implementations§

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impl<'a, 'b> Visit for DebugStruct<'a, 'b>

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fn record_debug(&mut self, field: &Field, value: &dyn Debug)

Visit a value implementing fmt::Debug.
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fn record_f64(&mut self, field: &Field, value: f64)

Visit a double-precision floating point value.
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fn record_i64(&mut self, field: &Field, value: i64)

Visit a signed 64-bit integer value.
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fn record_u64(&mut self, field: &Field, value: u64)

Visit an unsigned 64-bit integer value.
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fn record_i128(&mut self, field: &Field, value: i128)

Visit a signed 128-bit integer value.
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fn record_u128(&mut self, field: &Field, value: u128)

Visit an unsigned 128-bit integer value.
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fn record_bool(&mut self, field: &Field, value: bool)

Visit a boolean value.
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fn record_str(&mut self, field: &Field, value: &str)

Visit a string value.
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fn record_bytes(&mut self, field: &Field, value: &[u8])

Visit a byte slice.
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impl<'a, 'b> Visit for DebugStruct<'a, 'b>

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fn record_debug(&mut self, field: &Field, value: &dyn Debug)

Visit a value implementing fmt::Debug.
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fn record_f64(&mut self, field: &Field, value: f64)

Visit a double-precision floating point value.
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fn record_i64(&mut self, field: &Field, value: i64)

Visit a signed 64-bit integer value.
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fn record_u64(&mut self, field: &Field, value: u64)

Visit an unsigned 64-bit integer value.
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fn record_i128(&mut self, field: &Field, value: i128)

Visit a signed 128-bit integer value.
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fn record_u128(&mut self, field: &Field, value: u128)

Visit an unsigned 128-bit integer value.
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fn record_bool(&mut self, field: &Field, value: bool)

Visit a boolean value.
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fn record_str(&mut self, field: &Field, value: &str)

Visit a string value.
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fn record_error(&mut self, field: &Field, value: &(dyn Error + 'static))

Records a type implementing Error. Read more

Auto Trait Implementations§

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

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

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

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

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

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impl<'a, 'b> !UnwindSafe for DebugStruct<'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> Az for T

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fn az<Dst>(self) -> Dst
where T: Cast<Dst>,

Casts the value.
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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<Src, Dst> CastFrom<Src> for Dst
where Src: Cast<Dst>,

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fn cast_from(src: Src) -> Dst

Casts the value.
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impl<T> CheckedAs for T

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fn checked_as<Dst>(self) -> Option<Dst>
where T: CheckedCast<Dst>,

Casts the value.
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impl<Src, Dst> CheckedCastFrom<Src> for Dst
where Src: CheckedCast<Dst>,

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fn checked_cast_from(src: Src) -> Option<Dst>

Casts the value.
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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> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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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> OverflowingAs for T

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fn overflowing_as<Dst>(self) -> (Dst, bool)
where T: OverflowingCast<Dst>,

Casts the value.
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impl<Src, Dst> OverflowingCastFrom<Src> for Dst
where Src: OverflowingCast<Dst>,

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fn overflowing_cast_from(src: Src) -> (Dst, bool)

Casts the value.
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impl<T> SaturatingAs for T

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fn saturating_as<Dst>(self) -> Dst
where T: SaturatingCast<Dst>,

Casts the value.
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impl<Src, Dst> SaturatingCastFrom<Src> for Dst
where Src: SaturatingCast<Dst>,

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fn saturating_cast_from(src: Src) -> Dst

Casts the value.
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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.
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impl<T> UnwrappedAs for T

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fn unwrapped_as<Dst>(self) -> Dst
where T: UnwrappedCast<Dst>,

Casts the value.
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impl<Src, Dst> UnwrappedCastFrom<Src> for Dst
where Src: UnwrappedCast<Dst>,

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fn unwrapped_cast_from(src: Src) -> Dst

Casts the value.
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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
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fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more
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impl<T> WrappingAs for T

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fn wrapping_as<Dst>(self) -> Dst
where T: WrappingCast<Dst>,

Casts the value.
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impl<Src, Dst> WrappingCastFrom<Src> for Dst
where Src: WrappingCast<Dst>,

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fn wrapping_cast_from(src: Src) -> Dst

Casts the value.