Struct std::fmt::DebugStruct
1.2.0 · source · pub struct DebugStruct<'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 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\" }",
);
RunImplementations§
source§impl<'a, 'b> DebugStruct<'a, 'b>where
'b: 'a,
impl<'a, 'b> DebugStruct<'a, 'b>where
'b: 'a,
sourcepub fn field(
&mut self,
name: &str,
value: &dyn Debug
) -> &mut DebugStruct<'a, 'b>
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 }",
);
Runsourcepub fn field_with<F>(
&mut self,
name: &str,
value_fmt: F
) -> &mut DebugStruct<'a, 'b>
🔬This is a nightly-only experimental API. (debug_closure_helpers
#117729)
pub fn field_with<F>( &mut self, name: &str, value_fmt: F ) -> &mut DebugStruct<'a, 'b>
debug_closure_helpers
#117729)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 · sourcepub fn finish_non_exhaustive(&mut self) -> Result<(), Error>
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, .. }",
);
Runsourcepub fn finish(&mut self) -> Result<(), Error>
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\" }",
);
RunAuto Trait Implementations§
impl<'a, 'b> !RefUnwindSafe for DebugStruct<'a, 'b>
impl<'a, 'b> !Send for DebugStruct<'a, 'b>
impl<'a, 'b> !Sync for DebugStruct<'a, 'b>
impl<'a, 'b> Unpin for DebugStruct<'a, 'b>
impl<'a, 'b> !UnwindSafe for DebugStruct<'a, 'b>
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more