1.2.0[−][src]Struct alloc::fmt::DebugMap
A struct to help with fmt::Debug
implementations.
This is useful when you wish to output a formatted map as a part of your
Debug::fmt
implementation.
This can be constructed by the
Formatter::debug_map
method.
Examples
use std::fmt; struct Foo(Vec<(String, i32)>); impl fmt::Debug for Foo { fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result { fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish() } } assert_eq!( format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])), "{\"A\": 10, \"B\": 11}", );
Methods
impl<'a, 'b> DebugMap<'a, 'b> where
'b: 'a,
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'b: 'a,
pub fn entry(
&mut self,
key: &dyn Debug,
value: &dyn Debug
) -> &mut DebugMap<'a, 'b>
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&mut self,
key: &dyn Debug,
value: &dyn Debug
) -> &mut DebugMap<'a, 'b>
Adds a new entry to the map output.
Examples
use std::fmt; struct Foo(Vec<(String, i32)>); impl fmt::Debug for Foo { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_map() .entry(&"whole", &self.0) // We add the "whole" entry. .finish() } } assert_eq!( format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])), "{\"whole\": [(\"A\", 10), (\"B\", 11)]}", );
pub fn entries<K, V, I>(&mut self, entries: I) -> &mut DebugMap<'a, 'b> where
I: IntoIterator<Item = (K, V)>,
K: Debug,
V: Debug,
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I: IntoIterator<Item = (K, V)>,
K: Debug,
V: Debug,
Adds the contents of an iterator of entries to the map output.
Examples
use std::fmt; struct Foo(Vec<(String, i32)>); impl fmt::Debug for Foo { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_map() // We map our vec so each entries' first field will become // the "key". .entries(self.0.iter().map(|&(ref k, ref v)| (k, v))) .finish() } } assert_eq!( format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])), "{\"A\": 10, \"B\": 11}", );
pub fn finish(&mut self) -> Result<(), Error>
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Finishes output and returns any error encountered.
Examples
use std::fmt; struct Foo(Vec<(String, i32)>); impl fmt::Debug for Foo { fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { fmt.debug_map() .entries(self.0.iter().map(|&(ref k, ref v)| (k, v))) .finish() // Ends the struct formatting. } } assert_eq!( format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])), "{\"A\": 10, \"B\": 11}", );
Auto Trait Implementations
Blanket Implementations
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T> From<T> for T
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,