pub struct DebugMap<'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 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}",
);
Implementations§
source§impl<'a, 'b> DebugMap<'a, 'b>where
'b: 'a,
impl<'a, 'b> DebugMap<'a, 'b>where 'b: 'a,
sourcepub fn entry(
&mut self,
key: &dyn Debug,
value: &dyn Debug
) -> &mut DebugMap<'a, 'b>
Available on non-crate feature miri-test-libstd
only.
pub fn entry( &mut self, key: &dyn Debug, value: &dyn Debug ) -> &mut DebugMap<'a, 'b>
miri-test-libstd
only.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)]}",
);
1.42.0 · sourcepub fn key(&mut self, key: &dyn Debug) -> &mut DebugMap<'a, 'b>
Available on non-crate feature miri-test-libstd
only.
pub fn key(&mut self, key: &dyn Debug) -> &mut DebugMap<'a, 'b>
miri-test-libstd
only.Adds the key part of a new entry to the map output.
This method, together with value
, is an alternative to entry
that
can be used when the complete entry isn’t known upfront. Prefer the entry
method when it’s possible to use.
Panics
key
must be called before value
and each call to key
must be followed
by a corresponding call to value
. Otherwise this method will panic.
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()
.key(&"whole").value(&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)]}",
);
1.42.0 · sourcepub fn value(&mut self, value: &dyn Debug) -> &mut DebugMap<'a, 'b>
Available on non-crate feature miri-test-libstd
only.
pub fn value(&mut self, value: &dyn Debug) -> &mut DebugMap<'a, 'b>
miri-test-libstd
only.Adds the value part of a new entry to the map output.
This method, together with key
, is an alternative to entry
that
can be used when the complete entry isn’t known upfront. Prefer the entry
method when it’s possible to use.
Panics
key
must be called before value
and each call to key
must be followed
by a corresponding call to value
. Otherwise this method will panic.
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()
.key(&"whole").value(&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)]}",
);
sourcepub fn entries<K, V, I>(&mut self, entries: I) -> &mut DebugMap<'a, 'b>where
K: Debug,
V: Debug,
I: IntoIterator<Item = (K, V)>,
Available on non-crate feature miri-test-libstd
only.
pub fn entries<K, V, I>(&mut self, entries: I) -> &mut DebugMap<'a, 'b>where K: Debug, V: Debug, I: IntoIterator<Item = (K, V)>,
miri-test-libstd
only.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}",
);
sourcepub fn finish(&mut self) -> Result<(), Error>
Available on non-crate feature miri-test-libstd
only.
pub fn finish(&mut self) -> Result<(), Error>
miri-test-libstd
only.Finishes output and returns any error encountered.
Panics
key
must be called before value
and each call to key
must be followed
by a corresponding call to value
. Otherwise this method will panic.
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}",
);
Trait Implementations§
§impl<'a, 'b> Visit for DebugMap<'a, 'b>
impl<'a, 'b> Visit for DebugMap<'a, 'b>
§fn record_debug(&mut self, field: &Field, value: &dyn Debug)
fn record_debug(&mut self, field: &Field, value: &dyn Debug)
fmt::Debug
.§fn record_f64(&mut self, field: &Field, value: f64)
fn record_f64(&mut self, field: &Field, value: f64)
§fn record_i64(&mut self, field: &Field, value: i64)
fn record_i64(&mut self, field: &Field, value: i64)
§fn record_u64(&mut self, field: &Field, value: u64)
fn record_u64(&mut self, field: &Field, value: u64)
§fn record_i128(&mut self, field: &Field, value: i128)
fn record_i128(&mut self, field: &Field, value: i128)
§fn record_u128(&mut self, field: &Field, value: u128)
fn record_u128(&mut self, field: &Field, value: u128)
§fn record_bool(&mut self, field: &Field, value: bool)
fn record_bool(&mut self, field: &Field, value: bool)
§fn record_str(&mut self, field: &Field, value: &str)
fn record_str(&mut self, field: &Field, value: &str)
§fn record_error(&mut self, field: &Field, value: &(dyn Error + 'static))
fn record_error(&mut self, field: &Field, value: &(dyn Error + 'static))
std
only.Error
.