DebugStruct in std::fmt - Rust (original) (raw)
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 yourDebug::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\" }",
);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 }",
);🔬This is a nightly-only experimental API. (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 · source
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, .. }",
);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\" }",
);Returns the argument unchanged.
Calls U::from(self).
That is, this conversion is whatever the implementation of[From](../convert/trait.From.html "trait std::convert::From")<T> for U chooses to do.
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.