Struct DebugStruct 

pub struct DebugStruct<'a, 'b>
where
    'b: 'a,
{ /* private fields */ }

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() }),
    r#"Foo { bar: 10, baz: "Hello World" }"#,
);

Implementations

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

where 'b: 'a,

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() }),
    r#"Bar { bar: 10, another: "Hello World", nonexistent_field: 1 }"#,
);

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.

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, .. }",
);

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() }),
    r#"Bar { bar: 10, baz: "Hello World" }"#,
);

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 16 bytes