Struct DebugList 

pub struct DebugList<'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 list of items as a part of your Debug::fmt implementation.

This can be constructed by the Formatter::debug_list method.

Examples

use std::fmt;

struct Foo(Vec<i32>);

impl fmt::Debug for Foo {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_list().entries(self.0.iter()).finish()
    }
}

assert_eq!(
    format!("{:?}", Foo(vec![10, 11])),
    "[10, 11]",
);

Implementations

impl<'a, 'b> DebugList<'a, 'b>

where 'b: 'a,

pub fn entry(&mut self, entry: &dyn Debug) -> &mut DebugList<'a, 'b>

Adds a new entry to the list output.

Examples

use std::fmt;

struct Foo(Vec<i32>, Vec<u32>);

impl fmt::Debug for Foo {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_list()
           .entry(&self.0) // We add the first "entry".
           .entry(&self.1) // We add the second "entry".
           .finish()
    }
}

assert_eq!(
    format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
    "[[10, 11], [12, 13]]",
);

pub fn entry_with<F>(&mut self, entry_fmt: F) -> &mut DebugList<'a, 'b>

where F: FnOnce(&mut Formatter<'_>) -> Result<(), Error>,

🔬This is a nightly-only experimental API. (debug_closure_helpers)

Adds a new entry to the list output.

This method is equivalent to DebugList::entry, but formats the entry using a provided closure rather than by calling Debug::fmt.

pub fn entries<D, I>(&mut self, entries: I) -> &mut DebugList<'a, 'b>

where D: Debug, I: IntoIterator<Item = D>,

Adds the contents of an iterator of entries to the list output.

Examples

use std::fmt;

struct Foo(Vec<i32>, Vec<u32>);

impl fmt::Debug for Foo {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_list()
           .entries(self.0.iter())
           .entries(self.1.iter())
           .finish()
    }
}

assert_eq!(
    format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
    "[10, 11, 12, 13]",
);

pub fn finish_non_exhaustive(&mut self) -> Result<(), Error>

Marks the list as non-exhaustive, indicating to the reader that there are some other elements that are not shown in the debug representation.

Examples

use std::fmt;

struct Foo(Vec<i32>);

impl fmt::Debug for Foo {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        // Print at most two elements, abbreviate the rest
        let mut f = fmt.debug_list();
        let mut f = f.entries(self.0.iter().take(2));
        if self.0.len() > 2 {
            f.finish_non_exhaustive()
        } else {
            f.finish()
        }
    }
}

assert_eq!(
    format!("{:?}", Foo(vec![1, 2, 3, 4])),
    "[1, 2, ..]",
);

pub fn finish(&mut self) -> Result<(), Error>

Finishes output and returns any error encountered.

Examples

use std::fmt;

struct Foo(Vec<i32>);

impl fmt::Debug for Foo {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt.debug_list()
           .entries(self.0.iter())
           .finish() // Ends the list formatting.
    }
}

assert_eq!(
    format!("{:?}", Foo(vec![10, 11])),
    "[10, 11]",
);

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