Struct core::fmt::DebugStruct  1.2.0[−][src]
pub struct DebugStruct<'a, 'b: 'a> { /* fields omitted */ }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 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() }),
    "Foo { bar: 10, baz: \"Hello World\" }",
);Implementations
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("not_existing_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\", not_existing_field: 1 }",
);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\" }",
);