Struct macro_tools::attr_prop::AttributePropertyOptionalSingletone

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pub struct AttributePropertyOptionalSingletone<Marker = AttributePropertyOptionalSingletoneMarker>(/* private fields */);

Expand description

A generic attribute property for switching on/off. Has 3 states: None, Some( true ), Some( false ). Defaults to None.

Unlike AttributePropertyOptionalBoolean, it “understands” on, off keywords during parsing. For example: #[ attribute( on ) ] and #[ attribute( off )]. As a consequence, the property has two keywords.

Implementations§

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impl<Marker> AttributePropertyOptionalSingletone<Marker>

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pub fn value(self, default: bool) -> bool

Return bool value: on/off, use argument as default if it’s None.

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pub fn internal(self) -> Option<bool>

Unwraps and returns the internal optional boolean value.

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pub fn ref_internal(&self) -> Option<&bool>

Returns a reference to the internal optional boolean value.

Methods from Deref<Target = Option<bool>>§

1.0.0 · source

pub fn is_some(&self) -> bool

Returns true if the option is a Some value.

§Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_some(), true);

let x: Option<u32> = None;
assert_eq!(x.is_some(), false);

1.0.0 · source

pub fn is_none(&self) -> bool

Returns true if the option is a None value.

§Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_none(), false);

let x: Option<u32> = None;
assert_eq!(x.is_none(), true);

1.0.0 · source

pub fn as_ref(&self) -> Option<&T>

Converts from &Option<T> to Option<&T>.

§Examples

Calculates the length of an Option<String> as an Option<usize> without moving the String. The map method takes the self argument by value, consuming the original, so this technique uses as_ref to first take an Option to a reference to the value inside the original.

let text: Option<String> = Some("Hello, world!".to_string());
// First, cast `Option<String>` to `Option<&String>` with `as_ref`,
// then consume *that* with `map`, leaving `text` on the stack.
let text_length: Option<usize> = text.as_ref().map(|s| s.len());
println!("still can print text: {text:?}");

1.33.0 · source

pub fn as_pin_ref(self: Pin<&Option<T>>) -> Option<Pin<&T>>

Converts from Pin<&Option<T>> to Option<Pin<&T>>.

1.33.0 · source

pub fn as_pin_mut(self: Pin<&mut Option<T>>) -> Option<Pin<&mut T>>

Converts from Pin<&mut Option<T>> to Option<Pin<&mut T>>.

1.75.0 · source

pub fn as_slice(&self) -> &[T]

Returns a slice of the contained value, if any. If this is None, an empty slice is returned. This can be useful to have a single type of iterator over an Option or slice.

Note: Should you have an Option<&T> and wish to get a slice of T, you can unpack it via opt.map_or(&[], std::slice::from_ref).

§Examples

assert_eq!(
    [Some(1234).as_slice(), None.as_slice()],
    [&[1234][..], &[][..]],
);

The inverse of this function is (discounting borrowing) [_]::first:

for i in [Some(1234_u16), None] {
    assert_eq!(i.as_ref(), i.as_slice().first());
}

1.40.0 · source

pub fn as_deref(&self) -> Option<&<T as Deref>::Target>
where T: Deref,

Converts from Option<T> (or &Option<T>) to Option<&T::Target>.

Leaves the original Option in-place, creating a new one with a reference to the original one, additionally coercing the contents via Deref.

§Examples

let x: Option<String> = Some("hey".to_owned());
assert_eq!(x.as_deref(), Some("hey"));

let x: Option<String> = None;
assert_eq!(x.as_deref(), None);

1.0.0 · source

pub fn iter(&self) -> Iter<'_, T>

Returns an iterator over the possibly contained value.

§Examples

let x = Some(4);
assert_eq!(x.iter().next(), Some(&4));

let x: Option<u32> = None;
assert_eq!(x.iter().next(), None);

Trait Implementations§

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impl<Marker> AsRef<Option<bool>> for AttributePropertyOptionalSingletone<Marker>

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fn as_ref(&self) -> &Option<bool>

Converts this type into a shared reference of the (usually inferred) input type.

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impl<Marker, IntoT> Assign<AttributePropertyOptionalSingletone<Marker>, IntoT> for AttributePropertyOptionalSingletone<Marker>
where IntoT: Into<AttributePropertyOptionalSingletone<Marker>>,

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fn assign(&mut self, component: IntoT)

Inserts value of another instance into the option if it is None, then returns a mutable reference to the contained value. If another instance does is None then do nothing.

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fn impute(self, component: IntoT) -> Self
where Self: Sized,

Sets or replaces the component on the object with the given value. Unlike function (assing) function (impute) also consumes self and return it what is useful for builder pattern.

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