Struct ctxmap::CtxMapView

pub struct CtxMapView<'a, S: Schema>(_);

Mutable reference to CtxMap where the value has changed.

Use CtxMapViwe instead of &mut CtxMap because &mut CtxMap, whose value has been changed, will be broken if std::mem::swap is used.

Implementations

impl<'a, S: Schema> CtxMapView<'a, S>

pub fn with<T: ?Sized + 'static, U>(
    &mut self,
    key: &'static Key<S, T>,
    value: &T,
    f: impl FnOnce(&mut CtxMapView<'_, S>) -> U
) -> U

Sets a value to CtxMap only while f is being called.

Example

ctxmap::schema!(S);
ctxmap::key!(S { KEY_A: u16 = 20 });

let mut m = ctxmap::CtxMap::new();
assert_eq!(m[&KEY_A], 20);
m.with(&KEY_A, &30, |m| {
    assert_eq!(m[&KEY_A], 30);
    m.with(&KEY_A, &40, |m| {
       assert_eq!(m[&KEY_A], 40);
   });
   assert_eq!(m[&KEY_A], 30);
});
assert_eq!(m[&KEY_A], 20);

pub fn viwe(&mut self) -> CtxMapView<'_, S>

Return CtxMapView with modified lifetime.

Methods from Deref<Target = CtxMap<S>>

pub fn get<T: ?Sized>(&self, key: &'static Key<S, T>) -> Option<&T>

Returns a reference to the value corresponding to the key.

Example

ctxmap::schema!(S);
ctxmap::key!(S { KEY_A: u16 });

let mut m = ctxmap::CtxMap::new();
assert_eq!(m.get(&KEY_A), None);
m.with(&KEY_A, &10, |m| {
    assert_eq!(m.get(&KEY_A), Some(&10));
});
assert_eq!(m.get(&KEY_A), None);

Trait Implementations

impl<'a, S: Schema> Deref for CtxMapView<'a, S>

type Target = CtxMap<S>

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.