zng::var

Trait IntoVar

pub trait IntoVar<T>where
    T: VarValue,{
    type Var: Var<T>;

    // Required method
    fn into_var(self) -> Self::Var;

    // Provided method
    fn into_boxed_var(self) -> Box<dyn VarBoxed<T>>
       where Self: Sized { ... }
}

Expand description

A value-to-var conversion that consumes the value.

Every Var<T> implements this to convert to itself, every VarValue implements this to convert to a LocalVar<T>.

This trait is used by most properties, it allows then to accept literal values, variables and context variables all with a single signature. Together with Var<T> this gives properties great flexibility of usage, at zero-cost. Widget when blocks also use IntoVar<T> to support changing the property value depending on the widget state.

Value types can also manually implement this to support a shorthand literal syntax for when they are used in properties, this converts the shorthand value like a tuple into the actual value type and wraps it into a variable, usually LocalVar too. They can implement the trait multiple times to support different shorthand syntaxes or different types in the shorthand value.

Required Associated Types§

source

type Var: Var<T>

Variable type that will wrap the T value.

This is the LocalVar for most types or Self for variable types.

Required Methods§

source

fn into_var(self) -> Self::Var

Converts the source value into a var.

Provided Methods§

source

fn into_boxed_var(self) -> Box<dyn VarBoxed<T>>
where Self: Sized,

Converts into BoxedVar<T>.

This method exists to help the type system infer the type in this scenario:

fn foo(foo: impl IntoVar<bool>) { }

foo(if bar {
    BAR_VAR.map(|b| !*b).boxed()
} else {
    true.into_boxed_var()
});

We need a BoxedVar<bool> to unify the input types that can be a map var or a LocalVar<bool>. Writing true.into_var().boxed() causes the type inference to fail, requiring us to write IntoVar::<bool>::into_var(true).boxed().

Trait IntoVarCopy item path

Required Associated Types§

type Var: Var<T>

Required Methods§

fn into_var(self) -> Self::Var

Provided Methods§

fn into_boxed_var(self) -> Box<dyn VarBoxed<T>>where Self: Sized,

Implementations on Foreign Types§

impl IntoVar<GradientStop> for f32

fn into_var(self) -> <f32 as IntoVar<GradientStop>>::Var

type Var = LocalVar<GradientStop>

impl IntoVar<GradientStop> for i32

fn into_var(self) -> <i32 as IntoVar<GradientStop>>::Var

type Var = LocalVar<GradientStop>

impl IntoVar<SaveState> for bool

fn into_var(self) -> <bool as IntoVar<SaveState>>::Var

type Var = LocalVar<SaveState>

impl IntoVar<DragDropData> for &'static str

type Var = LocalVar<DragDropData>

fn into_var(self) -> <&'static str as IntoVar<DragDropData>>::Var

impl IntoVar<DragDropData> for String

type Var = LocalVar<DragDropData>

fn into_var(self) -> <String as IntoVar<DragDropData>>::Var

impl IntoVar<DragDropData> for PathBuf

type Var = LocalVar<DragDropData>

fn into_var(self) -> <PathBuf as IntoVar<DragDropData>>::Var

impl IntoVar<CommandScope> for &'static str

fn into_var(self) -> <&'static str as IntoVar<CommandScope>>::Var

type Var = LocalVar<CommandScope>

impl IntoVar<FontColorPalette> for u16

type Var = LocalVar<FontColorPalette>

fn into_var(self) -> <u16 as IntoVar<FontColorPalette>>::Var

impl IntoVar<FontStyleSet> for u8

type Var = LocalVar<FontStyleSet>

fn into_var(self) -> <u8 as IntoVar<FontStyleSet>>::Var

impl IntoVar<GlyphSource> for &'static str

type Var = LocalVar<GlyphSource>

fn into_var(self) -> <&'static str as IntoVar<GlyphSource>>::Var

impl IntoVar<GlyphSource> for char

type Var = LocalVar<GlyphSource>

fn into_var(self) -> <char as IntoVar<GlyphSource>>::Var

impl IntoVar<ImageDownscale> for Size2D<Px, Px>

type Var = LocalVar<ImageDownscale>

fn into_var(self) -> <Size2D<Px, Px> as IntoVar<ImageDownscale>>::Var

impl IntoVar<ImageRepeat> for bool

type Var = LocalVar<ImageRepeat>

fn into_var(self) -> <bool as IntoVar<ImageRepeat>>::Var

impl IntoVar<ImageSource> for &'static [u8]

fn into_var(self) -> <&'static [u8] as IntoVar<ImageSource>>::Var ⓘ

type Var = LocalVar<ImageSource>

impl IntoVar<ImageSource> for &str

fn into_var(self) -> <&str as IntoVar<ImageSource>>::Var

type Var = LocalVar<ImageSource>

impl IntoVar<ImageSource> for &Path

type Var = LocalVar<ImageSource>

fn into_var(self) -> <&Path as IntoVar<ImageSource>>::Var

impl IntoVar<ImageSource> for (Uri, &'static str)

fn into_var(self) -> <(Uri, &'static str) as IntoVar<ImageSource>>::Var

type Var = LocalVar<ImageSource>

impl IntoVar<ImageSource> for String

fn into_var(self) -> <String as IntoVar<ImageSource>>::Var

type Var = LocalVar<ImageSource>

impl IntoVar<ImageSource> for Arc<Vec<u8>>

fn into_var(self) -> <Arc<Vec<u8>> as IntoVar<ImageSource>>::Var ⓘ

type Var = LocalVar<ImageSource>

impl IntoVar<ImageSource> for Vec<u8>

fn into_var(self) -> <Vec<u8> as IntoVar<ImageSource>>::Var ⓘ

type Var = LocalVar<ImageSource>

impl IntoVar<ImageSource> for PathBuf

type Var = LocalVar<ImageSource>

fn into_var(self) -> <PathBuf as IntoVar<ImageSource>>::Var

impl IntoVar<L10nArgument> for &'static str

type Var = LocalVar<L10nArgument>

fn into_var(self) -> <&'static str as IntoVar<L10nArgument>>::Var

impl IntoVar<L10nArgument> for bool

type Var = LocalVar<L10nArgument>

fn into_var(self) -> <bool as IntoVar<L10nArgument>>::Var

impl IntoVar<L10nArgument> for char

type Var = LocalVar<L10nArgument>

fn into_var(self) -> <char as IntoVar<L10nArgument>>::Var

Trait IntoVar

fn into_boxed_var(self) -> Box<dyn VarBoxed<T>>
where Self: Sized,