Enum Value

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pub enum Value<'host> {
    Unit,
    Tuple(Tuple<Value<'host>>),
    Borrow(&'host dyn Extern, Option<Rc<Value<'host>>>),
    Owned(Rc<dyn ExternOwned>, Option<Rc<Value<'host>>>),
    I64(i64),
    Bool(bool),
    String(Rc<str>),
    Function(Rc<Function<'host>>),
    EnumVariant(Rc<EnumVariant<'host>>),
    Option {
        contents: Option<Rc<Value<'host>>>,
        ty: ComplexType,
    },
    Mut(Mut<'host>),
    Type(Type),
}

Expand description

The root type of every espy value. All interoperation starts here.

Don’t be afraid to Clone this type; it contains only Copy types and Rcs.

Variants§

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Unit

Unit is the absense of a value. It can be thought of as both an empty tuple and an empty named tuple.

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Option

Fields

§contents: Option<Rc<Value<'host>>>

§ty: ComplexType

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Mut(Mut<'host>)

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Type(Type)

Implementations§

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impl<'host> Value<'host>

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pub fn to_static(&self) -> Option<StaticValue>

Returns None if self contains any Value::Borrow or Value::Mut.

Value::Borrow is not static for obvious reasons, and Value::Mut cannot be made static because of refcell subtyping. Instead, hosts using to_static should provide mutable state outside of the espy runtime.

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pub fn get(&self, index: i64) -> Result<Value<'host>, Error>

Convenience method for indexing values of various types by an integer.

Usually this is most useful for reading function arguments by index, which are passed as a tuple by convention.

§Errors

Returns ErrorKind::IndexNotFound if self cannot be indexed or the index is out of range for the container.

Extern and ExternOwned implementations may return arbitary errors.

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pub fn find(&self, index: Rc<str>) -> Result<Value<'host>, Error>

Convenience methods for indexing values of various types by a string.

§Errors

Returns Error::index_not_found if self cannot be indexed or the index is not found in the container.

Value::Borrow and Value::Owned implementations may return arbitary errors.

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pub fn index( &self, index: impl Into<Value<'host>>, ) -> Result<Value<'host>, Error>

Convenience methods for indexing values of various types.

§Errors

Returns Error::index_not_found if self cannot be indexed or the index is not found in the container.

Value::Borrow and Value::Owned implementations may return arbitary errors.

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pub fn downcast_extern<T>(&self) -> Option<&T>
where T: Any,

Attempts to downcast instances of Value::Borrow and Value::Owned into &T.

Note that Extern and ExternOwned implementations have to opt into this behavior by implementing their any functions. The default any implementation will result in this function returning None.

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pub fn eq(self, other: Value<'host>) -> Result<bool, Error>

§Errors

Returns an error if self and other are incomparable.

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pub fn type_of(&self) -> Result<ComplexType, Error>

§Errors

Returns an error if a mutable reference is being mutably borrowed.

This can be safely ignored by the host if it has not deliberately borrowed an espy value.

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pub fn concat(self, r: Value<'host>) -> Value<'host>

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pub fn borrow(external: &'host dyn Extern) -> Value<'host>

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pub fn owned(external: Rc<dyn ExternOwned>) -> Value<'host>

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impl<'host> Value<'host>

TryInto shortcuts

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pub fn into_unit(self) -> Result<(), Error>

§Errors

Returns an error if self is not a Value::Unit

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pub fn into_tuple(self) -> Result<Tuple<Value<'host>>, Error>

§Errors

Returns an error if self is not a Value::Tuple

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pub fn into_vec(self) -> Vec<Value<'host>>

Turns this value into a vector of values.

Value::Tuple’s members will be collected into the vector. Value::Unit will produce an empty vector. All other variants will produce a vector with just one member.

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