Struct libdata::column::Value

pub struct Value(_);

A column value.

The value represents some bit of information. It is an abstract handle, meaning the concrete type is not known from the outside. It is possible to ask it for its type identity, so it's possible to find out if two values are of the same type or ask if it is of a specific type. It is possible to get access to the typed data (if the type is known and matches), but it should be used only when necessary. Prefer the generic handling when possible.

However, it implements a lot of traits that allow for manipulation in generic manner.

This allows tagging flows with data without knowing the types of information used to tag it upfront.

Note that the values act sane in regards to the normal traits. Eg. the Ord implementation can compare even values of different underlying types.

Methods

impl Value

fn ident(&self) -> Ident

Provides the identity of the column type.

fn downcast_ref<T: 'static>(&self) -> Option<&T>

Tries to turn the value into the type held inside.

This allows accessing the data held inside as the type it actually is. It returns None if the requested type doesn't match the actual one.

Generally, you should use this only if you know the type. Most of the handling can be done in a generic way, without extracting the data inside.

Trait Implementations

impl Clone for Value

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Value

fn fmt(&self, f: &mut Formatter) -> FmtResult

Formats the value using the given formatter.

impl Eq for Value

impl<C: Type> From<C> for Value

fn from(c: C) -> Self

Performs the conversion.

impl Ord for Value

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

🔬 This is a nightly-only experimental API. (ord_max_min)

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

🔬 This is a nightly-only experimental API. (ord_max_min)

Compares and returns the minimum of two values.

impl PartialEq for Value

fn eq(&self, other: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialOrd for Value

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Serialize for Value

fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error>

Serialize this value into the given Serde serializer.