Struct NullDatamodel 

pub struct NullDatamodel;

The null datamodel: no data, and only In('id') conditions. Every other condition, value expression, assignment, script and foreach is an evaluation error. Inline content (of <content>) is not an expression and is passed through as a string.

Implementations

impl NullDatamodel

pub fn new() -> Self

A new null datamodel.

Trait Implementations

impl Clone for NullDatamodel

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for NullDatamodel

impl Datamodel for NullDatamodel

fn snapshot(&self) -> Value

The null datamodel has no state: its snapshot is the empty value (undefined).

fn name(&self) -> &str

The datamodel name as used in the datamodel attribute.

fn init_session(&mut self, _info: &SessionInfo) -> Result<(), EvalError>

Prepare a fresh session: set the system variables _sessionid, _name and _ioprocessors. Called once before any other operation.

fn set_environment(&mut self, _env: &Environment)

Set the sources of nondeterminism for the input about to be processed.

fn declare(&mut self, _id: &str) -> Result<(), EvalError>

Create a data item with an undefined value.

fn set_event(&mut self, _event: &Event)

Bind _event to the event currently being processed.

fn eval_cond( &mut self, expr: &str, states: &dyn StateQuery, ) -> Result<bool, EvalError>

Evaluate a condition. Must not change the datamodel ([[openspec:datamodel#Guard Purity]]).

fn eval_value( &mut self, _expr: &str, _states: &dyn StateQuery, ) -> Result<Value, EvalError>

Evaluate a value expression.

fn eval_content(&mut self, content: &str) -> Result<Value, EvalError>

Interpret inline content (of <data>, <assign>, <content>) as a value.

fn assign_expr( &mut self, _location: &str, _expr: &str, _states: &dyn StateQuery, ) -> Result<(), EvalError>

Assign the value of an expression to a location (<assign location expr>).

fn assign_value( &mut self, _location: &str, _value: Value, ) -> Result<(), EvalError>

Assign a value to a location. The location must already exist.

fn bind_var(&mut self, _name: &str, _value: Value) -> Result<(), EvalError>

Bind a variable, declaring it when it does not exist (used by foreach item and index).

fn is_location(&mut self, _location: &str) -> bool

Whether location is a legal, existing location (used by foreach and idlocation).

fn exec_script( &mut self, _script: &str, _states: &dyn StateQuery, ) -> Result<(), EvalError>

Execute a script.

fn foreach_items( &mut self, _array: &str, _states: &dyn StateQuery, ) -> Result<Vec<Value>, EvalError>

Evaluate a foreach array expression to its items, shallow-copied, in index order.

fn restore(&mut self, snapshot: &Value) -> Result<(), EvalError>

Restore a state produced by Datamodel::snapshot.

fn check_event(&self, _event: &Event) -> Result<(), EvalError>

Whether event’s payload has the type the chart declares for it. A datamodel without declared event types accepts every payload (the default). The interpreter does not call this: a host calls it, through admit, before it hands an event to the session.

impl Debug for NullDatamodel

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for NullDatamodel

fn default() -> Self

Returns the “default value” for a type.

impl Eq for NullDatamodel

impl PartialEq for NullDatamodel

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for NullDatamodel