morph::forms::RuleExpr Class Reference

One x-rules entry, or a condition inside one, and its translation into expr/1. More...

#include <rules.hpp>

Public Types
enum class	Kind : std::uint8_t {   Engaged , NotEngaged , Equals , Greater ,   GreaterOrEqual , Less , LessOrEqual , RequiredWhen ,   ExactlyOneOf , AtLeastOneOf , MutuallyExclusive , VisibleWhen ,   ReadonlyWhen , And , Or , Not ,   Unknown }
	The rule kinds. More...

Public Member Functions
Kind	kind () const noexcept
	The kind.
std::string_view	kindName () const noexcept
	The kind as the schema spells it.
std::span< std::string const >	fields () const noexcept
	The fields this node names directly (fields).
bool	names (std::string_view field) const noexcept
	Whether this node names field directly. A presentation rule applies to every field it names.
RuleExpr const *	when () const noexcept
	The when clause of requiredWhen, visibleWhen and readonlyWhen.
std::span< RuleExpr const >	conditions () const noexcept
	The operands of and and or, or the one operand of not.
bool	gates () const noexcept
	Whether the rule decides readiness. visibleWhen and readonlyWhen only present.
bool	presents (Kind kind, std::string_view field) const noexcept
	Whether the rule is a presentation rule of kind that names field.
detail::engine::Json const &	expression () const noexcept
	The translation, as expr/1 JSON: for a gating rule its test, for a presentation rule its when clause. Set on a node parse returned; a child node holds none.
std::span< std::string const >	operands () const noexcept
	The wire names the translation reads, by operand index (f0 is the first).
Tri	evaluate (RuleLookup const &lookup) const
	Evaluates the translation with the UI document's evaluator.
Tri	whenHolds (RuleLookup const &lookup) const
	Evaluates the when clause of a requiredWhen, visibleWhen or readonlyWhen.

Static Public Member Functions
static std::expected< RuleExpr, SchemaError >	parse (detail::engine::Json const &node, std::string const &path)
	Reads one rule or condition node and translates it.

Detailed Description

One x-rules entry, or a condition inside one, and its translation into expr/1.

The 16 kinds the emitters write are read; any other kind parses and is Unknown, so an older client never refuses a newer server's form. A rule's operands are numbered f0, f1, … in its translation, and each operand reads as two names: fN.engaged (true, false, or null when its draft does not encode) and fN.value (the encoded value, null unless it is valid). The two are needed because a blank operand and an invalid one are both "no value" to the expression language, and the rules tell them apart: a comparison with a blank operand holds vacuously, one with an invalid operand is Unknown.

Definition at line 191 of file rules.hpp.

Member Enumeration Documentation

Kind

enum class morph::forms::RuleExpr::Kind : std::uint8_t

strong

The rule kinds.

Enumerator
Engaged	engaged: the field has a value.
NotEngaged	notEngaged.
Equals	equals: the field equals the literal value (valueText for wide integers).
Greater	greater: the first field is greater than the second, when both are engaged.
GreaterOrEqual	greaterOrEqual.
Less	less.
LessOrEqual	lessOrEqual.
RequiredWhen	requiredWhen: the fields are required while when holds.
ExactlyOneOf	exactlyOneOf: exactly one field is engaged.
AtLeastOneOf	atLeastOneOf.
MutuallyExclusive	mutuallyExclusive: at most one field is engaged.
VisibleWhen	visibleWhen: presentation; the fields are shown while when holds.
ReadonlyWhen	readonlyWhen: presentation; the fields are frozen while when holds.
And	and over conditions.
Or	or over conditions.
Not	not of condition.
Unknown	A kind this engine does not know.

Definition at line 194 of file rules.hpp.

Member Function Documentation

parse()

std::expected< RuleExpr, SchemaError > morph::forms::RuleExpr::parse ( detail::engine::Json const & node, std::string const & path )

inlinestaticnodiscard

Reads one rule or condition node and translates it.

Parameters

node	The node.
path	Where it is, for errors.

Returns

The rule, or why it does not read: a node that is not an object, a missing kind, a malformed fields, a known kind without the operands it needs, or a translation larger than expr/1 admits.

Definition at line 219 of file rules.hpp.

kind()

Kind morph::forms::RuleExpr::kind ( ) const

inlinenodiscardnoexcept

The kind.

Returns

The kind; Unknown for a kind this engine does not know.

Definition at line 241 of file rules.hpp.

kindName()

std::string_view morph::forms::RuleExpr::kindName ( ) const

inlinenodiscardnoexcept

The kind as the schema spells it.

Returns

The kind string.

Definition at line 245 of file rules.hpp.

fields()

std::span< std::string const > morph::forms::RuleExpr::fields ( ) const

inlinenodiscardnoexcept

The fields this node names directly (fields).

Returns

The wire names.

Definition at line 249 of file rules.hpp.

names()

bool morph::forms::RuleExpr::names ( std::string_view field ) const

inlinenodiscardnoexcept

Whether this node names field directly. A presentation rule applies to every field it names.

Parameters

field

The wire name.

Returns

Whether it is among fields().

Definition at line 254 of file rules.hpp.

when()

RuleExpr const * morph::forms::RuleExpr::when ( ) const

inlinenodiscardnoexcept

The when clause of requiredWhen, visibleWhen and readonlyWhen.

Returns

The clause, or null for any other kind.

Definition at line 260 of file rules.hpp.

conditions()

std::span< RuleExpr const > morph::forms::RuleExpr::conditions ( ) const

inlinenodiscardnoexcept

The operands of and and or, or the one operand of not.

Returns

The child conditions; empty for any other kind.

Definition at line 267 of file rules.hpp.

gates()

bool morph::forms::RuleExpr::gates ( ) const

inlinenodiscardnoexcept

Whether the rule decides readiness. visibleWhen and readonlyWhen only present.

Returns

false for the presentation kinds.

Definition at line 274 of file rules.hpp.

presents()

bool morph::forms::RuleExpr::presents ( Kind kind, std::string_view field ) const

inlinenodiscardnoexcept

Whether the rule is a presentation rule of kind that names field.

Parameters

kind	RequiredWhen, VisibleWhen or ReadonlyWhen.
field	The wire name.

Returns

Whether it applies to the field's presentation.

Definition at line 280 of file rules.hpp.

expression()

detail::engine::Json const & morph::forms::RuleExpr::expression ( ) const

inlinenodiscardnoexcept

The translation, as expr/1 JSON: for a gating rule its test, for a presentation rule its when clause. Set on a node parse returned; a child node holds none.

Returns

The expression's JSON.

Definition at line 287 of file rules.hpp.

operands()

std::span< std::string const > morph::forms::RuleExpr::operands ( ) const

inlinenodiscardnoexcept

The wire names the translation reads, by operand index (f0 is the first).

Returns

The operands.

Definition at line 291 of file rules.hpp.

evaluate()

Tri morph::forms::RuleExpr::evaluate ( RuleLookup const & lookup ) const

inlinenodiscard

Evaluates the translation with the UI document's evaluator.

For a gating rule this is its test; for visibleWhen, readonlyWhen and the presentation side of requiredWhen use whenHolds.

Parameters

lookup

Reads each operand.

Returns

The verdict: null is Unknown.

Definition at line 299 of file rules.hpp.

whenHolds()

Tri morph::forms::RuleExpr::whenHolds ( RuleLookup const & lookup ) const

inlinenodiscard

Evaluates the when clause of a requiredWhen, visibleWhen or readonlyWhen.

Parameters

lookup

Reads each operand.

Returns

The clause's verdict; Unknown for any other kind.

Definition at line 310 of file rules.hpp.

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The documentation for this class was generated from the following file:

• morph/forms/engine/rules.hpp