self-assert / Rule

Class: abstract Rule<PredicateReturnType, ValueType>

Represents a validation rule in the problem domain.

This is the base class for all rules.

• Use Assertion for rules that can be evaluated synchronously.
• Use Inquiry for rules that need to be evaluated asynchronously.

Rules are identified by a unique identifier (labelId) and a human-readable description. These identifiers are meant to be meaningful within the domain, and can be used to route or display validation errors.

Extended by

• Assertion
• Inquiry

Type Parameters

Type Parameter	Default type	Description
PredicateReturnType extends MaybeAsync<boolean>	-	The return type of the predicate functions. Specifically, true or Promise<true>.
ValueType	any	The type of value this rule applies to.

Implements

• LabeledRule

Rule definition

Related to the definition of requirements for business rules.

require()

require(aConditionToBeMet): this

Adds a necessary requirement for the rule to hold.

Parameters

Parameter	Type
aConditionToBeMet	RuleRequirement<PredicateReturnType, ValueType>

Returns

this

this for chaining

Example

Add a requirement for the rule to hold

const nameValid = Assertion.requiring(
  "customer.name.notBlank",
  "Name must not be blank",
  Requirements.isNotBlank
);
nameValid.require((name) => name !== "Johnny");

console.log(nameValid.hasFailed("")); // true
console.log(nameValid.hasFailed("Johnny")); // true
console.log(nameValid.doesHold("John")); // true

Rule evaluation

Related to the definition of business rules and their evaluation.

doesHold()

abstract doesHold(value): PredicateReturnType

Evaluates the requirements for the given value, and returns whether the rule holds or not.

Parameters

Parameter	Type
value	ValueType

Returns

PredicateReturnType

---

hasFailed()

abstract hasFailed(value): PredicateReturnType

Opposite of doesHold

Parameters

Parameter	Type
value	ValueType

Returns

PredicateReturnType

---

mustHold()

abstract mustHold(value): PredicateReturnType extends boolean ? void : Promise<void>

Evaluates the requirements for the given value. If any condition is not met, throws a RulesBroken exception.

Parameters

Parameter	Type
value	ValueType

Returns

PredicateReturnType extends boolean ? void : Promise<void>

---

collectFailureInto()

abstract collectFailureInto(failed, value): PredicateReturnType extends boolean ? void : Promise<void>

Updates the list of failed assertions with its label if the rule has failed for the given value.

Parameters

Parameter	Type
failed	LabeledRule[]
value	ValueType

Returns

PredicateReturnType extends boolean ? void : Promise<void>

---

evaluateFor()

evaluateFor(aValue): RuleEvaluation<PredicateReturnType, ValueType>

Prepares a RuleEvaluation for the given value.

This is the same as new RuleEvaluation(rule, value).

Parameters

Parameter	Type
aValue	ValueType

Returns

RuleEvaluation<PredicateReturnType, ValueType>

Example

const nameNotBlank = Assertion.requiring(
  "customer.name.notBlank",
  "Name must not be blank",
  Requirements.isNotBlank
);

const evaluation = nameNotBlank.evaluateFor("John");
console.log(evaluation.doesHold()); // true

Labeling

isLabeledAs()

isLabeledAs(aBrokenRuleLabel): boolean

Checks if the assertion has the same id and description as the given one.

Parameters

Parameter	Type
aBrokenRuleLabel	LabeledRule

Returns

boolean

Implementation of

LabeledRule.isLabeledAs

---

hasLabel()

hasLabel(anId, aDescription): boolean

Compare the id and description of the assertion with the given ones.

Parameters

Parameter	Type
anId	string
aDescription	string

Returns

boolean

Implementation of

LabeledRule.hasLabel

---

hasDescription()

hasDescription(aDescription): boolean

Checks if the assertion has the given description.

Parameters

Parameter	Type
aDescription	string

Returns

boolean

Remarks

This method is used mostly for testing.

Implementation of

LabeledRule.hasDescription

---

hasLabelId()

hasLabelId(anId): boolean

Compares the id of the assertion with the given one.

Parameters

Parameter	Type
anId	string

Returns

boolean

Implementation of

LabeledRule.hasLabelId

---

getId()

getId(): string

Returns the label identifier.

Returns

string

Implementation of

LabeledRule.getId

---

getDescription()

getDescription(): string

Returns

string

Implementation of

LabeledRule.getDescription