Okyline Core Quick Reference - Conditional Directives

Version: 1.7.0 Date: May 2026 Status: Draft

Companion to the Okyline Core Quick Reference - Basis. Covers conditional directives that gate required / forbidden / applied field rules on the value or presence of other fields.

Conditional Directives

Directive	Value	Effect
`$requiredIf field(cond)`	`[fields]`	Listed fields required when condition on field is true
`$requiredIfNot field(cond)`	`[fields]`	Listed fields required when condition on field is false
`$requiredIfExist field`	`[fields]`	Listed fields required when field exists
`$requiredIfNotExist field`	`[fields]`	Listed fields required when field is absent
`$forbiddenIf field(cond)`	`[fields]`	Listed fields forbidden when condition on field is true
`$forbiddenIfNot field(cond)`	`[fields]`	Listed fields forbidden when condition on field is false
`$forbiddenIfExist field`	`[fields]`	Listed fields forbidden when field exists
`$forbiddenIfNotExist field`	`[fields]`	Listed fields forbidden when field is absent
`$appliedIf field(cond)`	`{...}`	Structure applied when condition on field is true
`$appliedIfExist field`	`{...}`	Structure applied when field exists
`$appliedIfNotExist field`	`{...}`	Structure applied when field is absent
`$required`	`[fields]`	Unconditional required fields
`$forbidden`	`[fields]`	Unconditional forbidden fields
`$atLeastOne`	`[fields]`	At least one field from group must be present
`$mutuallyExclusive`	`[fields]`	At most one field from group may be present
`$exactlyOne`	`[fields]`	Exactly one field from group must be present
`$allOrNone`	`[fields]`	All fields in group present, or none

Condition syntax: field(values) or field(min..max) or field(_TypeGuard_) or field(null)

Suffix mechanism: To declare multiple independent groups of the same directive in one object, append a unique suffix: $atLeastOne_contact, $atLeastOne_address, etc. The suffix is semantically ignored.

Examples:

"$requiredIf age(<18)": ["parentConsent"]

↳ parentConsent required when age is less than 18

"$forbiddenIf status('CLOSED')": ["lastLogin"]

↳ lastLogin forbidden when status equals “CLOSED”

"$requiredIfExist shipping": ["shippingAddress"]

↳ shippingAddress required when shipping field exists

"$appliedIf status('ACTIVE')": {
  "workDays|@ (1..22)": 20
}

↳ workDays field added to schema when status equals “ACTIVE”

Switch form:

"$appliedIf paymentMethod": {
  "('CARD')": { "cardNumber|@ {16}": "1234..." },
  "('PAYPAL')": { "email|@ ~$Email~": "a@b.c" },
  "$else": { "reference|@": "REF-001" }
}

↳ Different fields required depending on paymentMethod value

Inside an $appliedIf* block (incl. $else / $notExist / switch cases) you can use any directive above - except another $appliedIf* (no nesting) and $field. They check the surrounding object and apply only while the branch is active.

Unconditional directives:

"$required": ["firstName", "lastName"],
"$forbidden": ["internalCode"],
"$exactlyOne": ["email", "phone"],
"$allOrNone": ["street", "city", "zip"]

Null literal in conditions:

"$requiredIf status('CANCELLED', null)": ["reason"]

↳ reason required when status is "CANCELLED" or null

Path Expressions in conditions: conditions can target this., parent., or root. paths - see the Basis Quick Reference for prefix rules and type guards.

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