ff4k-core/com.yonatankarp.ff4k.core/Feature

Feature

@Serializable

data class Feature(val uid: String, val isEnabled: Boolean = false, val description: String? = null, val group: String? = null, val permissions: Set<String> = emptySet(), val flippingStrategy: FlippingStrategy? = null, val customProperties: Map<String, Property<*>> = emptyMap())(source)

Represents a feature flag (feature toggle) identified by a unique identifier.

Feature flags enable/disable functionality at runtime, supporting continuous delivery and controlled feature rollouts as introduced by Martin Fowler.

Core Capabilities

Runtime Control: Enable or disable features without code changes or redeployment
Security Management: Limit feature access to specific user roles/permissions
Grouping: Organize features into groups for bulk operations
Advanced Strategies: Use FlippingStrategy for A/B testing, gradual rollouts, etc.
Custom Properties: Attach metadata and configuration to features

Immutability

This class is immutable by design. All state-changing operations (enable, disable, toggle, addProperty) return a new Feature instance rather than modifying the current one.

Example usage:

val feature = Feature(
    uid = "new-checkout-flow",
    isEnabled = true,
    description = "New streamlined checkout process",
    group = "checkout",
    permissions = setOf("BETA_TESTERS", "ADMIN")
)

// State changes return new instances
val disabled = feature.disable()
val toggled = feature.toggle()

// Add custom properties
val withProperty = feature.addProperty(
    intProperty("maxRetries") {
    value = 3
  }
)

Throws

IllegalArgumentException

if uid is blank or group is blank (when non-null)

Constructors

constructor(uid: String, isEnabled: Boolean = false, description: String? = null, group: String? = null, permissions: Set<String> = emptySet(), flippingStrategy: FlippingStrategy? = null, customProperties: Map<String, Property<*>> = emptyMap())

Properties

customProperties

val customProperties: Map<String, Property<*>>

Custom properties attached to this feature.

val description: String?

Optional human-readable description of this feature.

displayStrategyClassName

val displayStrategyClassName: String?

The simple class name of the flippingStrategy, or null if no strategy is set.

flippingStrategy

val flippingStrategy: FlippingStrategy?

Optional strategy for advanced feature activation logic.

val group: String?

Optional group name for organizing related features.

hasFlippingStrategy

val Feature.hasFlippingStrategy: Boolean

Checks if this feature has a flipping strategy configured.

val Feature.hasPermissions: Boolean

Checks if this feature has any permission restrictions.

val Feature.isDisabled: Boolean

Checks if this feature is disabled.

val isEnabled: Boolean

Whether this feature is currently enabled.

val permissions: Set<String>

Set of roles or permissions required to access this feature.

val Feature.propertyNames: Set<String>

Returns the set of all custom property names attached to this feature.

val uid: String

Unique identifier for this feature.

Functions

fun Feature.addGroup(groupName: String): Feature

Returns a new Feature associated with the specified group.

fun Feature.addProperties(vararg properties: Property<*>): Feature

fun Feature.addProperties(properties: Collection<Property<*>>): Feature

Returns a new Feature with multiple properties added.

fun addProperty(property: Property<*>): Feature

Returns a new Feature instance with the given property added to customProperties.

clearPermissions

fun Feature.clearPermissions(): Feature

Returns a new Feature with all permissions removed.

clearProperties

fun Feature.clearProperties(): Feature

Returns a new Feature with all custom properties removed.

fun disable(): Feature

Returns a new Feature instance with isEnabled set to false.

fun enable(): Feature

Returns a new Feature instance with isEnabled set to true.

getPropertiesOfType

inline fun <T> Feature.getPropertiesOfType(): Map<String, Property<T>>

Returns all custom properties whose values are of the specified type.

fun <T> getProperty(propertyId: String): Property<T>?

Retrieves a custom property by name.

getPropertyOrThrow

inline fun <T> Feature.getPropertyOrThrow(name: String): Property<T>

Retrieves a custom property by name, throwing an exception if not found.

getPropertyValueOrDefault

inline fun <T> Feature.getPropertyValueOrDefault(name: String, default: T): T

Retrieves a custom property's value by name, returning a default if not found.

grantPermissions

fun Feature.grantPermissions(vararg permissions: String): Feature

fun Feature.grantPermissions(permissions: Collection<String>): Feature

Returns a new Feature with the specified permissions granted.

hasAllPermissions

fun Feature.hasAllPermissions(vararg permissions: String): Boolean

Checks if this feature has all of the specified permissions.

hasAnyPermission

fun Feature.hasAnyPermission(vararg permissions: String): Boolean

Checks if this feature has at least one of the specified permissions.

hasPropertyWithValue

fun <T> Feature.hasPropertyWithValue(name: String, value: T): Boolean

Checks if a property exists and has a specific value.

fun Feature.removeGroup(): Feature

Returns a new Feature removed from its current group.

removeProperties

fun Feature.removeProperties(vararg names: String): Feature

fun Feature.removeProperties(names: Collection<String>): Feature

Returns a new Feature with the specified properties removed.

revokePermissions

fun Feature.revokePermissions(vararg permissions: String): Feature

fun Feature.revokePermissions(permissions: Collection<String>): Feature

Returns a new Feature with the specified permissions revoked.

fun toggle(): Feature

Returns a new Feature instance with isEnabled toggled.