ConditionalOnClass class

An annotation that conditionally activates a Component, Pod, or configuration class only if specific classes are present in the Dart runtime or compilation environment.

The ConditionalOnClass annotation allows JetLeaf to selectively load components based on the presence of other classes, enabling modular configuration and safe integration with optional dependencies.

Purpose

In JetLeaf applications, some modules or configurations should only initialize when certain external or framework classes are available. This is especially useful for optional integrations, third-party dependencies, or feature toggles controlled by class availability.

ConditionalOnClass provides a declarative, type-safe mechanism for expressing such conditions without resorting to procedural runtime checks or try-catch imports.

Behavior

• values may include:

  • A Dart Type (e.g., MyService)
  • A ClassType wrapper (e.g., ClassType<MyService>())
  • A qualified class name string (e.g., 'package:app/core/logger.dart.LoggingService')

• The annotated element is processed only if all specified classes exist.

• If any referenced class cannot be resolved, the condition fails silently, and the annotated element is skipped.

Example

// Activated only if AdvancedCache class is available
@ConditionalOnClass([ClassType<AdvancedCache>()])
class AdvancedCacheConfig {}

// Activated only if LoggingService class exists by qualified name
@ConditionalOnClass([
  ClassType.qualified('package:jetleaf/example/jetleaf_example.dart.LoggingService')
])
class LoggingConfig {}

Related Components

• ConditionalContext – Evaluates and manages class- and pod-based conditional activation.
• Conditional – The core conditional annotation base class that this extends.
• ConditionalOnMissingClass – The inverse condition, which activates only when classes are absent.

Inheritance

• Object
• WhenConditional
• ConditionalOnClass

Annotations

• @Conditional([OnClassCondition()])
• @Target.new({TargetKind.classType, TargetKind.method})

Constructors

ConditionalOnClass([List<Object> values = const []])

An annotation that conditionally activates a Component, Pod, or configuration class only if specific classes are present in the Dart runtime or compilation environment.

const

Properties

annotationType → Type

Returns the annotation _type of this annotation.

no setter

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

values → List<Object>

The list of class identifiers that must be present for activation.

final

Methods

equalizedProperties() → List<Object?>

Mixin-style contract for value-based equality, hashCode, and toString.

equals(Object other) → bool

Checks whether the given object is logically equivalent to this annotation.

inherited

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

Returns a string representation of this annotation.

Operators

operator ==(Object other) → bool

The equality operator.

inherited