Class Hook

A Hook is a set of user-defined callbacks that are executed by the SDK at various points of interest. To create your own hook with customized logic, derive from Hook and override its methods.

Hook currently defines an "evaluation" series, which is composed of two stages: "beforeEvaluation" and "afterEvaluation".

These are executed by the SDK before and after the evaluation of a feature flag.

Multiple hooks may be configured in the SDK. By default, the SDK will execute each hook's beforeEvaluation stage in the order they were configured, and afterEvaluation in reverse order.

This means the last hook defined will tightly wrap the evaluation process, while hooks defined earlier in the sequence are nested outside of it.

Inheritance

object

Hook

Implements

IDisposable

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: LaunchDarkly.Sdk.Server.Hooks

Assembly: LaunchDarkly.ServerSdk.dll

Syntax

public class Hook : IDisposable

Constructors

Hook(string)

Constructs a new Hook with the given name. The name may be used in log messages.

Declaration

public Hook(string name)

Parameters

Type	Name	Description
string	name	the name of the hook

Properties

Metadata

Access this hook's HookMetadata.

Declaration

public HookMetadata Metadata { get; }

Property Value

Type	Description
HookMetadata

Methods

AfterEvaluation(EvaluationSeriesContext, ImmutableDictionary<string, object>, EvaluationDetail<LdValue>)

AfterEvaluation is executed by the SDK after the evaluation of a feature flag. It does not apply to evaluations performed during a call to AllFlagsState.

The function should return the given ImmutableDictionary<TKey, TValue> unmodified, for forward compatibility with subsequent stages that may be added.

Declaration

public virtual ImmutableDictionary<string, object> AfterEvaluation(EvaluationSeriesContext context, ImmutableDictionary<string, object> data, EvaluationDetail<LdValue> detail)

Parameters

Type	Name	Description
EvaluationSeriesContext	context	parameters associated with this evaluation
ImmutableDictionary<string, object>	data	user-configurable data from the BeforeEvaluation(EvaluationSeriesContext, ImmutableDictionary<string, object>) stage
EvaluationDetail<LdValue>	detail	flag evaluation result

Returns

Type	Description
ImmutableDictionary<string, object>	user-configurable data, which is currently unused but may be forwarded to subsequent stages in future versions of the SDK

BeforeEvaluation(EvaluationSeriesContext, ImmutableDictionary<string, object>)

BeforeEvaluation is executed by the SDK before the evaluation of a feature flag. It does not apply to evaluations performed during a call to AllFlagsState.

To pass user-configured data to AfterEvaluation(EvaluationSeriesContext, ImmutableDictionary<string, object>, EvaluationDetail<LdValue>), return a modification of the given ImmutableDictionary<TKey, TValue>. You may use existing ImmutableDictionary methods, for example:

var builder = data.ToBuilder();
builder["foo"] = "bar";
return builder.ToImmutable();

Or, you may use the SeriesDataBuilder for a fluent API:

return new SeriesDataBuilder(data).Set("foo", "bar").Build();

The modified data is not shared with any other hook. It will be passed to subsequent stages in the evaluation series, including AfterEvaluation(EvaluationSeriesContext, ImmutableDictionary<string, object>, EvaluationDetail<LdValue>).

Declaration

public virtual ImmutableDictionary<string, object> BeforeEvaluation(EvaluationSeriesContext context, ImmutableDictionary<string, object> data)

Parameters

Type	Name	Description
EvaluationSeriesContext	context	parameters associated with this evaluation
ImmutableDictionary<string, object>	data	user-configurable data, currently empty

Returns

Type	Description
ImmutableDictionary<string, object>	user-configurable data, which will be forwarded to AfterEvaluation(EvaluationSeriesContext, ImmutableDictionary<string, object>, EvaluationDetail<LdValue>)

Dispose()

Disposes the hook. This method will be called when the SDK is disposed.

Declaration

public void Dispose()

Dispose(bool)

Disposes the hook. This method will be called when the SDK is disposed.

Declaration

protected virtual void Dispose(bool disposing)

Parameters

Type	Name	Description
bool	disposing	true if the caller is Dispose, false if the caller is a finalizer

Implements

IDisposable