Objective-C Core Interfaces

The LDClient is the heart of the SDK, providing client apps running iOS, watchOS, macOS, or tvOS access to LaunchDarkly services. This singleton provides the ability to set a configuration (LDConfig) that controls how the LDClient talks to LaunchDarkly servers, and a context (LDContext) that provides finer control on the feature flag values delivered to LDClient. Once the LDClient has started, it connects to LaunchDarkly’s servers to get the feature flag values you set in the Dashboard.

Objc Classes

The SDK creates an Objective-C native style API by wrapping Swift specific classes, properties, and methods into Objective-C wrapper classes prefixed by Objc. By defining Objective-C specific names, client apps written in Objective-C can use a native coding style, including using familiar LaunchDarkly SDK names like LDClient, LDConfig, and LDContext. Objective-C developers should refer to the Objc documentation by following the Objc specific links following type, property, and method names.

Usage

Startup

1. To customize, configure a LDConfig (ObjcLDConfig) and LDContext (ObjcLDContxt). Both give you additional control over the feature flags delivered to the LDClient. See ObjcLDConfig & ObjcLDContext for more details.
2. The mobileKey set into the LDConfig comes from your LaunchDarkly Account settings (on the left, at the bottom). If you have multiple projects be sure to choose the correct Mobile key.
3. Call [ObjcLDClient startWithConfig: context: completion:] (ObjcLDClient.startWithConfig(_:config:context:completion:))
4. If you do not pass in a LDContext, LDCLient will create a default for you.
5. The optional completion closure allows the LDClient to notify your app when it has gone online.
6. Because the LDClient is a singleton, you do not have to keep a reference to it in your code.

Getting Feature Flags

Once the LDClient has started, it makes your feature flags available using the variation and variationDetail methods. A variation is a specific flag value. For example, a boolean feature flag has 2 variations, YES and NO. You can create feature flags with more than 2 variations using other feature flag types. See LDValue for the available types.

BOOL boolFlag = [ldClientInstance boolVariationForKey:@"my-bool-flag" defaultValue:NO];

If you need to know more information about why a given value is returned, the typed variationDetail methods return an LD<T>EvaluationDetail with an detail about the evaluation.

LDBoolEvaluationDetail *boolVariationDetail = [ldClientInstance boolVariationDetail:@"my-bool-flag" defaultValue:NO];
BOOL boolFlagValue = boolVariationDetail.value;
NSInteger boolFlagVariation = boolVariationDetail.variationIndex
NSDictionary boolFlagReason = boolVariationValue.reason;

See the typed -[LDCLient variationForKey: defaultValue:] or -[LDClient variationDetailForKey: defaultValue:] methods in the section Feature Flag values for details.

Observing Feature Flags

If you want to know when a feature flag value changes, you can check the flag’s value. You can also use one of several observe methods to have the LDClient notify you when a change occurs. There are several options– you can setup notifications based on when a specific flag changes, when any flag in a collection changes, or when a flag doesn’t change. The flag change listener may be invoked multiple times per invocation of LDClient.identify as the SDK fetches up to date flag data from multiple sources (e.g. local cache, cloud services). In certain error cases, the SDK may not be able to retrieve flag data during an identify (e.g. no network connectivity). In those cases, the flag change listener may not be invoked.

__weak typeof(self) weakSelf = self;
[ldClientInstance observeBool:@"my-bool-flag" owner:self handler:^(LDBoolChangedFlag *changedFlag) {
   __strong typeof(weakSelf) strongSelf = weakSelf;
   [strongSelf updateFlagWithKey:@"my-bool-flag" changedFlag:changedFlag];
}];

The changedFlag passed in to the block contains the old and new value. See the typed LDChangedFlag classes in the Obj-C Changed Flags.

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@objc(LDClient)
public final class ObjcLDClient : NSObject

Use LDConfig to configure the LDClient. When initialized, a LDConfig contains the default values which can be changed as needed.

The client app can change the LDConfig by getting the config from LDClient (ObjcLDClient), adjusting the values, and setting it back into the LDClient (ObjcLDClient).

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@objc(LDConfig)
public final class ObjcLDConfig : NSObject

Undocumented

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@objc(Reference)
public final class ObjcLDReference : NSObject

LDContext is a collection of attributes that can be referenced in flag evaluations and analytics events.

To create an LDContext of a single kind, such as a user, you may use LDContextBuilder.

To create an LDContext with multiple kinds, use LDMultiContextBuilder.

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@objc(LDContext)
public final class ObjcLDContext : NSObject

Collects the elements of a feature flag that changed as a result of a clientstream update or feature flag request. The SDK will pass a typed ObjcLDChangedFlag or a collection of ObjcLDChangedFlags into feature flag observer blocks. This is the base type for the typed ObjcLDChangedFlags passed into observer blocks. The client app will have to convert the ObjcLDChangedFlag into the expected typed ObjcLDChangedFlag type.

See the typed ObjcLDClient observeWithKey:owner:handler:, observeWithKeys:owner:handler:, and observeAllWithOwner:handler: for more details.

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@objc(LDChangedFlag)
public class ObjcLDChangedFlag : NSObject

Bridged LDValue type for Objective-C.

Can create instances from Objective-C with the provided of static functions, for example [LDValue ofBool:YES].

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@objc(LDValue)
public final class ObjcLDValue : NSObject

Used to represent the type of an LDValue.

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@objc(LDValueType)
public enum ObjcLDValueType : Int