C/C++ SDK reference (client-side)

Overview

This topic documents how to get started with the client-side C/C++ SDK, and links to reference information on all of the supported features.

Prerequisites

To use the C/C++ SDK, you must have the following prerequisites:

• Windows or a POSIX environment (Linux, OSX, BSD)
• The networking library libcurl
• libpthread, if you are using a POSIX environment

Configuring the SDK

The following sections explain how to install and configure the SDK, and then to verify its connection to LaunchDarkly by fetching flag configuration information for a specific user.

Installing the SDK

Here's how to install the SDK:

1. Clone the GitHub repository or download a release archive from the GitHub Releases page.
2. Install the SDK locally.

• If you use cmake, the build system will expect that libcurl, and libpthread if you are on POSIX, exist on the system. The cmake configuration exports the target ldclientapi.
• If you don't use cmake and you cannot use LaunchDarkly's artifacts, use cmake install to install the SDK in directory you choose. This copies the required headers, and binaries equivalent to LaunchDarkly's release bundles.

3. Build the C++ wrapper, which is not included in the release binaries. Copy the header and source files and add them to your own build system.
4. Include the LaunchDarkly SDK headers:

#include <launchdarkly/api.h>
COPY

5. Create a single shared instance of LDClient.
6. Specify your mobile key to authorize your application to connect to a particular environment within LaunchDarkly:

unsigned int maxwaitmilliseconds = 10 * 1000;
struct LDConfig *config = LDConfigNew("mobile-key-123abc");
struct LDUser *user = LDUserNew("user-key-123abc");
struct LDClient *client = LDClientInit(config, user, maxwaitmilliseconds);
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Your environment's mobile key is available in the Projects tab of your account settings page.

Fetching flag configuration

Here's how to verify the SDK is configured correctly by fetching flag configuration data from LaunchDarkly:

1. Call LDClientInit to initiate a remote call to the LaunchDarkly service. This fetches the feature flag settings for a given user.

   This call blocks up to the time defined by maxwaitmilliseconds. If you request a feature flag before initialization completes, you will receive the default flag value. If you want to wait for client initialization, register a callback:

void initCallback(LDStatus status)
{
    if (status == LDStatusInitialized) {
        printf("Completed LaunchDarkly client initialization");
    }
}
LDSetClientStatusCallback(initCallback);
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2. Use client to check which variation a specific user should receive for a certain feature flag:

bool show_feature = LDBoolVariation(client, "flag-key-123abc", false);
if (show_feature) {
    // Application code to show the feature
} else {
    // The code to run if the feature is off
}
COPY

Shutting down

Shut down the client when your application terminates. To learn more, read Shutting down.

Supported features

This SDK supports the following features:

• Aliasing users
• Anonymous contexts and users
• Configuration
• Evaluating flags
• Flushing events
• Identifying and changing contexts
• Private attributes
• Sending custom events
• Service endpoint configuration
• Shutting down
• User and context configuration
• Web proxy configuration