Swift Confidence SDK

This repo contains the Swift Confidence SDK to be used for accessing feature flags and for event tracking with Confidence.

It also contains the Confidence OpenFeature Provider, to be used in conjunction with the OpenFeature SDK.

For documentation related to flags management and event tracking in Confidence, refer to the Confidence documentation portal.

Functionalities:

• Managed integration with the Confidence backend
• Prefetch and cache flag evaluations, for fast value reads even when the application is offline
• Automatic data collection (in the backend) about which flags have been accessed by the application
• Event tracking for instrumenting your application

Dependency Setup

Swift Package Manager

In the dependencies section of Package.swift add:

.package(url: "git@github.com:spotify/confidence-sdk-swift.git", from: "0.2.0")

and in the target dependencies section add:

.product(name: "Confidence", package: "confidence-sdk-swift"),

Xcode Dependencies

You have two options, both start from File > Add Packages... in the code menu.

First, ensure you have your GitHub account added as an option (+ > Add Source Control Account...). You will need to create a Personal Access Token with the permissions defined in the Xcode interface.

1. Add as a remote repository
   • Search for git@github.com:spotify/confidence-sdk-swift.git and click "Add Package"
2. Clone the repository locally
   • Clone locally using your preferred method
   • Use the "Add Local..." button to select the local folder

Note: Option 2 is only recommended if you are making changes to the provider, you will also need to add the relevant OpenFeature SDK dependency manually.

Creating the Confidence instance

You can create the Confidence instance using a Builder pattern. The client secret for your application is obtained in the Confidence portal link.

Make the initial fetching of flags using the activateAndFetch method. This is an async function that will fetch the flags from the server and activate them. It needs to be run with await.

import Confidence

let confidence = Confidence.Builder(clientSecret: "mysecret").build()
await confidence.fetchAndActivate()

Setting the context

The context is a key-value map that will be used for sampling and for targeting input in assigning feature flag values by the Confidence backend. It is also a crucial way to create dimensions for metrics generated by event data.

The Confidence SDK supports multiple ways to set the Context. Some of them are mutating the current context of the Confidence instance, others are returning a new instance with the context changes applied.

confidence.putContext(context: ["key": ConfidenceValue(string: "value")]) // this will mutate the context of the current Confidence instance

let otherConfidenceInstance = confidence.withContext(["key": ConfidenceValue(string: "value")]) // this will return a new Confidence instance with the context changes applied but the context of the original instance is kept intact

Resolving feature flags

Once the flags are fetched and activated, you can access their value using the getValue method or the getEvaluation method. Both methods uses generics to return a type defined by the default value type.

The method getEvaluation returns an Evaluation object that contains the value of the flag, the reason for the value returned, and the variant selected.

The method getValue will simply return the assigned value or the default. In the case of an error, the default value will be returned and the Evaluation contains information about the error.

let message: String = confidence.getValue(key: "flag-name.message", defaultValue: "default message") 
let messageFlag: Evaluation<String> = try confidence.getEvaluation(key: "flag-name.message", defaultValue: "default message")

let messageValue = messageFlag.value
// message and messageValue are the same

Tracking events

The Confidence instance offers APIs to track events, which are uploaded to the Confidence backend:

confidence.track(eventName: "MyEvent", message: ["field": ConfidenceValue(string("value"))])

The SDK takes care of storing events in case of offline and retries in case of transient failures.

It's also possible to set context data to be appended to all tracked events:

confidence.putContext(context: ["os_version": ConfidenceValue(string: "17.0")])

Confidence APIs allows to spawn child instances that inherit the parent's context:

let child_confidence = confidence.withContext(["new_context", ConfidenceValue(string: "new_value")])

Tracking events with child_confidence will include the context data from all its ancestors (i.e. os_version, and the evaluation context).

Note: the context in the Confidence instance used to initialize the OpenFeature Provider is also part of the Evaluation Context used for flags.

OpenFeature Provider

If you want to use OpenFeature, an OpenFeature Provider for the OpenFeature SDK is also available.

Usage

See the dedicated Provider Readme.