spotify/confidence-sdk-swift

Swift Confidence SDK

This repo contains the official Swift SDK 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 website.

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 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: "0.3.0")

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 (only recommended if you are making changes to the SDK)
   • Clone locally using your preferred method
   • Use the "Add Local..." button to select the local folder

Swift 6 support

If your app is using some of the features of Swift 6, we recommend setting the Strict Concurrency Checking to Minimal.

Creating the Confidence instance

import Confidence

let confidence = Confidence.Builder(clientSecret: "mysecret", loggerLevel: .NONE).build()
await confidence.fetchAndActivate()

• The clientSecret for your application can be generated in the Confidence portal.
• The loggerLevel sets the verbosity level for logging to console. This can be useful while testing your integration with the Confidence SDK.

Note: the Confidence SDK has been intended to work as a single instance in your Application. Creating multiple instances in the same runtime could lead to unexpected behaviours.

Initialization strategy

confidence.activateAndFetch() is an async function that fetches the flags from the Confidence backend, stores the result on disk, and make the same data ready for the Application to be consumed.

The alternative option is to call confidence.activate(): this loads previously fetched flags data from storage and makes that available for the Application to consume right away. To avoid waiting on backend calls when the Application starts, the suggested approach is to call confidence.activate() and then trigger a background refresh via confidence.asyncFetch() for future sessions.

Setting the context

The context is a key-value map used for sampling and for targeting, when flag are evaluated by the Confidence backend. It is also appended to the tracked events, making it a great way to create dimensions for metrics in Confidence.

confidence.putContext(context: ["key": ConfidenceValue(string: "value")])

Note that a ConfidenceValue is accepted a map values, which has a constructor for all the value types supported by Confidence.

Resolving feature flags

Once the Confidence instance is activated, you can access the flag values using the getValue method or the getEvaluation functions. Both functions use 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> = 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:

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

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

Note that the data struct can't contain the key context, as that is reserved for entries set via putContext (see below): violating this rule will cause the track function to throw an error.

To set context data to be appended to all tracked events, here is an example:

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

OpenFeature Provider

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