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iOS (Swift) SDK Reference

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ConfigCat Swift SDK on GitHub

Getting Started:

1. Add the ConfigCat SDK to your project

CocoaPods

target '<YOUR TARGET>' do
pod 'ConfigCat'
end

Then, run the following command to install your dependencies:

pod install

Carthage

github "configcat/swift-sdk"

Then, run the carthage update command and then follow the Carthage integration steps to link the framework with your project.

Swift Package Manager

Add the SDK to your Package.swift.

dependencies: [
.package(
url: "https://github.com/configcat/swift-sdk",
from: "9.0.1"
)
]

2. Import the ConfigCat SDK:

import ConfigCat

3. Create the ConfigCat client with your SDK Key

let client = ConfigCatClient(sdkKey: "<PLACE-YOUR-SDK-KEY-HERE>")

4. Get your setting value

client.getValue(for: "isMyAwesomeFeatureEnabled", defaultValue: false) { isMyAwesomeFeatureEnabled in
if isMyAwesomeFeatureEnabled {
doTheNewThing()
} else {
doTheOldThing()
}
}

// Or with async/await
let isMyAwesomeFeatureEnabled = await client.getValue(for: "isMyAwesomeFeatureEnabled", defaultValue: false)
if isMyAwesomeFeatureEnabled {
doTheNewThing()
} else {
doTheOldThing()
}

Creating the ConfigCat Client

ConfigCat Client is responsible for:

  • managing the communication between your application and ConfigCat servers.
  • caching your setting values and feature flags.
  • serving values quickly in a failsafe way.

ConfigCatClient(sdkKey: <sdkKey>) returns a client with default options.

ArgumentsTypeDescription
sdkKeyStringREQUIRED. SDK Key to access your feature flags and configurations. Get it from ConfigCat Dashboard.
dataGovernanceDataGovernanceOptional, defaults to global. Describes the location of your feature flag and setting data within the ConfigCat CDN. This parameter needs to be in sync with your Data Governance preferences. More about Data Governance. Available options: global, euOnly.
configCacheConfigCache?Optional, sets a custom cache implementation for the client. See below.
refreshModePollingMode?Optional, sets the polling mode for the client. See below.
sessionConfigurationURLSessionConfigurationOptional, sets a custom URLSessionConfiguration used by the HTTP calls.
baseUrlStringObsolete Optional, sets the CDN base url (forward proxy, dedicated subscription) from where the sdk will download the configurations.
flagOverridesOverrideDataSource?Optional, configures local feature flag & setting overrides. More about feature flag overrides.
logLevelLogLevelOptional, sets the internal log level. See below.
caution

We strongly recommend you to use the ConfigCatClient as a Singleton object in your application. If you want to use multiple SDK Keys in the same application, create only one ConfigCatClient per SDK Key.

Anatomy of getValue()

ParametersDescription
keyREQUIRED. Setting-specific key. Set on ConfigCat Dashboard for each setting.
defaultValueREQUIRED. This value will be returned in case of an error.
userOptional, User Object. Essential when using Targeting. Read more about Targeting.
completionREQUIRED. Callback function to call, when the result is ready.
client.getValue(
for: "keyOfMySetting", // Setting Key
defaultValue: false, // Default value
user: ConfigCatUser(identifier: "435170f4-8a8b-4b67-a723-505ac7cdea92") // Optional User Object
) { isMyAwesomeFeatureEnabled in
if isMyAwesomeFeatureEnabled {
doTheNewThing()
} else {
doTheOldThing()
}
}

Anatomy of asynchronous getValue()

ParametersDescription
keyREQUIRED. Setting-specific key. Set on ConfigCat Dashboard for each setting.
defaultValueREQUIRED. This value will be returned in case of an error.
userOptional, User Object. Essential when using Targeting. Read more about Targeting.
let value = await client.getValue(
for: "keyOfMySetting", // Setting Key
defaultValue: false, // Default value
user: ConfigCatUser(identifier: "435170f4-8a8b-4b67-a723-505ac7cdea92") // Optional User Object
)

User Object

The User Object is essential if you'd like to use ConfigCat's Targeting feature.

let user = ConfigCatUser(identifier: "435170f4-8a8b-4b67-a723-505ac7cdea92")   
let user = ConfigCatUser(identifier: "[email protected]")   
ArgumentsDescription
identifierREQUIRED. Unique identifier of a user in your application. Can be any value, even an email address.
emailOptional parameter for easier targeting rule definitions.
countryOptional parameter for easier targeting rule definitions.
customOptional dictionary for custom attributes of a user for advanced targeting rule definitions. e.g. User role, Subscription type.
let user = ConfigCatUser(identifier: "435170f4-8a8b-4b67-a723-505ac7cdea92",
email: "[email protected]",
country: "United Kingdom",
custom: ["SubscriptionType":"Pro", "UserRole":"Admin"])

Logging

We are using the Unified Logging System in the ConfigCat SDK for logging. For more information about Unified Logging please visit

Apple's developer pageor check Session 721 - Unified Logging and Activity Tracing from WWDC 2016.

Log level

You can change the verbosity of the logs by passing a logLevel parameter to the ConfigCatClient's init function.

let client = ConfigCatClient(sdkKey: "<PLACE-YOUR-SDK-KEY-HERE>", logLevel: .info)

Available log levels:

LevelDescription
.nologTurn the ConfigCat logging off.
.errorOnly error level events are logged.
.warningDefault. Errors and Warnings are logged.
.infoErrors, Warnings and feature flag evaluation is logged.
.debugAll of the above plus debug info is logged. Debug logs can be different for other SDKs.

Info level logging helps to inspect the feature flag evaluation process.
Example log entries:

[main] Evaluating getValue(isPOCFeatureEnabled).
User object: {
"Identifier" : "435170f4-8a8b-4b67-a723-505ac7cdea92",
"Email" : "[email protected]"
}.
Evaluating rule: [Email:[email protected]] [CONTAINS] [@something.com] => no match
Evaluating rule: [Email:[email protected]] [CONTAINS] [@example.com] => match, returning: Optional(true)

getAllKeys()

You can get all the setting keys from your configuration by calling the getAllKeys() method of the ConfigCatClient.

let client = ConfigCatClient(sdkKey: "<PLACE-YOUR-SDK-KEY-HERE>")

// Completion callback
client.getAllKeys() { keys in
// use keys
}

// Async/await
let keys = await client.getAllKeys()

getAllValues()

Evaluates and returns the values of all feature flags and settings. Passing a User Object is optional.

ParametersDescription
userOptional, User Object. Essential when using Targeting. Read more about Targeting.
let client = ConfigCatClient(sdkKey: "<PLACE-YOUR-SDK-KEY-HERE>")

// Completion callback
client.getAllValues(
user: ConfigCatUser(identifier: "435170f4-8a8b-4b67-a723-505ac7cdea92") // Optional User Object
) { allValues in
// use allValues
}

// Async/await
let allValues = await client.getAllValues(
user: ConfigCatUser(identifier: "435170f4-8a8b-4b67-a723-505ac7cdea92") // Optional User Object
)

Polling Modes

The ConfigCat SDK supports 3 different polling mechanisms to acquire the setting values from ConfigCat. After latest setting values are downloaded, they are stored in the internal cache then all getValue() calls are served from there. With the following polling modes, you can customize the SDK to best fit to your application's lifecycle.
More about polling modes.

Auto polling (default)

The ConfigCat SDK downloads the latest values and stores them automatically every 60 seconds.

Use the the autoPollIntervalInSeconds option parameter of the PollingModes.autoPoll() to change the polling interval.

let client = ConfigCatClient(
sdkKey: "<PLACE-YOUR-SDK-KEY-HERE>",
refreshMode: PollingModes.autoPoll(autoPollIntervalInSeconds: 120 /* polling interval in seconds */)
)

Adding a callback to onConfigChanged option parameter will get you notified about changes.

let client = ConfigCatClient(
sdkKey: "<PLACE-YOUR-SDK-KEY-HERE>",
refreshMode: PollingModes.autoPoll(
autoPollIntervalInSeconds: 120, // polling interval in seconds
onConfigChanged: {
// here you can subscribe to configuration changes
}
)
)

Available options:

Option ParameterDescriptionDefault
autoPollIntervalInSecondsPolling interval.60
onConfigChangedCallback to get notified about changes.-
maxInitWaitTimeInSecondsMaximum waiting time between the client initialization and the first config acquisition in secconds.5

Lazy loading

When calling getValue() the ConfigCat SDK downloads the latest setting values if they are not present or expired in the cache. In this case the getValue() will return the setting value after the cache is updated.

Use the cacheRefreshIntervalInSeconds option parameter of the PollingModes.lazyLoad() to set cache lifetime.

let client = ConfigCatClient(
sdkKey: "<PLACE-YOUR-SDK-KEY-HERE>",
refreshMode: PollingModes.lazyLoad(cacheRefreshIntervalInSeconds: 120 /* the cache will expire in 120 seconds */)
)

Available options:

Option ParameterDescriptionDefault
cacheRefreshIntervalInSecondsCache TTL.60

Manual polling

Manual polling gives you full control over when the config.json (with the setting values) is downloaded. ConfigCat SDK will not update them automatically. Calling refresh() is your application's responsibility.

let client = ConfigCatClient(
sdkKey: "<PLACE-YOUR-SDK-KEY-HERE>",
refreshMode: PollingModes.manualPoll()
)

// Completion callback
client.refresh() {
// The client uses the latest configuration
}

// Async/await
await client.refresh()

getValue() returns defaultValue if the cache is empty. Call refresh() to update the cache.

Flag Overrides

With flag overrides you can overwrite the feature flags & settings downloaded from the ConfigCat CDN with local values. Moreover, you can specify how the overrides should apply over the downloaded values. The following 3 behaviours are supported:

  • Local/Offline mode (OverrideBehaviour.localOnly): When evaluating values, the SDK will not use feature flags & settings from the ConfigCat CDN, but it will use all feature flags & settings that are loaded from local-override sources.

  • Local over remote (OverrideBehaviour.localOverRemote): When evaluating values, the SDK will use all feature flags & settings that are downloaded from the ConfigCat CDN, plus all feature flags & settings that are loaded from local-override sources. If a feature flag or a setting is defined both in the downloaded and the local-override source then the local-override version will take precedence.

  • Remote over local (OverrideBehaviour.remoteOverLocal): When evaluating values, the SDK will use all feature flags & settings that are downloaded from the ConfigCat CDN, plus all feature flags & settings that are loaded from local-override sources. If a feature flag or a setting is defined both in the downloaded and the local-override source then the downloaded version will take precedence.

You can set up the SDK to load your feature flag & setting overrides from a [String: Any] dictionary.

let dictionary:[String: Any] = [
"enabledFeature": true,
"disabledFeature": false,
"intSetting": 5,
"doubleSetting": 3.14,
"stringSetting": "test"
]

let client = ConfigCatClient(
sdkKey: "<PLACE-YOUR-SDK-KEY-HERE>",
flagOverrides: LocalDictionaryDataSource(source: dictionary, behaviour: .localOnly)
)

Custom cache

You have the option to inject your custom cache implementation into the client. All you have to do is to inherit from the ConfigCache open class:

public class MyCustomCache : ConfigCache {
public func read(key: String) throws -> String {
// here you have to return with the cached value
// you can access the latest cached value in case
// of a failure like: super.inMemoryValue
}

public func write(key: String, value: String) throws {
// here you have to store the new value in the cache
}
}

Then use your custom cache implementation:

let client = ConfigCatClient(sdkKey: "<PLACE-YOUR-SDK-KEY-HERE>", configCache: MyCustomCache())

Force refresh

Any time you want to refresh the cached configuration with the latest one, you can call the refresh() method of the library, which will initiate a new fetch and will update the local cache.

Using ConfigCat behind a proxy

Provide your own network credentials (username/password), and proxy server settings (proxy server/port) by adding a ProxyDictionary to the ConfigCat's URLSessionConfiguration.

let proxyHost = "127.0.0.1"
let proxyPort = 8080
let configuration = URLSessionConfiguration.default
let proxyUser = "user"
let proxyPassword = "password"
configuration.connectionProxyDictionary = [
kCFNetworkProxiesHTTPEnable: true,
kCFNetworkProxiesHTTPProxy: proxyHost,
kCFNetworkProxiesHTTPPort: proxyPort,
kCFNetworkProxiesHTTPSEnable: true,
kCFNetworkProxiesHTTPSProxy: proxyHost,
kCFNetworkProxiesHTTPSPort: proxyPort,
kCFProxyUsernameKey: proxyUser, // Optional
kCFProxyPasswordKey: proxyPassword // Optional
]

let client: ConfigCatClient = ConfigCatClient(sdkKey: sdkKey, sessionConfiguration: configuration)

Changing the default HTTP timeout

Set the maximum wait time for a ConfigCat HTTP response by changing the timeoutIntervalForRequest of the ConfigCat's URLSessionConfiguration. The default timeoutIntervalForRequest is 60 seconds.

let configuration = URLSessionConfiguration.default
configuration.timeoutIntervalForRequest = 10; // Timeout in seconds

let client: ConfigCatClient = ConfigCatClient(sdkKey: sdkKey, sessionConfiguration: configuration)

Sensitive information handling

The frontend/mobile SDKs are running in your users' browsers/devices. The SDK is downloading a config.json file from ConfigCat's CDN servers. The URL path for this config.json file contains your SDK key, so the SDK key and the content of your config.json file (feature flag keys, feature flag values, targeting rules, % rules) can be visible to your users. This SDK key is read-only, it only allows downloading your config.json file, but nobody can make any changes with it in your ConfigCat account.

If you do not want to expose the SDK key or the content of the config.json file, we recommend using the SDK in your backend components only. You can always create a backend endpoint using the ConfigCat SDK that can evaluate feature flags for a specific user, and call that backend endpoint from your frontend/mobile applications.

Also, we recommend using confidential targeting comparators in the targeting rules of those feature flags that are used in the frontend/mobile SDKs.

Sample App

Check out our Sample Application how they use the ConfigCat SDK