# Key Concepts

In the following use case sections, we will guide you through the most common usage scenarios and reveal tips and easy-to-understand guidelines to help you get the most out of the HERE SDK for iOS.

## How to use this Guide?

You can read this guide in any order. All sections are independent from each other, making it easy to skip any section and to dive straight into the topics which you are most interested in.

• In the example section, you can find the example apps accompanying this user guide.
• If you are interested in building your first app showing a HERE map, take a look at the Get Started section to guide you through the first simple steps.

## Conventions

The HERE SDK uses completion handlers as callback functions. For all completion handlers available in the HERE SDK, you can either use closure expressions or function call expressions. By convention, for this guide, we preferably use function call expressions to show the full type of information and other details, such as method and callback name. An example for both can be found in the Search section.

### Completion Handlers and Delegates

• The HERE SDK uses completion handlers for single event notification such as for search results.
• For reoccurring event notifications such as for gesture events, delegates are used. When multiple delegates can be set, then the method pattern add_x() and remove_x() is used as naming convention. If only one delegate can be set at a time, properties are used that can be set to nil to stop listening.

### Debug Logs

You can use the LogAppender protocol to insert your own log class into the SDKNativeEngine. This way you can log HERE SDK messages for various predefined log levels even for release builds of your app.

### Code Snippets

The shown code snippets cover best practice example code ready to be used for your own applications. However, for the sake of simplicity and to not shadow the educational approach of this guide, not all edge scenarios may be handled, especially when it comes to error handling or robust threading. In some cases, the obvious code is left out, but it can be found in the accompanying example apps that can be instantly built and deployed on any supported device - given a set a of valid HERE credentials. As is the practice in Swift, forced unwrapping of optionals is avoided except when the HERE SDK guarantees by design that it is safe to do so.

### Design Principles

The accompanying example apps follow the same structure. As much as possible the HERE SDK example code is decoupled from the surrounding platform code. We hope this makes it easier to see the relevant parts of the shown APIs. Each example app follows the same entry point from which the HERE SDK is initialized. Since each app is focusing on a different aspect of the HERE SDK, that code can be found in a single class postfixed with "...Example.swift" in its class name. Most often this class gets a reference to a MapView to start its work.

Following a common platform separation principle, the example code is kept free of most iOS dependencies - instead it's mostly pure Swift code that shows how the HERE SDK can be used.

## Is the HERE SDK Thread Safe?

The HERE SDK is not guaranteed to be thread safe and it is recommended to make calls to the SDK from the main thread. Internally, the HERE SDK will offload most of its work to a background thread, but callbacks to your code will always occur on the main thread. In general, thread safety is the responsibility of the caller. For example, it is unsafe to reuse an engine on different threads unless your code is synchronized.

## Engines

The HERE SDK contains several modules - or engines as we call them - to execute specific tasks such as calculating a route with the RoutingEngine or requesting search results via the SearchEngine. There are many more engines you can use with the HERE SDK and you can read more about them in the dedicated chapters below. However, most engines share common concepts that makes it easier to use them. For example:

• All engines share similar interfaces, callbacks and error handling.
• It is possible to start multiple instances of an engine in parallel.
• An online connection is required.

### Use TaskHandles to Cancel Asynchronous Operations

Most asynchronous methods provide a TaskHandle as immediate return value, while the final result of the operation will be returned in a completion handler with a delay. The TaskHandle provides status information and it allows to abort an ongoing operation.

### Set HERE Credentials from Property List or Programmatically

Usually, engines can operate independently from each other and require HERE credentials to request data. The credentials can be set in the Info.plist file as shown in the Get Started guide - or programmatically. This can be useful, for example, to inject credentials at runtime from a web service.

By default, when using a map view in your app, the HERE SDK is initialized automatically and it is reading the credentials from the Info.plist file. In addition, a default cache path is used for caching map data.

### Use SDKOptions to set HERE Credentials and Cache Path

When you want to set the credentials programmatically, you must take care to initialize the HERE SDK yourself. A good place to do this is the AppDelegate after application launch - before the MapView is initialized and any other parts of the HERE SDK are used:

do {
try SDKInitializer.initializeIfNecessary()
} catch {
fatalError("Failed to initialize HERE SDK. Cause: \(error)")
}


As a next step, you need to create your own instance of the SDKNativeEngine, which can then be used to set or to change your HERE SDK credentials at runtime:

let cachePath = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first?.path ?? ""
let sdkOptions = SDKOptions(accessKeyId: "YOUR_ACCESS_KEY_ID",
accessKeySecret: "YOUR_ACCESS_KEY_SECRET",
cachePath: cachePath)

var sdkNativeEngine: SDKNativeEngine
do {
try sdkNativeEngine = SDKNativeEngine(options: sdkOptions)
} catch let engineInstantiationError {
fatalError("Failed to initialize engine. Cause: \(engineInstantiationError)")
}

SDKNativeEngine.sharedInstance = sdkNativeEngine

do {
try searchEngine = SearchEngine()
} catch let engineInstantiationError {
fatalError("Failed to initialize engine. Cause: \(engineInstantiationError)")
}


This allows you to set a shared instance that will then be used for all engines under the hood. Above, we initialize the SearchEngine as an example. Note that a shared instance is also required when you add a map view.

By setting an empty string as cache path, you keep the default cache path - which is also accessible via SDKNativeEngine.sharedInstance?.options.cachePath.

Note: It is also possible to specify the cache path from the Info.plist file. Consult the API Reference for the SDKNativeEngine to see an example.

Multiple SDKNativeEngine instances can’t have the same access key id and the cache path is ensured to be unique per access key id. After creating a new SDKNativeEngine, the access key id cannot be changed. Only the secret key can be changed afterwards.

Since turn-by-turn navigation requires caching, a valid cache path should be set when manually creating a SDKNativeEngine.

Alternatively, you can set the engine individually for each engine:

try searchEngine = SearchEngine(sdkNativeEngine)


By default, the HERE SDK's SDKInitializer will still look for the credentials in your Info.plist file. Therefore, when setting credentials programmatically, keep the tags holding dummy values for id and secret, like shown in the snippet below. Empty values will lead to an exception:

<key>HERECredentials</key>
<dict>
<key>AccessKeyId</key>
<string>cdefgabc</string>
<key>AccessKeySecret</key>
<string>cdefgabc</string>
</dict>


If you don't set your credentials programmatically, the HERE SDK will be initialized automatically using the values found in the Info.plist. Either way, invalid credentials will not block execution until these credentials are used to authenticate your app when you start to use an engine to request data - or when you want to show a map view.

Tip: One option to keep credentials secure is to store them on a secure server and retrieve them by requests using SSL connections. Credentials stored in Info.plist are easy to unveil, a better option can be to use Keychain data protection.

For best practice, consider:

• To avoid keeping sensitive data in plain text.
• To transfer credentials using a secure communication channel.
• To store credentials using device security and strong encryption ciphers.
• To add anti-tampering and anti-debugging code, so that a potential attacker cannot intercept data during dynamic runtime execution.
• Track the application usage to detect anomalies.

### Use Engines with or without a Map View

It is possible to run an engine as a stand-alone, which means that you do not need to add a map view to your application. This way, you can build an app solely around a specific engine. If you are using an engine as a stand-alone, you must take care to initialize the HERE SDK yourself - as shown above. Then you can proceed to create a new engine. With or without a map view - the procedure to create a new engine is exactly the same:

do {
try searchEngine = SearchEngine()
} catch let engineInstantiationError {
fatalError("Failed to initialize engine. Cause: \(engineInstantiationError)")
}


When you use the default constructor to initialize an engine for stand-alone usage, the HERE SDK will use a shared SDKNativeEngine under the hood to take the credentials as found in the Info.plist file. Alternatively, you can provide the credentials programmatically as shown in the previous section.

## Maps

One of the core features of the HERE SDK for iOS is Mapping, which includes adding a map view, changing the location displayed by the map, and modifying its properties. The primary component of the mapping API is the map view, which is integrated as a UIView subclass. The map view represents a vector based view to display a map and various properties.

HERE map data is updated on a weekly basis to ensure you always get the freshest map data available. By integrating the map view you can automatically benefit from this.

Note: To create a simple map application, please refer to the Get Started section.

To manipulate the map and its properties it's best to start looking at the Camera section. More features include:

• Map gestures to handle common map gestures and default map behaviors like pan or rotate.
• Map schemes to instantly switch default map styles such as satellite versus normal map layer.
• Map items to place objects and shapes onto the map and interact with them.
• Custom map styles to load custom map schemes.

### HERE Logo Watermark

When using the HERE SDK, it is required that the HERE logo is always visible on the map view. By default, the HERE logo is located at the bottom right corner of the map. However, you can easily customize its location to meet your app design by calling setWatermarkPosition() on your map view instance. It is recommended to change the default placement only when it is required due to overlapping UI elements. Note for very small views: If both edges of the map are less than 250 density independent pixels in size, the watermark will be hidden automatically.

### Remove Unused Font Files

The HERE SDK contains fonts to render map labels for all supported languages. If you want to optimize the size of the overall app, you can remove selected fonts. For example, the font with Chinese, Japanese and Korean characters is around 1.7MB. To remove this font, open the heresdk.framework file and remove the following files:

• style/fonts/DroidSansFallback.woff
• style/fonts/DroidSansFallback.license

When you remove a font, it is recommended to switch the map language to any other language than the removed font. At least one font needs to be left to see any map labels. Note that each time a label needs to be displayed in a language for a font that was removed an error message is logged - for each character that is missing.

### Map Language

You can customize the language that is used on the map to show labels for streets, cities and other map data. By default, the local language of a region is used.

Call mapView.primaryLanguage = languageCode to set the language for the world - or set nil to switch back to the default behavior. If a language is not supported in any region of the world, the local language for that region is shown instead.

### Availability of Map Data

By default, a few regions in the world including Japan, China and Korea, contain limited map data. To get access to the full map data, please get in contact with your HERE representative.

### Offline Maps

All map data can be preloaded before usage (also known as active or explicit downloading) or downloaded during online usage (also known as passive or implicit downloading). Both of these strategies require a network connection for data download, but the explicit strategy allows to prepare data in advance and to consume it when a device doesn't have a network connection - while the implicit strategy uses a cache, which can be overwritten during map usage.

### Map Caching

To better support online and offline use cases, the HERE SDK for iOS supports caching of downloaded vector map data. This happens in the background. While interacting with the map, the data is stored locally on the device and can be accessed even when the device loses connection or operates in an offline mode.

The integrated map caching mechanism only supports the standard vector based map schemes - satellite images, for example, are not cached.

Please note that the amount of cached data is limited and will be overwritten with new map data while using the map. In most cases, this is sufficient to give the user the impression of a faster start-up time - as no additional data must be downloaded when you start an app again at the same location as before.

## Indoor Map

The HERE SDK provides the possibility to load, show and interact with private venues on the map. The HERE Indoor Map feature provides a wealth of hyperlocal information about indoor spaces, including building geometry and points of interest, spanning across multiple floors. HERE has mapped thousands of buildings globally, including, shopping malls, airports, train stations, parking garages, corporate campuses, factories, warehouses and many other types of buildings.