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# SKAdImpression

A class that defines an ad impression for a view-through ad.

```
class SKAdImpression
```

## Overview

Create a `SKAdImpression` instance when you’re preparing to present a view-through ad. In the instance, you set:

- Values known to you, including your ad network ID, the App Store IDs of the source app and the advertised app, and the version.
- A value you determine – the campaign ID.
- Values you generate, including the timestamp, a nonce (ad-impression identifier), and the cryptographic signature.

For information about generating the cryptographic signature, see [Generating the signature to validate view-through ads](/documentation/StoreKit/generating-the-signature-to-validate-view-through-ads).

Use your `SKAdImpression` instance when you call [`startImpression(_:completionHandler:)`](/documentation/StoreKit/SKAdNetwork/startImpression(_:completionHandler:)) to begin presenting your view-through ad. Use the same instance when you call [`endImpression(_:completionHandler:)`](/documentation/StoreKit/SKAdNetwork/endImpression(_:completionHandler:)) to end the ad presentation.

## Topics

### Providing a signature

[`signature`](/documentation/StoreKit/SKAdImpression/signature)

The advertising network’s cryptographic signature for the ad impression.

### Creating a signature

[`init(sourceAppStoreItemIdentifier:advertisedAppStoreItemIdentifier:adNetworkIdentifier:adCampaignIdentifier:adImpressionIdentifier:timestamp:signature:version:)`](/documentation/StoreKit/SKAdImpression/init(sourceAppStoreItemIdentifier:advertisedAppStoreItemIdentifier:adNetworkIdentifier:adCampaignIdentifier:adImpressionIdentifier:timestamp:signature:version:))

Creates an ad impression object using the supplied values.

[`version`](/documentation/StoreKit/SKAdImpression/version)

The version of the SKAdNetwork API.

[`adNetworkIdentifier`](/documentation/StoreKit/SKAdImpression/adNetworkIdentifier)

A string that represents the advertising network’s unique identifier.

[`sourceIdentifier`](/documentation/StoreKit/SKAdImpression/sourceIdentifier)

A four-digit integer that ad networks define to represent the ad campaign.

[`adCampaignIdentifier`](/documentation/StoreKit/SKAdImpression/adCampaignIdentifier)

A number that represents the advertising network’s campaign.

[`advertisedAppStoreItemIdentifier`](/documentation/StoreKit/SKAdImpression/advertisedAppStoreItemIdentifier)

The App Store ID of the app that the ad impression advertises.

[`adImpressionIdentifier`](/documentation/StoreKit/SKAdImpression/adImpressionIdentifier)

A random value to use for added security.

[`sourceAppStoreItemIdentifier`](/documentation/StoreKit/SKAdImpression/sourceAppStoreItemIdentifier)

The App Store ID of the app that displays the ad.

[`timestamp`](/documentation/StoreKit/SKAdImpression/timestamp)

A number that represents the UNIX time, in milliseconds, of the ad impression.

### Describing ads

[`adType`](/documentation/StoreKit/SKAdImpression/adType)

The type of the ad.

[`adDescription`](/documentation/StoreKit/SKAdImpression/adDescription)

A human-readable description of the ad.

[`adPurchaserName`](/documentation/StoreKit/SKAdImpression/adPurchaserName)

The name of the entity that purchased the ad.


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