---
title: VNRequest
framework: vision
role: symbol
role_heading: Class
path: vision/vnrequest
---

# VNRequest

The abstract superclass for analysis requests.

## Declaration

```swift
class VNRequest
```

## Overview

Overview Other Vision request handlers that perform image analysis inherit from this abstract base class. Instantiate one of its subclasses to perform image analysis. important: A VNRequest discards the alpha channel of input images, so don’t rely on it.

## Topics

### Initializing a Request

- [init()](vision/vnrequest/init().md)
- [init(completionHandler:)](vision/vnrequest/init(completionhandler:).md)

### Configuring a Request

- [VNRequestCompletionHandler](vision/vnrequestcompletionhandler.md)
- [completionHandler](vision/vnrequest/completionhandler.md)
- [preferBackgroundProcessing](vision/vnrequest/preferbackgroundprocessing.md)
- [results](vision/vnrequest/results.md)
- [revision](vision/vnrequest/revision.md)
- [usesCPUOnly](vision/vnrequest/usescpuonly.md)

### Configuring the Compute Device

- [setComputeDevice(_:for:)](vision/vnrequest/setcomputedevice(_:for:).md)
- [computeDevice(for:)](vision/vnrequest/computedevice(for:).md)
- [supportedComputeStageDevices](vision/vnrequest/supportedcomputestagedevices.md)

### Canceling a Request

- [cancel()](vision/vnrequest/cancel().md)

### Executing a Completion Handler

- [VNRequestCompletionHandler](vision/vnrequestcompletionhandler.md)

### Determining the Revision

- [VNRequestRevisionProviding](vision/vnrequestrevisionproviding.md)
- [currentRevision](vision/vnrequest/currentrevision.md)
- [defaultRevision](vision/vnrequest/defaultrevision.md)
- [supportedRevisions](vision/vnrequest/supportedrevisions.md)

## Relationships

### Inherits From

- [NSObject](objectivec/nsobject-swift.class.md)

### Inherited By

- [VNImageBasedRequest](vision/vnimagebasedrequest.md)

### Conforms To

- [CVarArg](swift/cvararg.md)
- [CustomDebugStringConvertible](swift/customdebugstringconvertible.md)
- [CustomStringConvertible](swift/customstringconvertible.md)
- [Equatable](swift/equatable.md)
- [Hashable](swift/hashable.md)
- [NSCopying](foundation/nscopying.md)
- [NSObjectProtocol](objectivec/nsobjectprotocol.md)

## See Also

### Still-image analysis

- [Detecting Objects in Still Images](vision/detecting-objects-in-still-images.md)
- [Classifying images for categorization and search](vision/classifying-images-for-categorization-and-search.md)
- [Analyzing Image Similarity with Feature Print](vision/analyzing-image-similarity-with-feature-print.md)
- [VNImageBasedRequest](vision/vnimagebasedrequest.md)
- [VNClassifyImageRequest](vision/vnclassifyimagerequest.md)
- [VNGenerateImageFeaturePrintRequest](vision/vngenerateimagefeatureprintrequest.md)
- [VNFeaturePrintObservation](vision/vnfeatureprintobservation.md)
- [VNImageRequestHandler](vision/vnimagerequesthandler.md)
- [VNObservation](vision/vnobservation.md)