Class

VNRequest

The abstract superclass for analysis requests.

Declaration

class VNRequest : NSObject

Overview

Other Vision request handlers that perform image analysis inherit from this abstract base class. Instantiate one of its subclasses to perform image analysis.

Topics

Initializing a Request

init()

Creates a new Vision request with no completion handler.

init(completionHandler: VNRequestCompletionHandler? = nil)

Creates a new Vision request with an optional completion handler.

Configuring a Request

var completionHandler: VNRequestCompletionHandler?

The completion handler block that's invoked after the request has finished processing.

var preferBackgroundProcessing: Bool

A hint to minimize the resource burden of the request.

var results: [Any]?

The collection of VNObservation results generated by request processing.

var usesCPUOnly: Bool

A Boolean signifying that the Vision request should execute exclusively on the CPU.

var revision: Int

The specific algorithm or implementation revision that is to be used to perform the request.

Executing a Completion Handler

typealias VNRequestCompletionHandler

A type alias to encapsulate the syntax for the completion handler block that's invoked after the request has finished processing.

Determining Revision

class var currentRevision: Int

The current revison supported by the request.

class var defaultRevision: Int

The revision of the latest request for the particular SDK linked with the client application.

class var supportedRevisions: IndexSet

The collection of currently-supported algorithm versions for the class of request.

Relationships

Inherits From

See Also

Still Image Analysis

Detecting Objects in Still Images

Locate and demarcate rectangles, faces, barcodes, and text in images using the Vision framework.

class VNImageRequestHandler

An object that processes one or more image analysis requests pertaining to a single image.

class VNImageBasedRequest

The abstract superclass for image analysis requests that focus on a specific part of an image.

class VNObservation

The abstract superclass for analysis results.