Gesture recognition (drag, magnify, rotate) in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a pan gesture recognizer to the view.

iOS Swift

let panGesture = UIPanGestureRecognizer(target: self, action: #selector(handlePan))
view.[1](panGesture)

Drag options to blanks, or click blank then click option'

AaddGestureRecognizer

BremoveGestureRecognizer

CbringSubviewToFront

DaddSubview

Attempts:

3 left

💡 Hint

Common Mistakes

Using addSubview instead of addGestureRecognizer

Trying to remove gesture recognizer instead of adding

To detect drag gestures, you add a UIPanGestureRecognizer to the view using addGestureRecognizer.

2fill in blank

medium

Complete the code to get the translation point from the pan gesture recognizer.

iOS Swift

let translation = sender.[1](in: view)

Drag options to blanks, or click blank then click option'

Atranslation

Bstate

Cvelocity

Dlocation

Attempts:

3 left

💡 Hint

Common Mistakes

Using location instead of translation

Using velocity which gives speed, not distance

The translation(in:) method gives the drag distance of the gesture in the view's coordinate system.

3fill in blank

hard

Fix the error in the magnification gesture handler to get the scale value.

iOS Swift

func handlePinch(_ sender: UIPinchGestureRecognizer) {
    let scale = sender.[1]
    view.transform = view.transform.scaledBy(x: scale, y: scale)
    sender.scale = 1.0
}

Drag options to blanks, or click blank then click option'

Alocation

Bvelocity

Ctranslation

Dscale

Attempts:

3 left

💡 Hint

Common Mistakes

Using velocity or translation instead of scale

Trying to call a method instead of accessing a property

The scale property of UIPinchGestureRecognizer gives the pinch scale factor.

4fill in blank

hard

Fill both blanks to get the rotation angle and apply it to the view transform.

iOS Swift

func handleRotation(_ sender: UIRotationGestureRecognizer) {
    let rotation = sender.[1]
    view.transform = view.transform.[2](by: rotation)
    sender.rotation = 0
}

Drag options to blanks, or click blank then click option'

Arotation

Bscale

Crotated

DscaledBy

Attempts:

3 left

💡 Hint

Common Mistakes

Using scale property for rotation

Using scaledBy method instead of rotated

The rotation property gives the rotation angle. The rotated(by:) method applies rotation to the transform.

5fill in blank

hard

Fill all three blanks to reset the view transform after gestures.

iOS Swift

func resetTransform() {
    UIView.animate(withDuration: [1]) {
        self.view.transform = CGAffineTransform.[2]()
    } completion: { _ in
        print("Transform [3]")
    }
}

Drag options to blanks, or click blank then click option'

A0.3

Bidentity

Creset

D0.5

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong duration value

Using non-existent transform methods

Printing wrong status message

Animation duration is 0.5 seconds. CGAffineTransform.identity() resets the transform. The print statement confirms the reset.