Using Swift 3D touch force value to change volume of a sound

Question

I'm trying to use the 3D touch force value to change the volume of my AVAudioUnitSampler when a button is pressed depending on how much force is used.

This is my current code to get the force value

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    if let touch = touches.first {
        print(touch.force)
    }
}

The problem is that sometimes when I press really hard on my phone (using iPhone 7 plus as physical device) I'm getting 0.0. Sometimes I'll get something greater than 0.0 but it's a problem when I press really hard and get 0.0.

Is my approach to what I'm trying accomplish a good way to do this or is there a better way?

Answer 1

Its generally easier to use a gesture recognizer, but you can still use the UIResponder touch methods; however you are using the wrong one. touchesBegan is only going to give you the force at the beginning of the touch when the force is very likely to be 0 or close to it. You need to get updates throughout the whole touch so you want touchesMoved. Of course you then have to decide if the touch has moved too much or if just the pressure has changed, which is why its easier to use UILongPressGestureRecognizer; it does this for you.