How do I find an angle with a swipe in Xcode 6 with SpriteKit?

Question

I'm making two games and for both I want to know how I can find an angle from a swipe. I've heard you use UIPanGesutre but I don't know how to use it. Any help?

Answer 1

You can detect the start and stop location coordinates of the touch and calculate the angle with the two points.

Answer 2

Within the touchesBegan event, determine the touch location:

Create an instance variable called initialLocation of type CGPoint in your interface

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
    //Determine touch location and store in instance variable (so you can use it again in touchesEnded)
    UITouch *touch = [touches anyObject];
    initialLocation = [touch locationInNode:self];
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{
    //Determine touch location
    UITouch *touch = [touches anyObject];
    CGPoint finalLocation = [touch locationInNode:self];

    //Find change in x and y between the touches
    CGFloat changeX = finalLocation.x - initialLocation.x;
    CGFloat changeY = finalLocation.y - initialLocation.y;

    //Use trig to find angle (note this angle is in radians)
    float radians = atan(changeY/changeX);

    //Convert to degrees
    float degrees = 360 * radians/(2 * M_PI);

    //*Note* you would have to alter this part depending on where you are measuring your angle from (I am using the standard counterclockwise from right)
    //This step is due to the limitation of the atan function
    float angle;
    if (changeX > 0 && changeY > 0){
        angle = degrees;
    }
    else if (changeX < 0 && changeY > 0){
        angle = 180 + degrees;
    }
    else if (changeX < 0 && changeY < 0){
        angle = 180 + degrees;
    }
    else{
        angle = 360 + degrees;
    }
    NSLog(@"Now: %f",angle);
    //^^^ HERE IS THE ANGLE! ^^^

}

I hope this helps!