how to throw SKSpriteNode?

Here is a quick example I wrote of moving a sprite with touch by simulating its velocity in the game-loop as opposed to setting the position directly. This makes the sprite more dynamic (i.e. you can “throw” it, and let it interact with other physics bodies as your drag the sprite). No angle calculations are needed, i’m simply calculating the necessary velocity to move the sprite to the touch position over some interval of time. In this case I set the time as 1/60 so that the motion is applied instantaneously so the object appears very responsive.

import SpriteKit
class GameScene: SKScene {
    var sprite: SKSpriteNode!
    var touchPoint: CGPoint = CGPoint()
    var touching: Bool = false
    override func didMoveToView(view: SKView) {
        self.physicsBody = SKPhysicsBody(edgeLoopFromRect: self.frame)
        sprite = SKSpriteNode(color: UIColor.redColor(), size: CGSize(width: 50, height: 50))
        sprite.physicsBody = SKPhysicsBody(rectangleOfSize: sprite.size)
        sprite.position = CGPoint(x: self.size.width/2.0, y: self.size.height/2.0)
        self.addChild(sprite)
    }
    override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
        let touch = touches.first as! UITouch
        let location = touch.locationInNode(self)
        if sprite.frame.contains(location) {
            touchPoint = location
            touching = true
        }
    }
    override func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
        let touch = touches.first as! UITouch
        let location = touch.locationInNode(self)
        touchPoint = location
    }
    override func touchesEnded(touches: Set<NSObject>, withEvent event: UIEvent) {
        touching = false
    }

    override func update(currentTime: CFTimeInterval) {
        if touching {
            let dt:CGFloat = 1.0/60.0
            let distance = CGVector(dx: touchPoint.x-sprite.position.x, dy: touchPoint.y-sprite.position.y)
            let velocity = CGVector(dx: distance.dx/dt, dy: distance.dy/dt)
            sprite.physicsBody!.velocity=velocity
        }
    }
}

You can fine-tune the phyiscs calculations yourself to get the desired effect you are looking for. But this code should be enough to get you started. Some enhancements I could think of are possibly capping the velocity so the object can’t move too fast when released. Adding a delay to the touch-drag so that moving the sprite but then accidentally stopping short at the end continues to throw the object.