SKPhysicsJointSpring spring length?

I want to tap the screen and have a sort of grappling hook pull the player to the location. I’m using physics bodies, and a SKPhysicsJointSpring. This sort of works. The problem is the length of the spring is too long. I need to be able to set the distance between the anchor and the player object.

The blue square is a static object, placed on tap. The red box is a player. The two are connected with a SKPhysicsJointSpring. The length of the spring is always the same. In my text file the red box will swing from the blue anchor nicely. I need to be able to control the distance.

Turns out the length of the spring is set by the initial distance between the two bodies.