Open Radar

 
Summary:
The field nodes returned by the electricField, magneticField and customFieldWithEvaluationBlock: don't do anything. In particular, the evaluation block for the custom field is never called, even when there is a node with a compatible fieldBitMask within the field.

Steps to Reproduce:
1. Create a new Sprite Kit project.
2. In the scene's didMoveToView method, create a node with a physics body and add it to the scene.
3. In the scene's didMoveToView method, create a custom field node with an evaluation block that prints a statement to the log and then returns a constant vector. Add the field to the scene.
4. Run the project.

Expected Results:
Many repeated log statements that indicate that the block has been called, and the node moving according to the vector returned by the block.

Actual Results:
Nothing.