Open Radar

 
Summary:
SCNIKConstraint provides two initialization mechanisms: an initializer and a class method (i.e. factory method). The factory method works, and the initializer fails with EXC_BAD_ACCESS, but the documentation doesn’t mention this.

Steps to Reproduce:
1. Run this code in an iOS playground or app. I’m using iOS 12.1.

import SceneKit

let node1 = SCNNode()
let ikConstraint1 = SCNIKConstraint.inverseKinematicsConstraint(chainRootNode: node1)

let node2 = SCNNode()
let ikConstraint2 = SCNIKConstraint(chainRootNode: node2) // EXC_BAD_ACCESS

Expected Results:
No crash. The lines behave identically.

Actual Results:
EXC_BAD_ACCESS when using the initializer. In all the examples I’ve tried, replacing the initializer with the class function makes everything start working.

Version:
Xcode 10.1 (10B61) on macOS 10.14.2 (18C54)

Notes:
The declarations are basically identical, and the docs don’t mention anything that might be amiss. Here’s the generated Swift interface for iOS 12.1:

    /*!
     @method initWithChainRootNode:
     @abstract Creates and returns a SCNIKConstraint object with the specified parameter.
     @param chainRootNode The root node of the kinematic chain.
     @discussion "chainRootNode" must be an ancestor of the node on which the constraint is applied.
     */
    @available(watchOS 2.0, *)
    public init(chainRootNode: SCNNode)

    
    /*!
     @method inverseKinematicsConstraintWithChainRootNode:
     @abstract Creates and returns a SCNIKConstraint object with the specified parameter.
     @param chainRootNode The root node of the kinematic chain.
     @discussion "chainRootNode" must be an ancestor of the node on which the constraint is applied.
    */
    open class func inverseKinematicsConstraint(chainRootNode: SCNNode) -> Self