Let the delegate provide the marchingSquares instance

Metaballs-macOS/ViewController.swift

@@ -38,6 +38,8 @@ class ViewController: NSViewController, RendererDelegate {
         }
     }
 
+    var marchingSquares: MarchingSquares
+
     private var renderer: Renderer!
 
     internal var metalView: MTKView {
@@ -47,12 +49,14 @@ class ViewController: NSViewController, RendererDelegate {
     override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
         let params = ViewController.defaultParameters()
         field = Field(parameters: params)
+        marchingSquares = MarchingSquares(field: field)
         super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
     }
 
     required init?(coder: NSCoder) {
         let params = ViewController.defaultParameters()
         field = Field(parameters: params)
+        marchingSquares = MarchingSquares(field: field)
         super.init(coder: coder)
     }
 
@@ -112,6 +116,7 @@ class ViewController: NSViewController, RendererDelegate {
         }
         set {
             field.size = newValue
+            marchingSquares.fieldDidResize()
         }
     }
 }

MetaballsKit/Metaballs.swift

@@ -109,7 +109,6 @@ public class Field {
                 // Update Metal state as needed.
                 populateParametersBuffer()
                 populateBallBuffer()
-                marchingSquares.fieldDidResize()
 
                 parameters.size = newValue
             }
@@ -120,9 +119,6 @@ public class Field {
 
     public var defaults = UserDefaults.standard
     private var parameters: Parameters
-    lazy var marchingSquares: MarchingSquares = {
-        return MarchingSquares(field: self)
-    }()
 
     internal var bounds: CGRect {
         return CGRect(origin: CGPoint(), size: CGSize(size: size))
@@ -263,7 +259,7 @@ public class Field {
         return ptr.advanced(by: sizeOfType)
     }
 
-    public func setupMetal(withDevice device: MTLDevice) throws {
+    func setupMetal(withDevice device: MTLDevice) {
         guard self.device == nil else {
             return
         }
@@ -271,7 +267,6 @@ public class Field {
         self.device = device
         populateParametersBuffer()
         populateBallBuffer()
-        marchingSquares.setupMetal(withDevice: device)
     }
 
     // MARK: - Notifications

MetaballsKit/Renderer.swift

@@ -13,9 +13,10 @@ public enum RendererError: Error {
     case MetalError(String)
 }
 
-public protocol RendererDelegate {
+protocol RendererDelegate {
     var renderSize: Size { get set }
     var field: Field { get }
+    var marchingSquares: MarchingSquares { get }
     var metalView: MTKView { get }
 }
 
@@ -29,7 +30,7 @@ struct Vertex {
 }
 
 public class Renderer: NSObject, MTKViewDelegate {
-    public var delegate: RendererDelegate? = nil {
+    var delegate: RendererDelegate? = nil {
         didSet {
             guard let delegate = delegate else {
                 return
@@ -41,7 +42,8 @@ public class Renderer: NSObject, MTKViewDelegate {
             configurePixelPipeline(withPixelFormat: view.colorPixelFormat)
             configureMarchingSquaresPipeline(withPixelFormat: view.colorPixelFormat)
 
-            try! delegate.field.setupMetal(withDevice: device)
+            delegate.field.setupMetal(withDevice: device)
+            delegate.marchingSquares.setupMetal(withDevice: device)
         }
     }
 
@@ -80,7 +82,7 @@ public class Renderer: NSObject, MTKViewDelegate {
         super.init()
     }
 
-    public convenience init(delegate: RendererDelegate) throws {
+    convenience init(delegate: RendererDelegate) throws {
         self.init()
         self.delegate = delegate
     }
@@ -223,6 +225,7 @@ public class Renderer: NSObject, MTKViewDelegate {
                 didEncode = true
             }
 
+            if let marchingSquares = delegate?.marchingSquares {
                 // Render the marching squares version over top of the pixel version.
                 // We need our own render pass descriptor that specifies that we load the results of the previous pass to make this render pass appear on top of the other.
                 let pass = renderPass.copy() as! MTLRenderPassDescriptor
@@ -231,13 +234,14 @@ public class Renderer: NSObject, MTKViewDelegate {
                     let encoder = buffer.makeRenderCommandEncoder(descriptor: pass) {
                     encoder.label = "Marching Squares Render"
                     encoder.setRenderPipelineState(pipeline)
-                encoder.setVertexBuffer(field.marchingSquares.gridGeometry, offset: 0, index: 0)
+                    encoder.setVertexBuffer(marchingSquares.gridGeometry, offset: 0, index: 0)
                     encoder.setVertexBuffer(parametersBuffer, offset: 0, index: 1)
-                encoder.drawPrimitives(type: .line, vertexStart: 0, vertexCount: field.marchingSquares.gridVertexCount)
+                    encoder.drawPrimitives(type: .line, vertexStart: 0, vertexCount: marchingSquares.gridVertexCount)
                     encoder.endEncoding()
                     didEncode = true
                 }
             }
+        }
 
         if didEncode, let drawable = view.currentDrawable {
             buffer.present(drawable)