Fix up memory leaks

Source/Constraint.swift

@@ -231,9 +231,12 @@ public class Constraint {
     }
     
     internal func activateIfNeeded(updatingExisting: Bool = false) {
-        let view = self.from.view!
+        guard let view = self.from.view else {
+            print("WARNING: SnapKit failed to get from view from constraint. Activate will be a no-op.")
+            return
+        }
         let layoutConstraints = self.layoutConstraints
-        let existingLayoutConstraints = view.snp.layoutConstraints
+        let existingLayoutConstraints = view.snp.constraints.map({ $0.layoutConstraints }).reduce([]) { $0 + $1 }
         
         if updatingExisting {
             for layoutConstraint in layoutConstraints {
@@ -247,14 +250,17 @@ public class Constraint {
             }
         } else {
             NSLayoutConstraint.activate(layoutConstraints)
-            view.snp.add(layoutConstraints: layoutConstraints)
+            view.snp.add(constraints: [self])
         }
     }
     
     internal func deactivateIfNeeded() {
-        let view = self.from.view!
+        guard let view = self.from.view else {
+            print("WARNING: SnapKit failed to get from view from constraint. Deactivate will be a no-op.")
+            return
+        }
         let layoutConstraints = self.layoutConstraints
         NSLayoutConstraint.deactivate(layoutConstraints)
-        view.snp.remove(layoutConstraints: layoutConstraints)
+        view.snp.remove(constraints: [self])
     }
 }

Source/ConstraintMaker.swift

@@ -180,7 +180,7 @@ public class ConstraintMaker {
     }
     
     internal static func updateConstraints(view: ConstraintView, closure: (_ make: ConstraintMaker) -> Void) {
-        guard view.snp.layoutConstraints.count > 0 else {
+        guard view.snp.constraints.count > 0 else {
             self.makeConstraints(view: view, closure: closure)
             return
         }
@@ -197,7 +197,7 @@ public class ConstraintMaker {
     }
     
     internal static func removeConstraints(view: ConstraintView) {
-        let constraints = view.snp.layoutConstraints.map { $0.constraint! }
+        let constraints = view.snp.constraints
         for constraint in constraints {
             constraint.deactivateIfNeeded()
         }

Source/ConstraintViewDSL.swift

@@ -100,36 +100,36 @@ public struct ConstraintViewDSL: ConstraintAttributesDSL {
         
     }
     
-    internal var layoutConstraints: [LayoutConstraint] {
-        return self.layoutConstraintsHashTable.allObjects
+    internal var constraints: [Constraint] {
+        return self.constraintsHashTable.allObjects
     }
     
-    internal func add(layoutConstraints: [LayoutConstraint]) {
-        let hashTable = self.layoutConstraintsHashTable
-        for layoutConstraint in layoutConstraints {
-            hashTable.add(layoutConstraint)
+    internal func add(constraints: [Constraint]) {
+        let hashTable = self.constraintsHashTable
+        for constraint in constraints {
+            hashTable.add(constraint)
         }
     }
     
-    internal func remove(layoutConstraints: [LayoutConstraint]) {
-        let hashTable = self.layoutConstraintsHashTable
-        for layoutConstraint in layoutConstraints {
-            hashTable.remove(layoutConstraint)
+    internal func remove(constraints: [Constraint]) {
+        let hashTable = self.constraintsHashTable
+        for constraint in constraints {
+            hashTable.remove(constraint)
         }
     }
     
-    private var layoutConstraintsHashTable: NSHashTable<LayoutConstraint> {
-        let layoutConstraints: NSHashTable<LayoutConstraint>
+    private var constraintsHashTable: NSHashTable<Constraint> {
+        let constraints: NSHashTable<Constraint>
         
-        if let existing = objc_getAssociatedObject(self.view, &layoutConstraintsKey) as? NSHashTable<LayoutConstraint> {
-            layoutConstraints = existing
+        if let existing = objc_getAssociatedObject(self.view, &constraintsKey) as? NSHashTable<Constraint> {
+            constraints = existing
         } else {
-            layoutConstraints = NSHashTable<LayoutConstraint>.weakObjects()
-            objc_setAssociatedObject(self.view, &layoutConstraintsKey, layoutConstraints, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
+            constraints = NSHashTable<Constraint>()
+            objc_setAssociatedObject(self.view, &constraintsKey, constraints, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
         }
-        return layoutConstraints
+        return constraints
         
     }
     
 }
-private var layoutConstraintsKey: UInt8 = 0
+private var constraintsKey: UInt8 = 0

Source/LayoutConstraint.swift

@@ -39,7 +39,7 @@ public class LayoutConstraint: NSLayoutConstraint {
         }
     }
     
-    internal var constraint: Constraint! = nil
+    internal weak var constraint: Constraint? = nil
     
 }