Execute constraint copying asynchronously

This fixes crashes where the replaced constraint is sill retained by a trait collection but references a deallocated firstItem. See sunnyxx#29
dsmatter · Sep 18, 2016 · 42b732e · 42b732e
1 parent 57c6b77
commit 42b732e
Showing 1 changed file with 41 additions and 41 deletions.
diff --git a/XXNibBridge/XXNibBridge.m b/XXNibBridge/XXNibBridge.m
@@ -70,50 +70,50 @@ + (UIView *)instantiateRealViewFromPlaceholder:(UIView *)placeholderView {
 
     // Copy autolayout constrains.
     if (placeholderView.constraints.count > 0) {
-
-        // We only need to copy "self" constraints (like width/height constraints)
-        // from placeholder to real view
-        for (NSLayoutConstraint *constraint in placeholderView.constraints) {
-
-            NSLayoutConstraint* newConstraint;
-
-            // "Height" or "Width" constraint
-            // "self" as its first item, no second item
-            if (!constraint.secondItem) {
-                newConstraint =
-                [NSLayoutConstraint constraintWithItem:realView
-                                             attribute:constraint.firstAttribute
-                                             relatedBy:constraint.relation
-                                                toItem:nil
-                                             attribute:constraint.secondAttribute
-                                            multiplier:constraint.multiplier
-                                              constant:constraint.constant];
-            }
-            // "Aspect ratio" constraint
-            // "self" as its first AND second item
-            else if ([constraint.firstItem isEqual:constraint.secondItem]) {
-                newConstraint =
-                [NSLayoutConstraint constraintWithItem:realView
-                                             attribute:constraint.firstAttribute
-                                             relatedBy:constraint.relation
-                                                toItem:realView
-                                             attribute:constraint.secondAttribute
-                                            multiplier:constraint.multiplier
-                                              constant:constraint.constant];
-            }
-
-            // Copy properties to new constraint
-            if (newConstraint) {
-                newConstraint.shouldBeArchived = constraint.shouldBeArchived;
-                newConstraint.priority = constraint.priority;
-                if ([UIDevice currentDevice].systemVersion.floatValue >= 7.0f) {
-                    newConstraint.identifier = constraint.identifier;
+        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+            // We only need to copy "self" constraints (like width/height constraints)
+            // from placeholder to real view
+            for (NSLayoutConstraint *constraint in placeholderView.constraints) {
+                NSLayoutConstraint* newConstraint;
+
+                // "Height" or "Width" constraint
+                // "self" as its first item, no second item
+                if (!constraint.secondItem) {
+                    newConstraint =
+                    [NSLayoutConstraint constraintWithItem:realView
+                                                 attribute:constraint.firstAttribute
+                                                 relatedBy:constraint.relation
+                                                    toItem:nil
+                                                 attribute:constraint.secondAttribute
+                                                multiplier:constraint.multiplier
+                                                  constant:constraint.constant];
+                }
+                // "Aspect ratio" constraint
+                // "self" as its first AND second item
+                else if ([constraint.firstItem isEqual:constraint.secondItem]) {
+                    newConstraint =
+                    [NSLayoutConstraint constraintWithItem:realView
+                                                 attribute:constraint.firstAttribute
+                                                 relatedBy:constraint.relation
+                                                    toItem:realView
+                                                 attribute:constraint.secondAttribute
+                                                multiplier:constraint.multiplier
+                                                  constant:constraint.constant];
+                }
+
+                // Copy properties to new constraint
+                if (newConstraint) {
+                    newConstraint.shouldBeArchived = constraint.shouldBeArchived;
+                    newConstraint.priority = constraint.priority;
+                    if ([UIDevice currentDevice].systemVersion.floatValue >= 7.0f) {
+                        newConstraint.identifier = constraint.identifier;
+                    }
+                    [realView addConstraint:newConstraint];
                 }
-                [realView addConstraint:newConstraint];
             }
-        }
+        });
     }
-    
+
     return realView;
 }