From 3f529652a4cfa463b7b4bc5cee06c5f9ac9d0887 Mon Sep 17 00:00:00 2001
From: vhosune <vhosune@gmail.com>
Date: Fri, 23 Sep 2016 12:54:49 +0200
Subject: [PATCH] =?UTF-8?q?fix=20"Mutating=20a=20priority=20from=20require?=
 =?UTF-8?q?d=20to=20not=20on=20an=20installed=20constra=E2=80=A6=20(#323)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* fix "Mutating a priority from required to not on an installed constraint (or vice-versa) is not supported." when the priority is not changed

* add more check when changing layout constraint priority

* add more lenient check when changing layout constraint priority

* fix UILayoutPriorityRequired available only on iOS

* fix undeclared UILayoutPriority on macOS

* add check for tvOS
---
 Source/Constraint.swift | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/Source/Constraint.swift b/Source/Constraint.swift
index b93a8d9..7324c59 100644
--- a/Source/Constraint.swift
+++ b/Source/Constraint.swift
@@ -228,7 +228,17 @@ public class Constraint {
         for layoutConstraint in self.layoutConstraints {
             let attribute = (layoutConstraint.secondAttribute == .notAnAttribute) ? layoutConstraint.firstAttribute : layoutConstraint.secondAttribute
             layoutConstraint.constant = self.constant.constraintConstantTargetValueFor(layoutAttribute: attribute)
-            layoutConstraint.priority = self.priority.constraintPriorityTargetValue
+            
+            #if os(iOS) || os(tvOS)
+                let requiredPriority: UILayoutPriority = UILayoutPriorityRequired
+            #else
+                let requiredPriority: Float = 1000.0
+            #endif
+            
+            
+            if (layoutConstraint.priority < requiredPriority), (self.priority.constraintPriorityTargetValue != requiredPriority) {
+                layoutConstraint.priority = self.priority.constraintPriorityTargetValue
+            }
         }
     }