Improved performance for cases where a single expression is used for multiple fields. Also improved demo

Author: Kent C. Dodds

src/directives/formly-form.js

@@ -17,15 +17,23 @@ angular.module('formly.render')
 					//Post gets called after angular has created the FormController
 					//Now pass the FormController back up to the parent scope
 					scope.formOnParentScope = scope[attr.name];
+
+					var watches = {};
 					angular.forEach(scope.fields, function(field) {
 						if (field.hideExpression) {
-						var getter = $parse(field.hideExpression);
+							watches[field.hideExpression] = watches[field.hideExpression] || [];
+							watches[field.hideExpression].push(field);
+						}
+					});
+					angular.forEach(watches, function(fields, expression) {
+						var getter = $parse(expression);
 						scope.$watch(function() {
 							return getter(scope.result);
 						}, function(hide) {
-							field.hide = hide;
+							angular.forEach(fields, function(field) {
+								field.hide = hide;
+							});
 						});
-						}
 					});
 				}
 			}

src/views/home.js

@@ -147,7 +147,20 @@ app.controller('home', function($scope, $parse, $rootScope) {
 		key: 'hiddenWhenUnchecked',
 		type: 'text',
 		label: 'Conditional input',
+		placeholder: 'These both use the same hideExpression...',
 		hideExpression: '!checkThis'
+	}, {
+		key: 'hiddenWhenUnchecked2',
+		type: 'text',
+		label: 'Type "joe" in here',
+		placeholder: '... so there is only one $watch for both of them',
+		hideExpression: '!checkThis'
+	}, {
+		key: 'showWhenJoe',
+		type: 'text',
+		label: 'You typed Joe! You found me!',
+		placeholder: 'Different hideExpression, different $watch',
+		hideExpression: 'hiddenWhenUnchecked2 !== "joe"'
 	}, {
 		key:'secretCode',
 		type: 'hidden',