Display value in a field but don't save to model - angularjs

Question

Let's say I have an input, like this:
<input ng-model="myinput" />
I want it to display a default value of Hello on page load/render but not touch myinput.
I can't use a placeholder since I want the user to have the ability to edit the default value of hello. Once that default value is changed by the user, then that change should be reflected in myinput.
Anyone have any ideas?
Edit: For context, these input field default values are settings that the user saved which are being displayed on an item page. If the default value is saved to the model and the item is updated, then that default value sticks. Meaning, if they change the setting, then that item won't have the new setting value. Only if the user explicitly changed the field should it save that data to the item.

Answer 1

If I understand you correctly, one way of doing this is like this:
$scope.myinput= '';
$scope.tempVal = "some default value";
$scope.$watch('tempVal', function(newValue, oldValue) {
if (newValue != "some default value") {
$scope.myinput= newValue;
}
});
in the html:
<input type="text" ng-model="tempVal" />
you use a temp variable for the input and only when the value is not the default change myinput
note:
Are you sure you don't want to save the default value in the variable? I find it hard to imagine a use case in which it's not the best approach. Can you describe your use case?

Answer 2

Initialize myinput inside of your controller:
JavaScript
app.controller('ctrl', function($scope) {
$scope.myinput = 'hello';
});
HTML
<div ng-controller='ctrl'>
<input ng-model="myinput" />
</div>

Answer 3

I write a directive base on how I understand the requirement , hope it can help:
https://jsfiddle.net/tm5yv4Lk/
angular.module('myApp',[])
.controller('MainController', ['$scope', function($scope) {
$scope.myinput = 'my text';
$scope.myFakeInput = 'fake text';
}])
.directive('inputMask', ['$timeout', function($timeout) {
return {
restrict: 'A',
require: 'ngModel',
scope: {
inputMask: '='
},
link: function(scope, element, attrs, ctrl ) {
$timeout(function() {
element[0].value = scope.inputMask;
}, 0);
}
};
}]);
HTML:
<input ng-model="myinput" input-mask="myFakeInput"/>