angularjs validate input and prevent change if invalid

Question

I neeed an input field where I can enter only the values 1,2 or 3 so i\'m trying to build a directive which prevents all changes to the model if it doesn\'t match these valu

Answer 1

I recently wrote a directive just for this. It takes a regExp object that validates the incoming key presses and only permits them if are valid:

// forces keystrokes that satisfy the regExp passed
app.directive("regExpRequire", function() {

    var regexp;
    return {
        restrict: "A",
        link: function(scope, elem, attrs) {
            regexp = eval(attrs.regExpRequire);

            var char;
            elem.on("keypress", function(event) {
                char = String.fromCharCode(event.which)
                if(!regexp.test(elem.val() + char))
                    event.preventDefault();
            })
        }
    }

})

Template usage:

Or in your case: