function restrict($parse) {
var inputTypes = {
    textNumber: '[^A-Za-z0-9 _-ñÑáéíóúÁÉÍÓÚ]',
    text: '[^A-Za-z ñÑáéíóúÁÉÍÓÚ]',
    number: '[^0-9]',
    email: '[^A-Za-z.@]',
    basicTextNumber: '[^A-Za-z0-9_-]'
};

var link = function($scope, $element, $attrs) {
    var exp = inputTypes[$attrs.restrict] || $attrs.restrict;
    $scope.$watch($attrs.ngModel, function(value) {
        if (!value) {
            return;
        }
        if (typeof value === 'number') { // eslint-disable-line
            value = String(value);
        }
        $parse($attrs.ngModel).assign($scope, value.replace(new RegExp(exp, 'g'), ''));
    });
};

return {
    restrict: 'A',
    require: 'ngModel',
    link: link
};

<div class="row">
                <div class="input-field col s6">
                    <input class="validate" type="text" name="nombre" ng-model="vm.users.nombre" ng-minlength="2" restrict="text" maxlength=40 data-length=40 required autocomplete="off">
                    <label ng-class="active" for="nombre">Nombre</label>

                    <div role="alert" style="color:maroon" ng-show="!registro.nombre.$pristine">
                        <span class="error" ng-show="registro.nombre.$error.required">
                            Requerido</span>
                        <span class="error" ng-show="registro.nombre.$error.minlength">
                            Minimo 2 caracteres</span>
                    </div>

                </div>
            </div>