问如何防止angular-ui modal关闭？

EN

$modal.open({
   // ... other options
   backdrop  : 'static',
   keyboard  : false
});

backdrop : 'static'

keyboard :false

$scope.$on('modal.closing', function(event, reason, closed) {
    console.log('modal.closing: ' + (closed ? 'close' : 'dismiss') + '(' + reason + ')');
    var message = "You are about to leave the edit view. Uncaught reason. Are you sure?";
    switch (reason){
        // clicked outside
        case "backdrop click":
            message = "Any changes will be lost, are you sure?";
            break;

        // cancel button
        case "cancel":
            message = "Any changes will be lost, are you sure?";
            break;

        // escape key
        case "escape key press":
            message = "Any changes will be lost, are you sure?";
            break;
    }
    if (!confirm(message)) {
        event.preventDefault();
    }
});