gistfile1.txt

    self.permConstructor = function(perm) {

        return ko.computed({
                read: function(){self.hasPerm(perm)},
                write: function(val){
                    if (val) {
                        self.permissions.push(perm);
                    } else {
                        self.permissions.remove(perm);
                    }
                }
            });

    }

    self.presenter = self.permConstructor('canvas');
    self.sendAudio = self.permConstructor('audio');