解决方法
找到解决方案：将自定义指令添加到ui-select元素,该元素在项目列表的底部手动添加.
代码(它包含一些额外的属性和功能,而不是在主题中描述.我按原样发布)：
.directive('customOption',function($timeout){
return {
restrict: 'A',link: function(scope,el,attrs){
var options = JSON.parse(attrs.customOption);
var buttonText = options.buttonText;
var func = options.click;
var type = options.type;
var condition = options.showIf;
var template = "<div class='custom-option-container'><button type='button' class='btn btn-primary'><span class='glyphicon glyphicon-plus-sign'></span>" + buttonText + "</button></div>";
//if condition evaluated to true or no condition
if(scope.$eval(condition) || !condition){
el.find('li.ui-select-choices-group').append(template);
el.find('ul.ui-select-choices').removeAttr('ng-show');
//watch and
//remove ng-hide class to display this custom item even if there are no more items
scope.$watch(function(){
return el.find('ul.ui-select-choices').hasClass('ng-hide');
},function(newVal){
if(newVal){
$timeout(function() {
el.find('ul.ui-select-choices').removeClass('ng-hide');
});
}
});
el.find('div.custom-option-container button').bind('click',function(){
scope[func].apply(null,[type]);
})
};
}
};
})
HTML：
<ui-select ng-model="asset.category" custom-option='{"buttonText": "Add New Category","click" : "showAddModal","type": "category"}'>
<ui-select-match>{{ $select.selected.categoryName }}
</ui-select-match>
<ui-select-choices repeat="category in categories | filter: $select.search">
<span ng-bind-html="category.categoryName | highlight: $select.search"></span>
</ui-select-choices>
</ui-select>
