我正在尝试根据所选类别过滤某些频道.
我在通道中有一个ng-repeat的通道,它有一个ng-if =“hasCategory(channel.category)
这是文件：
db.channels.find().pretty()
{
"_id" : "2kj9GK8jE9yHezoWb","name" : "example name","logo" : "path/to/image.svg","number" : 2,"category" : [
"Broadcast","Premium"
],"tags" : "example tag tags"
}
这是处理ng-if的函数：
$scope.hasCategory = function (categoryNameArray) {
console.log('thisisbeingcalled');
var e = _.indexOf(categoryNameArray,$scope.activeCategory);
if (e === -1) {
return false;
} else {
return true;
}
};
这就是我设置活动类别的方式：
$scope.setCategory = function (name) {
$scope.activeCategory = name;
};
我通过单击视图中的按钮发送：
<section layout="row" layout-align="center center" layout-wrap ng-init="activeIndex; activeCategory">
<md-button flex="auto" flex-sm="45" flex-xs="100" ng-repeat="kit in kits | orderBy: 'order'" ng-class="{active: (activeIndex.index == $index)}" class="md-raised">
<a href="" ng-click="activeIndex.index = $index; setCategory(kit.name);" class="bold">{{kit.name}}</a>
</md-button>
</section>
这是套件文档架构：
db.kits.find().pretty()
{ "_id" : "k7JFX6DHu5GYnyer3","name" : "Broadcast","order" : 1 }
{ "_id" : "KrKRm4gysw5sfQnnr","name" : "Premium","order" : 2 }
{ "_id" : "dieukQ3NRsA44CSns","name" : "Ultimate","order" : 3 }
现在我只有一个通道来测试它,但每次单击按钮更改类别时,$scope.hasCategory函数即使在页面启动时也会被多次调用(第一次加载)
我还有一个搜索栏来搜索当前类别中的频道,我不确定这是否会影响到这一点.
<input type="text" ng-model="queryname" ng-model-options="{debounce: 500}">
现在,当我有超过100个通道时,这会变得非常滞后,ng-if被调用超过10k次,这使得页面冻结了很长一段时间.
我该怎么做才能解决这个问题？
编辑
忘了添加ng-if的位置：
<md-card flex="15" flex-xs="40" class="slide-up" layout="column" ng-repeat="channel in channels | orderBy: 'number' | filter: queryname" ng-if="hasCategory(channel.category)" ng-init="channel.edit = false">
<md-card-header ng-show="channel.edit == false">
<img ng-src="{{channel.logo}}" alt="">
</md-card-header>
<md-card-header-text ng-show="channel.edit == false">
<span class="md-subhead dark-blue" layout="row" layout-align="center" layout-margin>{{channel.number}}</span>
</md-card-header-text>
</md-card>
解决方法
每个摘要循环都会调用你的ng-if.问题是它包含一个涉及函数调用的表达式. Angular无法知道表达式的结果何时可能发生变化,因此每次都会调用它.
更好的选择是在每个通道中设置一个标志,并使用ng-if来测试相关标志.然后,只要$scope.activeCategory更改,您就可以更新标记,您可以使用代码设置类别或使用$scope.$watch()自动触发它.
例如
$scope.setCategory = function (name) {
$scope.activeCategory = name;
for (var index=0; index < $scope.channels.length; index++) {
$scope.channels[index].hasCategory = hasCategory($scope.channels[index].category,name);
}
};
function hasCategory(categoryNameArray,name) {
console.log('thisisbeingcalled');
var e = _.indexOf(categoryNameArray,name);
if (e === -1) {
return false;
} else {
return true;
}
}
然后在你的模板中：
<md-card flex="15" flex-xs="40" class="slide-up" layout="column"
ng-repeat="channel in channels | orderBy: 'number' | filter: queryname"
ng-if="channel.hasCategory"
ng-init="channel.edit = false">
<md-card-header ng-show="channel.edit == false">
<img ng-src="{{channel.logo}}" alt="">
</md-card-header>
<md-card-header-text ng-show="channel.edit == false">
<span class="md-subhead dark-blue" layout="row" layout-align="center" layout-margin>{{channel.number}}</span>
</md-card-header-text>
</md-card>
应该更有效率.
