自定义过滤器让＆QUOT;无法读取不确定＆QUOT财产'片';在AngularJS [英] Custom filter giving "Cannot read property 'slice' of undefined" in AngularJS

问题描述

我的自定义 startFrom 过滤器是给我一个错误。

  app.filter（'startFrom'，函数（）{
    返回功能（输入，启动）{
        开始= +启动; //解析为int
        返回input.slice（开始）;
    }
}）;app.controller（PostCtrl功能（$范围，$ HTTP）{
$ scope.currentPage = 0;
$ scope.pageSize = 10;
$ scope.hidePagination =真;$ scope.search =功能（）{
    $ http.get（'someurl'），然后（sucesscalback，errorcalback）。
    功能sucesscalback（响应）
    {
        $ scope.hidePagination = FALSE;
        的console.log（成功）;
        的console.log（response.data.records）;
        $ scope.posts = response.data;
        $ scope.numberOfPages = Math.ceil（$ scope.posts.records.length / $ scope.pageSize）;
        警报（$ scope.numberOfPages）;
    }
    功能errorcalback（失败）
    {
        的console.log（错误：）;
        的console.log（失败）;
    }
 

解决方案

您过滤器需要检查输入是否存在：

  app.filter（'startFrom'，函数（）{
    返回功能（输入，启动）{
        如果（！输入|| input.length）{返回; }
        开始= +启动; //解析为int
        返回input.slice（开始）;
    }
}）;
 

否则，过滤功能将运行，因此称之为片在未定义不具有的属性片像数组或字符串一样。

虽然没有值过滤器被称为究其原因是因为当角运行其第一个 $消化循环过滤器将运行。您可以通过在控制器中添加一个初始值，避免错误，但最好只到如果语句添加到过滤器。

这里有两种解决方案的演示。注意没有错误。

My custom startFrom filter is giving me an error.

app.filter('startFrom', function() {
    return function(input, start) {
        start = +start; //parse to int
        return input.slice(start);
    }
});

app.controller("PostCtrl", function($scope, $http) {
$scope.currentPage = 0;
$scope.pageSize = 10;
$scope.hidePagination = true;

$scope.search = function() {
    $http.get('someurl').then(sucesscalback,errorcalback);
    function sucesscalback(response)
    {
        $scope.hidePagination = false;
        console.log("Success:");
        console.log(response.data.records);
        $scope.posts = response.data;
        $scope.numberOfPages=Math.ceil($scope.posts.records.length/$scope.pageSize); 
        alert($scope.numberOfPages);
    }
    function errorcalback(failure)
    {
        console.log("Error:");
        console.log(failure);
    }

解决方案

Your filter needs to check whether or not the input exists:

app.filter('startFrom', function() {
    return function(input, start) {
        if (!input || !input.length) { return; }
        start = +start; //parse to int
        return input.slice(start);
    }
});

Otherwise, the filter function will run and thus call slice on undefined which doesn't have a property of slice like an array or string does.

The reason the filter is called while there is no value is because the filter will run when Angular runs its first $digest cycle. You could avoid the error by adding an initial value in the controller, but it's best just to add the if statement to the filter.

Here's a demo of both solutions. Notice there are no errors.

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