Question

我刚开始学习AngularJS，我看到了一个教程，给出了以下示例：

;With Cte_1(ID,ProductCode,[Date],PurchQty,CurrentStock)
As
(
SELECT 1001,'AB101','14/12/2016',  9,14 Union All
SELECT 1111,'AB101','01/01/2017', 18,14 Union All
SELECT 1223,'AB101','15/01/2017', 20,14 Union All
SELECT 1233,'BB400','02/01/2017', 50,40 Union All
SELECT 1321,'AB101','31/01/2017',  8,14 Union All
SELECT 1400,'BB400','12/12/2016', 90,40 Union All
SELECT 1456,'CC200','13/03/2017',100,20
),
cte2 AS (
        SELECT ProductCode
            ,[Date]
            ,CASE 
                WHEN Sum(PurchQty) OVER (
                        PARTITION BY ProductCode
                        ,[DATE] ORDER BY ProductCode
                        ) >= CurrentStock
                    THEN PurchQty
                END SumPurchQty
            ,CurrentStock
        FROM Cte_1
        )
    ,Cte3 AS (
        SELECT ROW_NUMBER() OVER (
                PARTITION BY ProductCode ORDER BY SumPurchQty DESC
                ) AS SeqOrder
            ,ProductCode,[DATE],SumPurchQty,CurrentStock
        FROM cte2
        )

SELECT ProductCode
    ,[Date]
    ,SumPurchQty
    ,CurrentStock
FROM Cte3
WHERE SeqOrder = 1

我想知道 - 为什么函数需要嵌套？为什么我不能写这个：

<!DOCTYPE html>
<html>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular.min.js"></script>
<body>

<ul ng-app="myApp" ng-controller="namesCtrl">
<li ng-repeat="x in names">
    {{x | myFormat}}
</li>
</ul>

<script>
var app = angular.module('myApp', []);
app.filter('myFormat', function() {
    return function(x) {
        var i, c, txt = "";
        for (i = 0; i < x.length; i++) {
            c = x[i];
            if (i % 2 == 0) {
                c = c.toUpperCase();
            }
            txt += c;
        }
        return txt;
    };
});
app.controller('namesCtrl', function($scope) {
    $scope.names = [
        'Jani',
        'Carl',
        'Margareth',
        'Hege',
        'Joe',
        'Gustav',
        'Birgit',
        'Mary',
        'Kai'
        ];
});
</script>

<p>Make your own filters.</p>
<p>This filter, called "myFormat", will uppercase every other character.</p>
</body>
</html>

还有一个问题 - 哪个\谁将x传递给函数？我知道大部分时间我都会将数据传递到这样的结果 - var app = angular.module('myApp', []); app.filter('myFormat', function(x) { var i, c, txt = ""; for (i = 0; i < x.length; i++) { c = x[i]; if (i % 2 == 0) { c = c.toUpperCase(); } txt += c; } return txt; }); - 这里在哪里？

谢谢！

Answer 1

这是设计。 filter API具有返回function（过滤逻辑）的函数。基本上可以利用外部来利用角度依赖性。并且在每个摘要周期中评估内部返回函数。

//sample filter
app.filter('upperCase',[ '$window', function($window){ //you could have dependency here
   //inner function
   return function(x){
      return x.toUpperCase();
   }
}]);

上面x是应用过滤器的值。在您的情况下{{x | myFormat}}该参数将是x变量范围值。每当您想要在过滤器中传递多个参数时，您可以在过滤器名称由:

分隔后立即提及更多值

{{x | myFormat: y: z}}

为什么角函数需要嵌套？

1 个答案: