带有默认选项的 AngularJS 指令 [英] AngularJS directive with default options

问题描述

我刚刚开始使用 angularjs，并且正在将一些旧的 JQuery 插件转换为 Angular 指令.我想为我的(元素)指令定义一组默认选项，可以通过在属性中指定选项值来覆盖这些选项.

I'm just starting with angularjs, and am working on converting a few old JQuery plugins to Angular directives. I'd like to define a set of default options for my (element) directive, which can be overridden by specifying the option value in an attribute.

我查看了其他人的做法，在 angular-ui 库中，ui.bootstrap.pagination 似乎做了类似的事情.

I've had a look around for the way others have done this, and in the angular-ui library the ui.bootstrap.pagination seems to do something similar.

首先在一个常量对象中定义所有默认选项:

First all default options are defined in a constant object:

.constant('paginationConfig', {
  itemsPerPage: 10,
  boundaryLinks: false,
  ...
})

然后一个 getAttributeValue 实用函数被附加到指令控制器:

Then a getAttributeValue utility function is attached to the directive controller:

this.getAttributeValue = function(attribute, defaultValue, interpolate) {
    return (angular.isDefined(attribute) ?
            (interpolate ? $interpolate(attribute)($scope.$parent) :
                           $scope.$parent.$eval(attribute)) : defaultValue);
};

最后，这在链接函数中用于读取属性

Finally, this is used in the linking function to read in attributes as

.directive('pagination', ['$parse', 'paginationConfig', function($parse, config) {
    ...
    controller: 'PaginationController',
    link: function(scope, element, attrs, paginationCtrl) {
        var boundaryLinks = paginationCtrl.getAttributeValue(attrs.boundaryLinks,  config.boundaryLinks);
        var firstText = paginationCtrl.getAttributeValue(attrs.firstText, config.firstText, true);
        ...
    }
});

对于像想要替换一组默认值这样的标准设置，这似乎是一个相当复杂的设置.有没有其他常见的方法可以做到这一点?或者总是这样定义一个实用函数比如getAttributeValue并解析选项是正常的吗?我很想知道人们对这项常见任务有哪些不同的策略.

This seems like a rather complicated setup for something as standard as wanting to replace a set of default values. Are there any other ways to do this that are common? Or is it normal to always define a utility function such as getAttributeValue and parse options in this way? I'm interested to find out what different strategies people have for this common task.

另外，作为奖励，我不清楚为什么需要 interpolate 参数.

Also, as a bonus, I'm not clear why the interpolate parameter is required.

推荐答案

您可以使用 compile 功能 - 如果未设置属性，则读取它们 - 使用默认值填充它们.

You can use compile function - read attributes if they are not set - fill them with default values.

.directive('pagination', ['$parse', 'paginationConfig', function($parse, config) {
    ...
    controller: 'PaginationController',
    compile: function(element, attrs){
       if (!attrs.attrOne) { attrs.attrOne = 'default value'; }
       if (!attrs.attrTwo) { attrs.attrTwo = 42; }
    },
        ...
  }
});

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