Angularjs:理解递归指令

Ng 网站有一些很棒的文档(在我看来是最好的(。 启动和运行时循环的概述非常有用：http://docs.angularjs.org/guide/concepts

在高层次上，当 Ng 第一次启动时，它会从 ng-app 所在的位置开始编译 DOM(就像 Ng 的另一个指令一样(。 这意味着它遍历元素并查看链接到$rootScope(编译/链接过程设置的原型继承链的一部分的所有范围的根(所需的指令和表达式。 如果它是一个指令，编译过程也会在其上完成。 编译过程获取它在 HTML 中找到的所有 Ng 指令，并根据分配的优先级或假设优先级为零来确定它们的优先级。 当它们都排序时，它会执行返回链接函数的指令的编译函数。 在上面的例子中，有两个显示链接函数，我将在下面注释它们，以及将其链接到此解释的其他注释。 链接函数还以 transclude 对象的形式为该指令作为属性、类或元素的元素中的 HTML 提供 HTML。

，该函数链接范围和指令以及生成视图。 这可能包括 HTML/transclude，因此可以在指令 ng-transclude 位于指令模板中的位置添加它(它将应用相同的过程，其模板是 transclude(。

因此，以下是我对上面略微更正的自定义指令的注释：

module.directive("tree", function($compile) {
    //Here is the Directive Definition Object being returned 
    //which is one of the two options for creating a custom directive
    //http://docs.angularjs.org/guide/directive
    return {
        restrict: "E",
        //We are stating here the HTML in the element the directive is applied to is going to be given to
        //the template with a ng-transclude directive to be compiled when processing the directive
        transclude: true,
        scope: {family: '='},
        template:       
            '<ul>' + 
                //Here we have one of the ng-transclude directives that will be give the HTML in the 
                //element the directive is applied to
                '<li ng-transclude></li>' +
                '<li ng-repeat="child in family.children">' +
                    //Here is another ng-transclude directive which will be given the same transclude HTML as
                    //above instance
                    //Notice that there is also another directive, 'tree', which is same type of directive this 
                    //template belongs to.  So the directive in the template will handle the ng-transclude 
                    //applied to the div as the transclude for the recursive compile call to the tree 
                    //directive.  The recursion will end when the ng-repeat above has no children to 
                    //walkthrough.  In other words, when we hit a leaf.
                    '<tree family="child"><div ng-transclude></div></tree>' +
                '</li>' +
            '</ul>',
        compile: function(tElement, tAttr, transclude) {
            //We are removing the contents/innerHTML from the element we are going to be applying the 
            //directive to and saving it to adding it below to the $compile call as the template
            var contents = tElement.contents().remove();
            var compiledContents;
            return function(scope, iElement, iAttr) {
                if(!compiledContents) {
                    //Get the link function with the contents frome top level template with 
                    //the transclude
                    compiledContents = $compile(contents, transclude);
                }
                //Call the link function to link the given scope and
                //a Clone Attach Function, http://docs.angularjs.org/api/ng.$compile :
                // "Calling the linking function returns the element of the template. 
                //    It is either the original element passed in, 
                //    or the clone of the element if the cloneAttachFn is provided."
                compiledContents(scope, function(clone, scope) {
                        //Appending the cloned template to the instance element, "iElement", 
                        //on which the directive is to used.
                         iElement.append(clone); 
                });
            };
        }
    };
});

整个工作：http://jsfiddle.net/DsvX6/7/