AngularJS: 理解递归指令

Question

AngularJS: 理解递归指令

javascriptangularjs

15

我在这里找到了一个很棒的树形指令。原链接：http://jsfiddle.net/n8dPm/

我通过查看其他几篇SO问题（1，2）尝试理解它的工作原理。但我并没有很清楚地理解递归调用渲染树形指令的方式，主要是compile函数。

compile函数什么时候被全部调用？
什么时候将$compile函数缓存到变量compiledContents中（这是link函数吗？），什么时候将它附加到HTML文档中？为什么不总是附加？

--

compile: function(tElement, tAttr) {
            var contents = tElement.contents().remove();
            var compiledContents;
            return function(scope, iElement, iAttr) {
                if(!compiledContents) {
                    compiledContents = $compile(contents);
                }
                compiledContents(scope, function(clone, scope) {
                         iElement.append(clone); 
                });
            };
        },

- bsr

1个回答

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Erstad.Stephen · Accepted Answer

Ng网站拥有非常优秀的文档（在我看来是最好的之一）。其中关于启动和运行循环的概述非常有帮助：http://docs.angularjs.org/guide/concepts

从高层次上讲，当Ng首次启动时，它会编译DOM，从ng-app所在位置开始（被Ng视为另一个指令）。这意味着它会遍历元素并查找需要链接到$rootScope（由编译/链接过程设置的原型继承链中所有作用域的根）的指令和表达式。如果是指令，则也对其进行编译处理。编译处理将所有在HTML中发现的Ng指令按其分配的优先级排序或假定优先级为零。当它已经将它们全部排序后，就会执行指令的编译函数，该函数返回链接函数。在上面的示例中，有两个show链接函数，我将在下面进行注释，并将其与此解释相关联。链接函数还以传输对象的形式获得了指令所在属性、类或元素中的HTML。

执行链接函数以链接作用域和指令，同时生成视图。这可能包括HTML/传输对象，以便在指令ng-transclude处添加（该模板将应用相同的过程，其模板是传输对象）。

因此，这里是我对以上略作纠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); 
                });
            };
        }
    };
});

整个事情正在运作中：http://jsfiddle.net/DsvX6/7/