Recursion in Angular directives
There are a couple of popular recursive angular directive Q&A's out there, which all come down to one of the following solutions:
The first one has the problem that you can't remove previously compiled code unless you comprehensibly manage the manual compile process. The second approach has the problem of... not being a directive and missing out on its powerful capabilities, but more urgently, it can't be parameterised the same way a directive can be; it's simply bound to a new controller instance.
I've been playing with manually doing an angular.bootstrap or @compile() in the link function, but that leaves me with the problem of manually keeping track of elements to remove and add.
Is there a good way to have a parameterized recursive pattern that manages adding/removing elements to reflect runtime state? That is to say, a tree with a add/delete node button and some input field whose value is passed down a node's child nodes. Perhaps a combination of the second approach with chained scopes (but I have no idea how to do this)?
Inspired by the solutions described in the thread mentioned by @dnc253, I abstracted the recursion functionality into a service.
module.factory('RecursionHelper', ['$compile', function($compile){
return {
/**
* Manually compiles the element, fixing the recursion loop.
* @param element
* @param [link] A post-link function, or an object with function(s) registered via pre and post properties.
* @returns An object containing the linking functions.
*/
compile: function(element, link){
// Normalize the link parameter
if(angular.isFunction(link)){
link = { post: link };
}
// Break the recursion loop by removing the contents
var contents = element.contents().remove();
var compiledContents;
return {
pre: (link && link.pre) ? link.pre : null,
/**
* Compiles and re-adds the contents
*/
post: function(scope, element){
// Compile the contents
if(!compiledContents){
compiledContents = $compile(contents);
}
// Re-add the compiled contents to the element
compiledContents(scope, function(clone){
element.append(clone);
});
// Call the post-linking function, if any
if(link && link.post){
link.post.apply(null, arguments);
}
}
};
}
};
}]);
Which is used as follows:
module.directive("tree", ["RecursionHelper", function(RecursionHelper) {
return {
restrict: "E",
scope: {family: '='},
template:
'<p>{{ family.name }}</p>'+
'<ul>' +
'<li ng-repeat="child in family.children">' +
'<tree family="child"></tree>' +
'</li>' +
'</ul>',
compile: function(element) {
// Use the compile function from the RecursionHelper,
// And return the linking function(s) which it returns
return RecursionHelper.compile(element);
}
};
}]);
See this Plunker for a demo. I like this solution best because:
Manually adding elements and compiling them is definitely a perfect approach. If you use ng-repeat then you will not have to manually remove elements.
Demo: http://jsfiddle.net/KNM4q/113/
.directive('tree', function ($compile) {
return {
restrict: 'E',
terminal: true,
scope: { val: '=', parentData:'=' },
link: function (scope, element, attrs) {
var template = '<span>{{val.text}}</span>';
template += '<button ng-click="deleteMe()" ng-show="val.text">delete</button>';
if (angular.isArray(scope.val.items)) {
template += '<ul class="indent"><li ng-repeat="item in val.items"><tree val="item" parent-data="val.items"></tree></li></ul>';
}
scope.deleteMe = function(index) {
if(scope.parentData) {
var itemIndex = scope.parentData.indexOf(scope.val);
scope.parentData.splice(itemIndex,1);
}
scope.val = {};
};
var newElement = angular.element(template);
$compile(newElement)(scope);
element.replaceWith(newElement);
}
}
});
I don't know for sure if this solution is found in one of the examples you linked or the same basic concept, but I had a need of a recursive directive, and I found a great, easy solution.
module.directive("recursive", function($compile) {
return {
restrict: "EACM",
priority: 100000,
compile: function(tElement, tAttr) {
var contents = tElement.contents().remove();
var compiledContents;
return function(scope, iElement, iAttr) {
if(!compiledContents) {
compiledContents = $compile(contents);
}
iElement.append(
compiledContents(scope,
function(clone) {
return clone; }));
};
}
};
});
module.directive("tree", function() {
return {
scope: {tree: '='},
template: '<p>{{ tree.text }}</p><ul><li ng-repeat="child in tree.children"><recursive><span tree="child"></span></recursive></li></ul>',
compile: function() {
return function() {
}
}
};
});
You should create the recursive directive and then wrap it around the element that makes the recursive call.
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