angularJs TypeError：将圆形结构转换为 JSON
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angularJs TypeError: Converting circular structure to JSON
提问by Darwin Tech
I have a small AngularJs app like so:
我有一个像这样的小型 AngularJs 应用程序：
// html
<div ng-repeat="project in projects">
<h3>{{ project.id }}</h3>
<h3>{{ project.title }}</h3>
<div ng-repeat="task in project.tasks">
<h4>{{ task.id }}. {{ task.title }}</h4>
<button class="btn btn-default" ng-click="showEditTask=true">Edit Task</button>
<div class="box row animate-show-hide" ng-show="showEditTask">
<h2>Create a New Task</h2>
<form name="newTaskForm" class="form-horizontal">
Title: <br />
<input ng-model="new_task.title" type="text" id="title" name="title" class="form-control" placeholder="Title" required /><br />
Project: <br />
<select ng-model="new_task.project" ng-options="project.title for project in projects" class="form-control"></select><br>
</form>
<button class="btn btn-success" ng-click="createTask(new_task)" ng-disabled="!newTaskForm.title.$valid">create</button>
</div>
</div>
</div>
// app.js
concernsApp.factory('ConcernService', function ($http, $q) {
...
update: function (obj_url, obj) {
var defer = $q.defer();
console.log(obj)
$http({method: 'POST',
url: api_url + obj_url + obj.id + '/',
data: obj}).
success(function (data, status, headers, config) {
defer.resolve(data);
}).error(function (data, status, headers, config) {
defer.reject(status);
});
return defer.promise;
},
});
concernsApp.controller('ProjectsCtrl', function ($scope, $http, ConcernService) {
$scope.updateTask = function(obj) {
ConcernService.update('tasks/', obj).then(function(){
...
}
});
The problem is with updating a task and leaving the parent project as is. If I change the parent project, it all works fine. If I use the same parent project then I get:
问题在于更新任务并按原样保留父项目。如果我更改父项目，一切正常。如果我使用相同的父项目，那么我会得到：
TypeError: Converting circular structure to JSON
I'm not entirely sure what is happening here.
我不完全确定这里发生了什么。
Edit
编辑
So, I can solve the problem like this:
所以，我可以解决这样的问题：
$scope.updateTask = function(obj) {
parentProject = {'id': obj.project.id};
obj.project = parentProject;
ConcernService.update('tasks/', obj).then(function(){
...
});
};
This works as I only actually need the task.project.idto update the object. I thinkthe problem is due to that fact that the task references a parent project, which in turn references the child tasks etc. I'm not entirely sure about this tough.
这有效，因为我实际上只需要task.project.id更新对象。我认为问题是由于该任务引用了一个父项目，而该父项目又引用了子任务等。我不完全确定这很难。
However, this solution seems a little hacky to me and I would love to see a better solution.
但是，这个解决方案对我来说似乎有点棘手，我很想看到更好的解决方案。
回答by bgse
Somewhere you are trying to convert an object to JSON, and that has a circular reference in it, meaning something like this:
在某个地方，您尝试将对象转换为 JSON，并且其中有一个循环引用，意思是这样的：
var myObj = new Object();
myObject.reference = myObj;
Now trying to convert this to JSON will fail, and produce your error.
现在尝试将其转换为 JSON 将失败，并产生您的错误。
Looking at the your edited post, your data structure is something like this:
看看你编辑过的帖子，你的数据结构是这样的：
task.parent -> {project}
project.tasks -> [{task1},{task2},...]
This is supposed to model the relation "project has multiple tasks" and "task belongs to a project".
这应该模拟“项目有多个任务”和“任务属于一个项目”的关系。
Now this can obviously not be converted to json format, due to circular referencing.
由于循环引用，现在这显然不能转换为json格式。
For the data structure, why not go with:
对于数据结构，为什么不使用：
project = { "id": 42,
"tasks": [123, 124, 127, ... ],
}
task = { "id": 123,
"idproject": 42,
...
}
Whenever you have to show the relationships in your angularjs app, you could go with filters. If you want to show what belongs to a project, filter all tasks by projectid.
每当您必须在 angularjs 应用程序中显示关系时，您都可以使用过滤器。如果要显示属于某个项目的内容，请按 projectid 过滤所有任务。
Or retrieve only the required data from your backend on the fly, by requesting what tasks the backend has for a specific project id.
或者通过请求后端针对特定项目 ID 的任务，仅从后端动态检索所需数据。
That is one way to do it. Of course, having the backend accept appropriate update requests would be working just as well, e.g. updating a project would require the project id, and an array of task ids.
这是一种方法。当然，让后端接受适当的更新请求也能正常工作，例如更新项目需要项目 ID 和任务 ID 数组。
