解析来自 JSON 对象的循环引用 [英] Resolve circular references from JSON object

问题描述

如果我有一个来自 json.net 的序列化 JSON，就像这样:

If I have a serialized JSON from json.net like so:

User:{id:1,{Foo{id:1,prop:1}},
FooList{$ref: "1",Foo{id:2,prop:13}}

我想在 FooList 上输出一个 foreach，但我不知道如何继续，因为 $ref 的东西可能会抛出东西.

I want to have knockout output a foreach over FooList but I am not sure how to proceed because the $ref things could throw things.

我认为解决方案是通过不使用以某种方式强制所有 Foo 在 FooList 中呈现:

I'm thinking the solution would be to somehow force all the Foos to be rendered in the FooList by not using:

PreserveReferencesHandling = PreserveReferencesHandling.Objects

但这似乎很浪费..

推荐答案

您从服务器接收的 json 对象包含 循环引用.在使用对象之前，您应该首先从对象中删除所有 $ref 属性，这意味着代替 $ref : "1" 您必须将对象放在这个链接点.

The json object which you are receiving from the server contains Circular References. Before using the object you should have to first remove all the $ref properties from the object, means in place of $ref : "1" you have to put the object which this link points.

在您的情况下，它可能指向 id 为 1 的用户对象

为此，您应该查看 github 上的 Douglas Crockfords 插件.有一个 cycle.js 可以完成这项工作给你.

For this you should check out Douglas Crockfords Plugin on github.There is a cycle.js which can do the job for you.

或者您可以使用以下代码(未测试):

or you can use the following code (not tested) :

function resolveReferences(json) {
    if (typeof json === 'string')
        json = JSON.parse(json);

    var byid = {}, // all objects by id
        refs = []; // references to objects that could not be resolved
    json = (function recurse(obj, prop, parent) {
        if (typeof obj !== 'object' || !obj) // a primitive value
            return obj;
        if ("$ref" in obj) { // a reference
            var ref = obj.$ref;
            if (ref in byid)
                return byid[ref];
            // else we have to make it lazy:
            refs.push([parent, prop, ref]);
            return;
        } else if ("$id" in obj) {
            var id = obj.$id;
            delete obj.$id;
            if ("$values" in obj) // an array
                obj = obj.$values.map(recurse);
            else // a plain object
                for (var prop in obj)
                    obj[prop] = recurse(obj[prop], prop, obj)
            byid[id] = obj;
        }
        return obj;
    })(json); // run it!

    for (var i=0; i<refs.length; i++) { // resolve previously unknown references
        var ref = refs[i];
        ref[0][ref[1]] = byid[refs[2]];
        // Notice that this throws if you put in a reference at top-level
    }
    return json;
}  

如果有帮助，请告诉我！

Let me know if it helps !

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