如何解组嵌套的未知字段
谷梁宝
问题内容：
问题答案：
我在这里分叉了一个很棒的项目，并且刚刚学习了一些东西，就把它弄乱了。我不知道的问题是有关自定义编组的一些问题，如果您在这里看到，您可以看到它解组了Thing包含一个Data interface{}字段的结构，然后使用该Kind string字段将其解组。除了嵌套的情况，这一切都很好。因此，最好的例子是：
只需说您有Thing一个善意的结构是a
listing，那么就可以将Thing.Data其编组listing。然后listing具有3个保留在字段中Children的类型。这些孩子最终成为我的问题类型。我如何才能解决嵌套数据的问题？这样一来，也就无法编组。有没有办法做到这一点，还是我必须编写一个大循环或递归算法？请让我知道您的想法，或者如果我看待这种情况都错了。谢谢link``Children []Thing``map[string]interface {}``Children.Data
更新 这是一个json示例
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"kind": "Listing",
"data": {
"after": null,
"dist": 10,
"facets": {},
"modhash": null,
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{
"kind": "t3",
"data": {
"domain": "self.nanocurrency",
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"selftext_html": "<!-- SC_OFF --><div class=\"md\"><p>Seeing lots of comments about the lack of timestamps in the protocol, and just wanted to provide some information on why objectively accurate, global time timestamps are an illusion in decentralized systems. Logical time on the other hand is achievable and is in fact achieved in Nano via the individual block chains and the directed, acyclic graph (DAG). </p>\n\n<p>Generally, in a decentralized, distributed system, only logical time (C happened after B happened after A) can be agreed on globally (e.g. Lamport time: <a href=\"https://amturing.acm.org/p558-lamport.pdf\">https://amturing.acm.org/p558-lamport.pdf</a> or vector clocks). This is what the nano ledger does via chaining blocks, just as any other blockchain. Then it connects those chains via a DAG. Syncing global time to logical time is a hard problem that can either be approached via a consensus approach which is prone to sybil attacks, via a probabilistic approach which is what most blockchains go with - essentially relying on their peers - or a centralized approach like NTP which is a no-go in a decentralized system. If you&#39;re interested, check e.g. this paper: <a href=\"http://soft.vub.ac.be/%7Etvcutsem/distsys/clocks.pdf\">http://soft.vub.ac.be/~tvcutsem/distsys/clocks.pdf</a></p>\n\n<p>So what you&#39;re running into is the problem that while theoretically all or a relevant subset of nodes within the Nano or Bitcoin or Ethereum network could agree to call a certain time &quot;Monday February 12 2018 20:35:23&quot;, this timestamp could still be incorrect vs the outside world.</p>\n\n<p>That&#39;s why any accurate global timestamps in software today rely on centralized information and trusted entities. The only way this can change is if machines start setting their clocks on their own accurately (e.g. chip-scale atomic clocks)</p>\n\n<p>Some people think this is bad news for Nano because in traditional blockchain, timestamps are fairly important because they are used in new block validation: <a href=\"http://culubas.blogspot.co.uk/2011/05/timejacking-bitcoin_802.html\">http://culubas.blogspot.co.uk/2011/05/timejacking-bitcoin_802.html</a> . Timestamps are a blessing and a curse at the same time in blockchain: They allow for timing and validation of blocks and therefore regulation of coin mining, but also allow for timestamp double spend attacks. Since Nano does not use mining, it is not susceptible to those attacks.</p>\n\n<p>Even with the relative importance of time and timestamps in Bitcoin, timestamp in Bitcoin are not guaranteed to be corresponding to logical time on the chain. Here&#39;s the bitcoin wiki talking about the bitcoin block timestamp: <a href=\"https://en.bitcoin.it/wiki/Block_timestamp\">https://en.bitcoin.it/wiki/Block_timestamp</a> </p>\n\n<blockquote>\n<p>A timestamp is accepted as valid if it is greater than the median timestamp of previous 11 blocks, and less than the network-adjusted time + 2 hours. &quot;Network-adjusted time&quot; is the median of the timestamps returned by all nodes connected to you. As a result, block timestamps are not exactly accurate, and they do not even need to be in order. Block times are accurate only to within an hour or two. </p>\n</blockquote>\n\n<p>This is probably as good as it gets. Still no ordering guarantees though, and a possibilities for attacks which have been discussed again and again. There are certain guards in Bitcoin code to prevent these from happening. </p>\n\n<p>So if you have somebody lecturing you about how architecturally superior coins would have a accurate and monotonically increasing timestamps, point them here, or here: <a href=\"https://cointelegraph.com/news/timestamp-hacking-debunking-the-myth-of-precision-timestamps\">https://cointelegraph.com/news/timestamp-hacking-debunking-the-myth-of-precision-timestamps</a></p>\n\n<p>Would timestamps be convenient to have on the protocol? Yes, and that would likely be a good reason to include them. Are timestamps accurately depicting global time, and can they be used as evidence in any chain? No they can&#39;t.</p>\n\n<p>Why are we seeing inaccurate timestamps in the block explorer? Because these are kept in a db outside of the ledger and have been set January 19. Nothing more to it.</p>\n\n<p>Why do people like to babble about how this is a weakness in Nano? No clue.</p>\n</div><!-- SC_ON -->",
"selftext": "Seeing lots of comments about the lack of timestamps in the protocol, and just wanted to provide some information on why objectively accurate, global time timestamps are an illusion in decentralized systems. Logical time on the other hand is achievable and is in fact achieved in Nano via the individual block chains and the directed, acyclic graph (DAG). \n\nGenerally, in a decentralized, distributed system, only logical time (C happened after B happened after A) can be agreed on globally (e.g. Lamport time: https://amturing.acm.org/p558-lamport.pdf or vector clocks). This is what the nano ledger does via chaining blocks, just as any other blockchain. Then it connects those chains via a DAG. Syncing global time to logical time is a hard problem that can either be approached via a consensus approach which is prone to sybil attacks, via a probabilistic approach which is what most blockchains go with - essentially relying on their peers - or a centralized approach like NTP which is a no-go in a decentralized system. If you're interested, check e.g. this paper: http://soft.vub.ac.be/~tvcutsem/distsys/clocks.pdf\n\nSo what you're running into is the problem that while theoretically all or a relevant subset of nodes within the Nano or Bitcoin or Ethereum network could agree to call a certain time \"Monday February 12 2018 20:35:23\", this timestamp could still be incorrect vs the outside world.\n\nThat's why any accurate global timestamps in software today rely on centralized information and trusted entities. The only way this can change is if machines start setting their clocks on their own accurately (e.g. chip-scale atomic clocks)\n\nSome people think this is bad news for Nano because in traditional blockchain, timestamps are fairly important because they are used in new block validation: http://culubas.blogspot.co.uk/2011/05/timejacking-bitcoin_802.html . Timestamps are a blessing and a curse at the same time in blockchain: They allow for timing and validation of blocks and therefore regulation of coin mining, but also allow for timestamp double spend attacks. Since Nano does not use mining, it is not susceptible to those attacks.\n\nEven with the relative importance of time and timestamps in Bitcoin, timestamp in Bitcoin are not guaranteed to be corresponding to logical time on the chain. Here's the bitcoin wiki talking about the bitcoin block timestamp: https://en.bitcoin.it/wiki/Block_timestamp \n\n> A timestamp is accepted as valid if it is greater than the median timestamp of previous 11 blocks, and less than the network-adjusted time + 2 hours. \"Network-adjusted time\" is the median of the timestamps returned by all nodes connected to you. As a result, block timestamps are not exactly accurate, and they do not even need to be in order. Block times are accurate only to within an hour or two. \n\nThis is probably as good as it gets. Still no ordering guarantees though, and a possibilities for attacks which have been discussed again and again. There are certain guards in Bitcoin code to prevent these from happening. \n\nSo if you have somebody lecturing you about how architecturally superior coins would have a accurate and monotonically increasing timestamps, point them here, or here: https://cointelegraph.com/news/timestamp-hacking-debunking-the-myth-of-precision-timestamps\n\nWould timestamps be convenient to have on the protocol? Yes, and that would likely be a good reason to include them. Are timestamps accurately depicting global time, and can they be used as evidence in any chain? No they can't.\n\nWhy are we seeing inaccurate timestamps in the block explorer? Because these are kept in a db outside of the ledger and have been set January 19. Nothing more to it.\n\nWhy do people like to babble about how this is a weakness in Nano? No clue.",
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},
问题答案：
这正是json.RawMessage的目的（请参阅文档中的unmarshal示例）。首先解组JSON对象的顶级，检查kind字段，然后解组数据字段：
type Listing struct {
WhitelistStatus string `json:"whitelist_status"`
Children []Thing `json:"children"`
}
type T3 struct {
Domain string `json:"domain"`
CrosspostParentList []struct {
Domain string `json:"domain"`
} `json:"crosspost_parent_list"`
}
type Thing struct {
Kind string `json:"kind"`
Data interface{} `json:"data"`
}
func (t *Thing) UnmarshalJSON(b []byte) error {
var step1 struct {
Kind string `json:"kind"`
Data json.RawMessage `json:"data"`
}
if err := json.Unmarshal(b, &step1); err != nil {
return err
}
var step2 interface{}
switch step1.Kind {
case "Listing":
step2 = &Listing{}
case "t3":
step2 = &T3{}
default:
return errors.New("unknown kind: " + step1.Kind) // or simply ignore
}
if err := json.Unmarshal(b, step2); err != nil {
return err
}
t.Kind = step1.Kind
t.Data = step2
return nil
}
在操场上尝试：https :
//play.golang.org/p/giBVT2IWPd-
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