Someone may well point to a duplicate on this. But I have searched. There are lots of questions on the subject, but none I've really seems to help.
The structure of my delivered JSON (from Elasticsearch) is like this:
When I go:
let json_hashmap: HashMap<String, Value> = serde_json::from_str(&text).unwrap();
I get this:
{
"hits": Object {
"hits": Array [
Object {
"_id": String("Ybgt6ooBpXznUptX4lR2"),
"_index": String("booby"),
"_score": Number(1.0),
... (other keys)
],
... (multiple other hit-hit Objects in the Array)
],
... (other keys)
}
"key2": String("my arbitrary string value"),
"key3": Number(1.0),
... (other keys)
}
It's not that the keys and nested array of hit-hit "dictionaries" are unpredictable. I can devise a struct for these hit-hit dictionaries. But how can I actually obtain the array of hit-hits?
Because as can be seen, the level 0 dictionary (outer dictionary) has ONE key which decodes to an inner dictionary ("level 1") containing an array of inner-inner dictionaries ("level 2").
But the level 0 dictionary has keys other than "hits" which decode to other values. And indeed the level 1 dictionary may also have keys other than "hits".
Is there a way of stipulating that one particular key in the "level 0" (outer) dictionary decodes to HashMap<String, Value> and that one particular key in that dictionary decodes to Vec<MyStruct>?
NB I can get access to some object if I go
let outer_hits = &json_hasmap["hits"];
let inner_hits = &outer_hits["hits"];
Printing this using {:#?} shows this:
Array [
Object {
"_id": String("Ybgt6ooBpXznUptX4lR2"),
"_index": String("booby"),
"_score": Number(1.0),
"_source": Object {
"docx_id": Number(14),
"last_modif_ms": Number(1596958203000),
"ldoc_type": String("docx_doc"),
"path": String("D:\\My Documents\\doc\\IT_Diary\\IT Diary $UPD 2018-03.docx"),
},
},
Object {
...
... but, for example, although this is said to be type Array, my attempt to go inner_hits.len() won't compile: I get " ^^^ method not found in &Value". Strange kind of an "array". How can I extract something more useable?
text at the very start is:
{
"_scroll_id": "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",
"took": 3,
"timed_out": false,
"_shards": {
"total": 10,
"successful": 10,
"skipped": 3,
"failed": 0
},
"hits": {
"total": {
"value": 5303,
"relation": "eq"
},
"max_score": 1,
"hits": [
{
"_index": "booby",
"_id": "Ybgt6ooBpXznUptX4lR2",
"_score": 1,
"_source": {
"docx_id": 14,
"last_modif_ms": 1596958203000,
"ldoc_type": "docx_doc",
"path": "D:\\My Documents\\doc\\IT_Diary\\IT Diary $UPD 2018-03.docx"
}
},
{
"_index": "booby",
"_id": "jLgt6ooBpXznUptX4lSG",
"_score": 1,
"_source": {
"docx_id": 12,
"last_modif_ms": 1596958248000,
"ldoc_type": "docx_doc",
"path": "D:\\My Documents\\doc\\IT_Diary\\IT Diary $UPD 2018-01.docx"
}
},
{
"_index": "booby",
"_id": "1bgt6ooBpXznUptX4lSX",
"_score": 1,
"_source": {
"docx_id": 20,
"last_modif_ms": 1596958053000,
"ldoc_type": "docx_doc",
"path": "D:\\My Documents\\doc\\IT_Diary\\IT Diary $UPD 2018-09.docx"
}
},
{
"_index": "booby",
"_id": "7rgt6ooBpXznUptX4lSm",
"_score": 1,
"_source": {
"docx_id": 21,
"last_modif_ms": 1596958032000,
"ldoc_type": "docx_doc",
"path": "D:\\My Documents\\doc\\IT_Diary\\IT Diary $UPD 2018-10.docx"
}
},
{
"_index": "booby",
"_id": "_rgt6ooBpXznUptX4lS2",
"_score": 1,
"_source": {
"docx_id": 22,
"last_modif_ms": 1596957990000,
"ldoc_type": "docx_doc",
"path": "D:\\My Documents\\doc\\IT_Diary\\IT Diary $UPD 2018-11.docx"
}
}
]
}
}
It is best to model your own types that reflect the expected JSON structure instead of using a generic Value. You can do that by implementing serde::Deserialize. Something like this (only some fields implemented):
use serde::Deserialize;
use serde_json::json;
#[derive(Debug, Deserialize)]
struct Response {
// _scroll_id
// took
// timed_out
// _shards
hits: HitsResponse,
}
#[derive(Debug, Deserialize)]
struct HitsResponse {
// total
// max_score
hits: Vec<Hit>,
}
#[derive(Debug, Deserialize)]
struct Hit {
// _index
_id: String,
// _score
_source: HitSource,
}
#[derive(Debug, Deserialize)]
struct HitSource {
// docx_id
// last_modif_ms,
// ldoc_type
path: String,
}
Parsing your JSON into a Response above would yield this:
let response: Response = serde_json::from_str(&text).unwrap();
Response {
hits: HitsResponse {
hits: [
Hit {
_id: "Ybgt6ooBpXznUptX4lR2",
_source: HitSource {
path: "D:\\My Documents\\doc\\IT_Diary\\IT Diary $UPD 2018-03.docx",
},
},
Hit {
_id: "jLgt6ooBpXznUptX4lSG",
_source: HitSource {
path: "D:\\My Documents\\doc\\IT_Diary\\IT Diary $UPD 2018-01.docx",
},
},
Hit {
_id: "1bgt6ooBpXznUptX4lSX",
_source: HitSource {
path: "D:\\My Documents\\doc\\IT_Diary\\IT Diary $UPD 2018-09.docx",
},
},
Hit {
_id: "7rgt6ooBpXznUptX4lSm",
_source: HitSource {
path: "D:\\My Documents\\doc\\IT_Diary\\IT Diary $UPD 2018-10.docx",
},
},
Hit {
_id: "_rgt6ooBpXznUptX4lS2",
_source: HitSource {
path: "D:\\My Documents\\doc\\IT_Diary\\IT Diary $UPD 2018-11.docx",
},
},
],
},
}
And if you're using reqwest, you can use .json directly instead of .text or .bytes + serde_json (by enabling its "json" feature).