JsonParserGeneratorRK - parsing a Child Key from a Firebase GET webhook

Firmware Libraries
1

I have a JSON object from Firebase that I need to parse the Firebase Key. I’ve read through the JsonParserGeneratorRK library information but can’t seem to find which function or an example to use to parse my Key value “-M5sN1MfCHcXHkLBlwWW”

my GET webhook is working, here’s an abbreviated hook-response:

{"-M5sN1MfCHcXHkLBlwWW":{"aug":false,"fan":true,"ign":true}}

and here’s my parser1 code

void getDataHandler(const char *event, const char *data) {
    JsonParserStatic<768, 60> parser1;
    parser1.clear();
    parser1.addString(data);
    if (!parser1.parse()) {Log.warn("parsing failed to parse params\r\n"); return;}
    **// help here... how would I parse the key value into my variable? - char _Key[20]**
    if (!parser1.getOuterValueByKey("aug", newaug)) {Log.warn("failed to get newfan\r\n"); return;}
    if (!parser1.getOuterValueByKey("fan", newfan)) {Log.warn("failed to get newfan\r\n"); return;}
    if (!parser1.getOuterValueByKey("ign", newign)) {Log.warn("failed to get newign\r\n"); return; }

@rickkas7, could you help me here? thank you, Brian

2

Have you had a look at the README.md

Particularly the section about the fluent-style example

String s = parser.getReference().key("response").key("version").valueString();
1 Like
3

yes, thanks. i am sorry I realize I was not clear in my issue description. I did read through that @ScruffR, and I played with the cool parser tool to get the fluent-style command to use, but for my use, i will not know the Key value to insert into the .key("…") function, since it is assigned programatically by Firebase, I need to parse the object (-M5sN1MfCHcXHkLBlwWW) “blindly”, assign it to a string variable so I can use it in my program. Is there a way to grab this? I tried variations of getOuterObject() thinking that might be the right function, but I’m unable to get it to work. Thank you very much for your help.

4

Then you may want to look at getKeyValueByIndex() or getOuterKeyValueByIndex()

5

Hi @ScruffR, thank you for your help. I am working with getOuterKeyValueByIndex() and I have confirmed my library version is 0.1.1. I have a question on the passed variables.

the function calls for: bool getOuterKeyValueByIndex(size_t index, String &key, T &result)
for my example:
index = 0
&key = “” not sure what to use here with no key “name”…just the value -M5sN1MfCHcXHkLBlwWW
T &result = strVal

here’s my current code:

void handler(const char *topic, const char *data) {
    deviceName = String(data);
}
void getDataHandler(const char *event, const char *data) {
    JsonParserStatic<768, 60> parser1;
    parser1.clear();
    parser1.addString(data);

    if (!parser1.parse()) {Log.warn("parsing failed to parse params\r\n"); return;}
 
    String strVal;
    if (!parser1.getOuterKeyValueByIndex(0, "", strVal)) {Log.warn("failed to get Key from json params\r\n"); return;}
    strcpy(Key, strVal); // I strcpy the String into my char variable for my program to use.

I get this error**

no matching function for call to ‘JsonParserStatic<768u, 60u>::getOuterKeyValueByIndex(int, const char [1], String&)’

Can you help me with my sample code? I can’t figure out the syntax since my data (this value I’m trying to grab) is not in a typical Key:Value structure. thanks, Brian

6

The key is what you will get back from the function, so you need to provide a variable to put the key into. You cannot use a constant or string literal like "".

The function signature states that you need to provide a String& (a reference to a String variable) - even when you are not interested in the actualy key name, you need to provide a String to place the name into.

BTW, I don't know whether this is supposed to work, but have you tried fluen style?
e.g.

  String s = parser.getReference().index(0).key("aug").valueBool();
7

I use this library with a firebase get: https://github.com/bblanchon/ArduinoJson

const size_t bufferSize = 3*JSON_ARRAY_SIZE(3) + JSON_OBJECT_SIZE(15) + 150;
    //DynamicJsonBuffer<bufferSize> jsonBuffer;
    StaticJsonBuffer<bufferSize> jsonBuffer;

    // Create a buffer for the json functions, it'll be cleared at function end
    //StaticJsonBuffer<1024> jsonBuffer;

    // Create a char to hold the argument, it'll be cleared at function end
    char charJSON[250];

    // Need to assign across the string
    strArg.toCharArray(charJSON, 250);

    JsonObject& root = jsonBuffer.parseObject(charJSON);

    // Lets make sure to clear this
    //free(charJSON);

    if (!root.success()) {
      Serial.println("parseObject() failed");
      Particle.publish("debug", "ERROR in setPit, parseObject() failed", 60, PRIVATE);


      //delete charJSON;
      // Return error
      return 0;
    } else {
        // do your assignments here. I use a struct for usersettings, so it's like this:
        strcpy(userSettings.fan, root["f"]);
       strcpy(userSettings.pWord, root["alg"][0]);
}
8

If:

  • The outer object contains a single key/value pair and you don’t know the key name in advance
  • You only want the first value

You can use getValueTokenByIndex with a parameter of 1, which is the value associated with the first key/value pair. Here’s the test code I used to verify:

	{
		// {"-M5sN1MfCHcXHkLBlwWW":{"aug":false,"fan":true,"ign":true}}
		JsonParserStatic<256, 14> jp;
		String s;

		char *data = readTestData("test2h.json");

		jp.addString(data);
		free(data);

		bool bResult = jp.parse();
		assert(bResult);

		const JsonParserGeneratorRK::jsmntok_t *firstObject;

		bResult = jp.getValueTokenByIndex(jp.getOuterObject(), 1, firstObject);
		assert(bResult);
		assert(firstObject != 0);

		bool bValue;

		bResult = jp.getValueByKey(firstObject, "aug", bValue);
		assert(bResult);
		assert(bValue == false);

		bResult = jp.getValueByKey(firstObject, "fan", bValue);
		assert(bResult);
		assert(bValue == true);

		bResult = jp.getValueByKey(firstObject, "ign", bValue);
		assert(bResult);
		assert(bValue == true);

	}
1 Like
9

First of all, without you guys @ScruffR @rickkas7 I would not be much of anywhere with my pellet grill smoker control program! Thank you for your help!

Here’s my solution based on your help!

in variables I declare:

const char *PUBLISH_PARAMETERS = "ParametersWrite";
const char *INITIAL_PARAMS_WRITE = "InitialParamsWrite";
const char *READ_PARAMETERS = "KEYParametersRead";

In Setup I declare subscribe and publish…

    Particle.subscribe("hook-response/InitialParamsWrite", getKeyHandler, MY_DEVICES);
    Particle.publish("spark/device/name", NULL, 60, PRIVATE);
    Particle.subscribe("hook-response/KEYParametersRead", getDataHandler, MY_DEVICES);

Since there is no web request: PATCH, I had to first do an IntialParamsWrite to firebase with POST and I grab the firebase key in a webhook response:

{"name":"-M99sRhDVc6yyjc0eNAf"}

then I parse the response in my getkeyHandler to populate my key and postKey variables:

void getKeyHandler(const char *event, const char *data) {
    JsonParserStatic<32, 60> keyParser;
    keyParser.clear();
    keyParser.addString(data);
    
    if (!keyParser.parse()) {Log.warn("parsing of the Key web-hook response failed - failed to parse the params key\r\n"); return;}
    String newKey;
    if (!keyParser.getOuterValueByKey("name", newKey)) {Log.warn("failed to get the key from the webhook params \r\n"); return;}
    strcpy(key, newKey);
}

Then when I WriteParameters, I use PUT and inject the controller{{n}} name and key{{k}} in the url string to basically overlay with my body parameters when they change so this single control record is updated from the photon and from my client Xamarin iOS/Android app.

{
"event": "ParametersWrite",
    "url": "https://someappname.firebaseio.com/ControllerData/{{n}}/Parameters/{{k}}.json",
    "requestType": "PUT",
    "noDefaults": true,
    "rejectUnauthorized": false,
    "query": {
        "auth": "someauthkeyblahblahblahWUbt3oVnfbB"
    },
    "body": "{\"ndex\":{{ndex}},\"Cyc\":{{Cyc}},\"PB\":{{PB}},\"PMode\":{{PMode}},\"PTog\":{{PTog}},\"Td\":{{Td}},\"Ti\":{{Ti}},\"fan\":{{fan}},\"ign\":{{ign}},\"aug\":{{aug}},\"pgm\":{{pgm}},\"mode\":\"{{mode}}\",\"target\":{{target}},\"u\":{{u}} }"
}

then when my ReadParameters web-hook fires I get the response with the nameless key.

{"-M99sRhDVc6yyjc0eNAf": "Cyc":60,"PB":60,"PMode":2,"PTog":0,"Td":45,"Ti":180,"aug":false,"fan":true,"ign":true,"key":"Pellet_Pirate_1","mode":"Start","ndex":1,"pgm":false,"target":200,"u":0.25}}

and I parse this with getDataHandler, using the key I got from my initial write:

void getDataHandler(const char *event, const char *data) {
    JsonParserStatic<768, 60> parser1;
    parser1.clear();
    parser1.addString(data);
 
    if (!parser1.parse()) {Log.warn("%s %.3f getDataHandler: Parameters read failed to parse\r\n", Time.timeStr().c_str(), getTimeWithMillis()); return;}
    newCycle = parser1.getReference().key(key).key("Cyc").valueInt();
    newPB = parser1.getReference().key(key).key("PB").valueInt();
    newPMode = parser1.getReference().key(key).key("PMode").valueInt();
    newPToggle = parser1.getReference().key(key).key("PTog").valueDouble();
    newTd = parser1.getReference().key(key).key("Td").valueInt();
    newTi = parser1.getReference().key(key).key("Ti").valueInt();
    newaug = parser1.getReference().key(key).key("aug").valueBool();
    newfan = parser1.getReference().key(key).key("fan").valueBool();
    newign = parser1.getReference().key(key).key("ign").valueBool();
    String strValue;
	strValue = parser1.getReference().key(key).key("mode").valueString();
	strcpy(newmode, strValue);
	newpgm = parser1.getReference().key(key).key("pgm").valueBool();
	newtarget = parser1.getReference().key(key).key("target").valueInt();
	newu = parser1.getReference().key(key).key("u").valueInt();
}

now just fine tuning the code… thanks again for the help! i hope this helps someone else with their integrations! Carpe Diem!

1 Like
10

This topic was automatically closed 60 days after the last reply. New replies are no longer allowed.