Help with retrieving one document and extracting the document fields into variables (ESP32 and Cloud Firestore)

[tanseowsean]

Referring to the example at https://github.com/mobizt/Firebase-ESP-Client/blob/main/examples/Firestore/GetDocument/GetDocument.ino, the retrieval of one document can be carried out in this manner:

How do I retrieve the fields in the document to be stored into variables for comparison/processing purposes? Is there any way to do so?

[mobizt]

You should parse your document for required fields. You also can use runQuery to filter the result.

[mobizt]

For the compilation error, your library installation is not complete or missing something or deprecated version installed.

You should delete library from Arduino libraries folder and install the lastest version via Library Manager.

The last error is the stack trace after device crashed.

It is not related to the code you mentioned, i.e.
values.set("integerValue", "-1")

It is the error from your code that trying to access or use something that does not exist in memory.

You should learn to debug your code, and decode the stack traces, search Google for how to.

[mobizt]

Assing negative value for increment write is ok as this operation supports int64 and double that can be positive/negative value that does not overflow.

[tanseowsean]

Is it possible for you to provide me with an example of querying a single document's field and then parse the value into a variable? Would appreciate a simple example as the provided examples are for multiple documents from a single collection (if I did not interpret mistakenly)

What does it mean by query at collection c0 to get the 3 documents in the payload result? Sorry for the hassle and thank you.

[mobizt]

You need to know the Firestore REST API to use the library.

And you should understand the function parameters related to the Firestore REST API.

The library function description for runQuery is here.

Firebase-ESP-Client/examples/Firestore/DataQuery/DataQuery.ino

Line 150 in 277a2ab

// https://github.com/mobizt/Firebase-ESP-Client/tree/main/src#runs-a-query

And you will see the link to Firestore REST API documentation related to that function and parameters.

[mobizt]

You will see that the limit property in the query is related to your both questions.

The limit and other properties of StructuredQuery were described here.

You can't apply further than the Firestore examples that provided by the library without the understanding of Firestore REST API that used in this library.

[tanseowsean]

I see, I am not using the API, hence, it did not work for me as I am only importing your Firebase ESP Client library. Thank you very much!