Writing data from MATLAB to firebase database - json

Question

I am using MATLAB to write data from MATLAB to firebase. I am using following lines of code to do so:
thingSpeakURL = 'https://hybrid-cabinet-265907.firebaseio.com/Ship A/Time Stamp.json';
lat = num2str(42);
lon = num2str(42);
data = struct('lat',lat,'lon',lon);
webwrite(thingSpeakURL,data)
Data is successfully written to Firebase. It is making my original JSON data as a child to a random string been generated on run-time.
For example, my JSON string is {lat: '40',lon:'40'} but instead it is creating a random string, let say, "Mxkkllslsll-1112", making that random string as parent and writing something like {"Mxkkllslsll-1112": lat:'40', lon:'40'} to the firebase database.
Please have a look at following image. It shows that for ship A, I have written data from MATLAB and it is not writing properly(I am facing the problem which I discussed above). I want to make it something like data written for Ship B.
I want to write the data without making any random string as a parent. Kindly assist me in that.

Answer 1

This is because webwrite uses the HTTP POST method by default.
As shown in the Firebase Realtime Database REST API documentation, if you do a POST you will push the data and therefore automatically generate a unique key every time a new child is added to the specified Firebase reference (the -MDJVMk..... value we can see in your question).
You need to use the PUT method.
I don't know matlab but a rapid look at the documentation shows that you need to use the RequestMethod option with a put value, in the weboptions object.

Answer 2

The above pushed me in the right direction (thanks!), and I had success with the following.
CAUTION: The following will overwrite everything in your database!
url = 'https://***.firebaseio.com/.json';
data.users(1) = struct('first','John','last','Locke');
data.users(2) = struct('first','Thomas','last','Hobbes');
data.users(3) = struct('first','Rene','last','Descartes');
headers = {'Content-Type' 'application/json'; 'Accept' 'application/json'};
options = weboptions('RequestMethod', 'put', 'HeaderFields', headers, 'ArrayFormat', 'json');
response = webwrite(url, data, options);
If your data is stored in a .json file (i.e., you don't want to create structures manually in Matlab), you can read it using "fileread" and pass in data as a string (instead of a structure).