Title here
Summary here
Json in Modelica
Our first program will demonstrate JSON encoding and decoding in Modelica. Here’s the full source code and explanation:
model JSONExample
import Modelica.Utilities.Strings;
import Modelica.Utilities.Files;
import Modelica.Utilities.Streams;
record Response
Integer page;
String[:] fruits;
end Response;
function encodeJSON
input Response response;
output String json;
algorithm
json := "{\"page\":" + String(response.page) + ",\"fruits\":[";
for i in 1:size(response.fruits, 1) loop
json := json + "\"" + response.fruits[i] + "\"";
if i < size(response.fruits, 1) then
json := json + ",";
end if;
end for;
json := json + "]}";
end encodeJSON;
function decodeJSON
input String json;
output Response response;
protected
Integer startIndex, endIndex;
String pageStr, fruitsStr;
algorithm
// Extract page
startIndex := Strings.find(json, "\"page\":");
endIndex := Strings.find(json, ",", startIndex=startIndex);
pageStr := Strings.substring(json, startIndex+7, endIndex-1);
response.page := Integer(pageStr);
// Extract fruits
startIndex := Strings.find(json, "\"fruits\":[");
endIndex := Strings.find(json, "]", startIndex=startIndex);
fruitsStr := Strings.substring(json, startIndex+10, endIndex-1);
response.fruits := Strings.split(fruitsStr, "\",\"");
for i in 1:size(response.fruits, 1) loop
response.fruits[i] := Strings.replace(response.fruits[i], "\"", "");
end for;
end decodeJSON;
equation
// Encoding example
Response response1(page=1, fruits={"apple", "peach", "pear"});
String encodedJSON = encodeJSON(response1);
Streams.print("Encoded JSON: " + encodedJSON);
// Decoding example
String jsonString = "{\"page\":2,\"fruits\":[\"banana\",\"mango\"]}";
Response decodedResponse = decodeJSON(jsonString);
Streams.print("Decoded page: " + String(decodedResponse.page));
Streams.print("Decoded fruits: " + Strings.toString(decodedResponse.fruits));
end JSONExample;In this Modelica example, we’ve created a simple JSON encoder and decoder for a custom Response record. Here’s a breakdown of the code:
We define a
Responserecord to hold our data structure.The
encodeJSONfunction takes aResponseobject and converts it to a JSON string.The
decodeJSONfunction takes a JSON string and converts it back to aResponseobject.In the equation section, we demonstrate both encoding and decoding:
- We create a
Responseobject, encode it to JSON, and print the result. - We define a JSON string, decode it to a
Responseobject, and print the decoded values.
- We create a
This example showcases basic JSON handling in Modelica. Note that Modelica doesn’t have built-in JSON support, so we’ve implemented a simple version of JSON encoding and decoding. For more complex JSON operations, you might want to use external C functions or libraries.
To run this example, you would typically include it in a Modelica simulation environment. The output would show the encoded JSON string and the decoded values from the JSON string.
Remember that Modelica is primarily used for physical system modeling and simulation, so JSON handling is not a core feature of the language. In practice, JSON operations might be performed using external functions or pre/post-processing steps in a Modelica workflow.