Flutter put request for Database - json

Question

I am working on a Flutter app. we have a PSQL database, Node server on the background. On the Flutter app I am displaying some geometry which I fetch from the database successfully. Now after a modification on the geometry, such as lines, I want to be able to update the database via a put request.
Server goes like:
app.put('/api/shape/:id', async (req,res) =>{
let answer;
if( req.body.shape_type == "line"){
answer = await db.db.modify_line(req.params.id, req.body.info_shape);
}
res.send(answer);
});
And db.js file goes like:
modify_line : async function(id_shape, info_shape){
console.log(info_shape);
const result = await send_query("UPDATE line SET line = $2 WHERE id_shape = $1", [id_shape, info_shape]);
return(result);
},
On the Flutter app I do this:
_makeUpdateRequest() async {
var url = globals.URL + 'api/shape/' + globals.selectedShapeID.toString();
Map data;
if (globals.selectedType == globals.Type.line) {
String lseg = "(" + globals.pLines[globals.selectedLineIndex].p1.dx.toString() + "," +
globals.pLines[globals.selectedLineIndex].p1.dy.toString() + "," +
globals.pLines[globals.selectedLineIndex].p2.dx.toString() + "," +
globals.pLines[globals.selectedLineIndex].p2.dy.toString() + ")";
data = {
'shape_type': 'line',
'info_shape': {
'id_shape': globals.selectedShapeID.toString(),
'line': lseg,
}
};
}
http.Response response;
try {
//encode Map to JSON
print("encode Map to JSON");
var body = json.encode(data);
print(body);
response =
await http.put(url,
headers: {
"Content-Type": "application/json"
},
body: body
).catchError((error) => print(error.toString()));
} catch (e) {
print(e);
}
return response;
}
Database "line" table contains a "shapeID" and "lseg" information on each row.
Currently I am getting an error when I try this code:
{ id_shape: '619',
line: '(19.5,100.6,20.5,50.9)' }
fail____error: invalid input syntax for type lseg: "{"id_shape":"619","line":"(-19.5,100.6,20.5,50.9)"}"
How shall I shape my lseg json?
Thanks

Answer 1

Well, it looks like to me you are passing the whole input_shape object to the SQL query, which looks like this, as per your console.log:
{
id_shape: '619',
line: '(19.5,100.6,20.5,50.9)'
}
Obviously, this is invalid for PostgreSQL.
I would say that your backend code should be more like this:
modify_line : async function(id_shape, info_shape){
console.log(info_shape);
const result = await send_query(
"UPDATE line SET line = $2 WHERE id_shape = $1",
// Reference "line" sub-object
[id_shape, info_shape.line],
);
return(result);
},
You should also pay attention to the Geometric types format for lines:
[ ( x1 , y1 ) , ( x2 , y2 ) ]
( ( x1 , y1 ) , ( x2 , y2 ) )
( x1 , y1 ) , ( x2 , y2 )
x1 , y1 , x2 , y2
I'm not 100% sure by reading this that your format (with leading and trailing parenthesis) is correct.

Answer 2

As the issue is solved, following is the answer:
DB.js is like:
modify_line : async function(id_shape, info_shape){
const result = await send_query("UPDATE line SET line = $2 WHERE id_shape = $1", [info_shape['id_shape'], info_shape['line']]);
return(result);
},
and Flutter app is like:
_makeUpdateRequest() async {
var url = globals.URL + 'api/shape/' + globals.selectedShapeID.toString();
Map data;
if (globals.selectedType == globals.Type.line) {
String lseg =
"[" + globals.pLines[globals.selectedLineIndex].p1.dx.toString() + "," +
globals.pLines[globals.selectedLineIndex].p1.dy.toString() + "," +
globals.pLines[globals.selectedLineIndex].p2.dx.toString() + "," +
globals.pLines[globals.selectedLineIndex].p2.dy.toString() + "]";
data = {
'shape_type': 'line',
'info_shape': {
'id_shape': globals.selectedShapeID.toString(),
'line': lseg,
}
};
}
http.Response response;
try {
//encode Map to JSON
print("encode Map to JSON");
var body = json.encode(data);
print(body);
response =
await http.put(url,
headers: {
"Content-Type": "application/json"
},
body: body
).catchError((error) => print(error.toString()));
} catch (e) {
print(e);
}
return response;
}