How add one object and one pair for a existent .json file? - json

Question

I have a code that changes a value of a determinated pair in a existent JSON file and works perfectly. Now i need add one object and one pair to this file, using great part this same code. So how do this?
Thank you.
uses
System.Json, ShFolder, System.IOUtils;
...
function GetSpecialFolderPath(folder : integer) : string;
const
SHGFP_TYPE_CURRENT = 0;
var
path: array [0..MAX_PATH] of char;
begin
if SUCCEEDED(SHGetFolderPath(0,folder,0,SHGFP_TYPE_CURRENT,#path[0])) then
Result := path
else
Result := '';
end;
procedure ChangeChromeSetting(const ATarget, Avalue: string);
var
specialfolder: integer;
caminhochrome: String;
JSONObj, Obj: TJSONObject;
JSONPair: TJSONPair;
OldValue: string;
begin
specialFolder := CSIDL_LOCAL_APPDATA;
caminhochrome := GetSpecialFolderPath(specialFolder);
caminhochrome := caminhochrome + '\Google\Chrome\User Data\Local State';
if fileexists(caminhochrome) then
begin
Obj := TJSONObject.Create;
JSONObj := TJSONObject.ParseJSONValue(TFile.ReadAllText(caminhochrome)) as TJSONObject;
if not Assigned(JSONObj) then raise Exception.Create('Cannot read file: ' + caminhochrome);
try
OldValue := JSONObj.GetValue<string>(ATarget);
if not SameText(OldValue, Avalue) then
begin
JSONPair := JSONObj.Get(ATarget);
JSONPair.JsonValue.Free;
JSONPair.JsonValue := TJSONString.Create(Avalue);
///////////////////////////////////////////////////
Obj.AddPair('enabled', TJSONBool.Create(false)); // Trying add pair
JSONObj.AddPair('hardware_acceleration_mode', Obj); // Trying add object
//////////////////////////////////////////////////
TFile.WriteAllText(caminhochrome, JSONObj.ToJSON); // Don't add object and pair
end;
finally
JSONObj.Free;
end;
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
ChangeChromeSetting('hardware_acceleration_mode_previous', 'false');
end;
This is result that i'm waiting
"hardware_acceleration_mode":{"enabled":false}

Answer 1

Your code is somewhat confusing since you pass in some of the names as arguments, but then hard code others inside the function. Abstracting functionality is good practise but before you can abstract you really need to ensure the code works correctly. I'm going to show code that does not attempt to be abstract. Once you are satisfied it behaves as you need, then feel free to abstract away.
This code does what I believe is your intent:
var
root: TJSONObject;
value: TJSONObject;
prev: string;
begin
root := TJSONObject.ParseJSONValue(TFile.ReadAllText(FileName)) as TJSONObject;
try
prev := root.GetValue<string>('hardware_acceleration_mode_previous');
if not SameText(prev, 'false') then
begin
// remove existing value, if it exists
root.RemovePair('hardware_acceleration_mode').Free;
// create a new object, and initialise it
value := TJSONObject.Create;
value.AddPair('enabled', 'false');
// add the object at the root level
root.AddPair('hardware_acceleration_mode', value);
// save to file
TFile.WriteAllText(FileName, root.ToJSON);
end;
finally
root.Free;
end;
end;
Note that I have ensured that there are no memory leaks. I've used RemovePair to make sure that if there is an existing value named hardware_acceleration_mode it is first removed.