Reading and writing JSON in Inno Setup

Question

How can I load and work with JSON config file during install time? I can read string from file and write it, but if I want to change some value in config file, I have to use `VBScript.RegExp` COM object (which is good, but painful and slow to develop). Current method: ``` ExtractTemporaryFile('config.json'); filename := ExpandConstant('{tmp}\config.json'); LoadStringFromFile(filename, conf); objRegExp := CreateOleObject('VBScript.RegExp'); objRegExp.Pattern := 'test'; conf := objRegExp.Replace(conf, 'test_replace'); SaveStringToFile(filenameOut, conf, False); ``` Is there a better way to do this? All I need is to replace some values in JSON object, no extra magic.

Accepted Answer

I've setup the new project called `Inno JSON Config`, which allows you to work with simple JSON config files like shown below and which allows you to read and write string, integer and boolean values:

```
{
    "Section_1":{
            "Key_1": "String 1",
            "Key_2": "1",
            "Key_3": "True"
    },
    "Section_2":{
            "Key_1": "String 2",
            "Key_2": "2",
            "Key_3": "False"
    }
}
```

The usage is quite straightforward (even when I'm going to add handle support as well). Note, that only Unicode Inno Setup (in one of the most recent versions due to a required `Int64` support) can be used:

```
[Files]
Source: "JSONConfig.dll"; Flags: dontcopy

[Code]
function JSONQueryString(FileName, Section, Key, Default: WideString;
  var Value: WideString; var ValueLength: Integer): Boolean;
  external 'JSONQueryString@files:jsonconfig.dll stdcall';
function JSONQueryBoolean(FileName, Section, Key: WideString; 
  Default: Boolean; var Value: Boolean): Boolean;
  external 'JSONQueryBoolean@files:jsonconfig.dll stdcall';
function JSONQueryInteger(FileName, Section, Key: WideString; 
  Default: Int64; var Value: Int64): Boolean;
  external 'JSONQueryInteger@files:jsonconfig.dll stdcall';
function JSONWriteString(FileName, Section, Key, 
  Value: WideString): Boolean;
  external 'JSONWriteString@files:jsonconfig.dll stdcall';
function JSONWriteBoolean(FileName, Section, Key: WideString;
  Value: Boolean): Boolean;
  external 'JSONWriteBoolean@files:jsonconfig.dll stdcall';
function JSONWriteInteger(FileName, Section, Key: WideString;
  Value: Int64): Boolean;
  external 'JSONWriteInteger@files:jsonconfig.dll stdcall';

function BoolToStr(Value: Boolean): string;
begin
  Result := 'True';
  if not Value then
    Result := 'False';
end;

procedure InitializeWizard;
var
  FileName: WideString;
  IntValue: Int64;
  StrValue: WideString;
  StrLength: Integer;
  BoolValue: Boolean;
begin
  { set the source JSON config file path }
  FileName := 'c:\Example.json';
  { allocate string buffer to enough length }
  SetLength(StrValue, 16);
  { set the buffer length value }
  StrLength := Length(StrValue);
  { query string value }
  if JSONQueryString(FileName, 'Section_1', 'Key_1', 'Default', StrValue, 
    StrLength)
  then
    MsgBox('Section_1:Key_1=' + StrValue, mbInformation, MB_OK);
  { query integer value }
  if JSONQueryInteger(FileName, 'Section_1', 'Key_2', 0, IntValue) then
    MsgBox('Section_1:Key_2=' + IntToStr(IntValue), mbInformation, MB_OK);
  { query boolean value }
  if JSONQueryBoolean(FileName, 'Section_1', 'Key_3', True, BoolValue) then
    MsgBox('Section_1:Key_3=' + BoolToStr(BoolValue), mbInformation, MB_OK);
  { write string }
  if not JSONWriteString(FileName, 'Section_1', 'Key_1', 'New value!') then
    MsgBox('JSONWriteString Section_1:Key_1 failed!', mbError, MB_OK);
  { write integer }
  if not JSONWriteInteger(FileName, 'Section_1', 'Key_2', 123) then
    MsgBox('JSONWriteInteger Section_1:Key_2 failed!', mbError, MB_OK);
  { write boolean }
  if not JSONWriteBoolean(FileName, 'Section_1', 'Key_3', False) then
    MsgBox('JSONWriteBoolean Section_1:Key_3 failed!', mbError, MB_OK);
end;
```

Reading and writing JSON in Inno Setup

Solution

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