How to parse a json string response using Delphi - json

Question

I have a rest server returning the next json string:
response:='{"result":["[{\"email\":\"XXX#gmail.com\",\"regid\":\"12312312312312312313213w\"},{\"email\":\"YYYY#gmail.com\",\"regid\":\"AAAAAAA\"}]"]}';
I´d like to parse the response to get a list of all email and regid items.
I have tried the next code but I am getting an AV at (TJSONPair(LItem).JsonString.Value='email')
Any help will be appreciated.
Thanks in advance, Luiz
var
LResult:TJSONArray;
LJsonresponse:TJSONObject;
i:integer;
LItem,jv:TJsonValue;
email,regid:string;
LJsonresponse:=TJSONObject.ParseJSONValue(TEncoding.ASCII.GetBytes(response),0) as TJSONObject;
LResult:=(LJsonresponse.GetValue('result') as TJSONArray);
jv:=TJSONArray(LResult.Get(0));
for LItem in TJSONArray(jv) do begin
if (TJSONPair(LItem).JsonString.Value='email') then begin
email:=TJSONPair(LItem).JsonValue.Value;
end;
if (TJSONPair(LItem).JsonString.Value='regid') then begin
regid:=TJSONPair(LItem).JsonValue.Value;
end;
end;

Answer 1

Your problems start here:
jv := TJSONArray(LResult.Get(0));
The problem is that LResult.Get(0) does not return an instance of TJSONArray. In fact it returns an instance of TJSONString. That string has value:
'[{"email":"XXX#gmail.com","regid":"12312312312312312313213w"},{"email":"YYYY#gmail.com","regid":"AAAAAAA"}]'
It looks like you are going to need to parse this string as JSON to extract what you need. Here is some gnarly code that does that. Please excuse its quality because I have no experience at all with the Delphi JSON parser.
{$APPTYPE CONSOLE}
uses
SysUtils, JSON;
const
response =
'{"result":["[{\"email\":\"XXX#gmail.com\",\"regid\":\"12312312312312312313213w\"},'+
'{\"email\":\"YYYY#gmail.com\",\"regid\":\"AAAAAAA\"}]"]}';
procedure Main;
var
LResult: TJSONArray;
LJsonResponse: TJSONObject;
ja: TJSONArray;
jv: TJSONValue;
begin
LJsonResponse := TJSONObject.ParseJSONValue(response) as TJSONObject;
LResult := LJsonResponse.GetValue('result') as TJSONArray;
ja := TJSONObject.ParseJSONValue(LResult.Items[0].Value) as TJSONArray;
for jv in ja do begin
Writeln(jv.GetValue<string>('email'));
Writeln(jv.GetValue<string>('regid'));
end;
end;
begin
try
Main;
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
Readln;
end.
The big lesson here is to stop using unchecked type casts. Using such casts is asking for trouble. When your data does not match your code, you get unhelpful error messages.