Unable to Parse JSON with Delphi - json

Question

I have a JSON string which comes from Amazon. (https://pricing.us-east-1.amazonaws.com/offers/v1.0/aws/index.json) The top of the JSON looks like this...
I need to retrieve a list of JUST the offerCode and versionIndexUrl values. I can read an array of offers, but the key of each offer is different, so I can't use the NAME(comprehend, AmazonMWAA, etc). I have tried using element [0] but I get an AV. Here is my relevant code...
procedure Load_AWS_Services;
var
json: string;
idx: Integer;
obj: TJSONObject;
j_array: TJSONArray; // the array of all lineitems/offers
lineItem : TJSONObject;
ServiceEntry: TJSONPair;
begin
try
JSON := DownloadFromURLasString('https://pricing.us-east-1.amazonaws.com/offers/v1.0/aws/index.json');
obj := TJSONObject.ParseJSONValue(JSON) as TJSONObject;
try
// Now parse the data...
j_array := TJSONArray(obj.Get('offers').JsonValue);
// Now loop through each individual item
for idx := 0 to pred(j_array.size) do
begin
lineItem := TJSONObject(j_array.Get(idx));
Main.Memo1.Lines.Add(lineItem.ToString); // this shows each offer...so good to this point
ServiceEntry := lineItem.Pairs[0];
ShowMessage(ServiceEntry.Value); // AV here
What do I need to change in my last 2 lines to read INSIDE the 'offers'?

Answer 1

The offers field is a JSON object, not a JSON array (had you used the as operator for the TJSONArray cast, you would have gotten an EInvalidCast exception raised).
Try this instead:
procedure Load_AWS_Services;
var
json: string;
idx: Integer;
j_val: TJSONValue;
j_obj: TJSONObject;
j_pair: TJSONPair;
offers: TJSONObject;
lineItem : TJSONObject;
begin
try
json := DownloadFromURLasString('https://pricing.us-east-1.amazonaws.com/offers/v1.0/aws/index.json');
j_val := TJSONObject.ParseJSONValue(json);
try
j_obj := j_val as TJSONObject;
// Now parse the data...
offers := j_obj.GetValue('offers') as TJSONObject;
// Now loop through each individual item
for idx := 0 to pred(offers.Count) do
begin
j_pair := offers.Get(idx);
Main.Memo1.Lines.Add(j_pair.JsonString.Value);
lineItem := j_pair.JsonValue as TJSONObject;
ShowMessage(lineItem.GetValue('offerCode').Value);
ShowMessage(lineItem.GetValue('versionIndexUrl').Value);
...
end;
finally
j_val.Free;
end;
except
...
end;
end;