Delphi REST - How do I know when the data is all retrieved? - rest

Question

In Delphi Tokyo, I have a series of REST components (the ones shipped with Delphi: RESTClient, RESTRequest, RESTResponse, RESTAdapater) tied together to retrieve REST data.
The REST call, as defined on the server, has pagination set to some value.
As such, within my Delphi app I have to repeatedly update the RESTRequest.
ResourceSuffix to add '?page=' and then a page number.
Since various REST Services may have different pagination, or will have different result row counts.
How do I know when I have retrieved all the data?
Surely there is something more elegant that keep trying until rows retrieved = 0/some error.

Answer 1

I found a solution that works for me... My data is coming from Oracle RDBMS, via ORDS and APEX. The REST content (Specifically RAW data) has a URL in it for the next pagination set. For the FIRST set of data, this URL reference is at the end of the REST data stream. For each subsequent data set, the URL reference is at the beginning of the raw data stream, so you have to check both locations. Here is the code I am using...
function IsMoreRESTDataAvailable(Content: String) : Boolean;
var
Test600 : String;
begin
// This routine takes the RESTResponse.Content, aka the raw REST data, and checks to see if there is a NEXT: string
// in either the end of the data (only available for the FIRST DATA set
// or the beginning of the data
result := False;
Test600 := RightStr(Content, 600);
If AnsiPos('"next":{"$ref":"https://<YOUR_SERVER_HERE>', Test600) <> 0 then
begin
result:= True;
Exit;
end;
// If we didn't find it at the end of the REST content, then check at the beginning
Test600 := LeftStr(Content, 600);
If AnsiPos('"next":{"$ref":"https://<YOUR_SERVER_HERE>', Test600) <> 0 then
begin
result:= True;
Exit;
end;
end;