Delphi TRestRequest array parameter

Question

This might be a simple one.

I'm accessing a RESTFul service with Delphi XE6 using RestClient components: TRestClient, TRestRequest, TRestResponse and THTTPBasicAuthenticator.

The service requires parameters which I have no problems adding:

RestReq.Params.AddItem('param1', 'value1');
RestReq.Params.AddItem('param2', 'value2');

With the above code on the server side it looks like:

{
  "param1":"value1",
  "param2":"value2"
}

However, when I need to send a parameter which is an array and I try:

RestReq.Params.AddItem('param1', 'value1');
RestReq.Params.AddItem('param2', 'value2');
RestReq.Params.AddItem('param3', '[v1, v2, v3]');

The service will reject it because the third parameter is not the expected array. Which is correct because it receives:

{
  "param1":"value1",
  "param2":"value2",
  "param3":"[v1,v2,v3]"
}

I know it looks very simple. Have switched RestClient.ContentType, have tried to manipulate the array. Have tried changing the parameter ContentType, Options and guessing the solution is not a game I like to play. So the question would be: Using the RestClient components ¿how can I call my service with the following parameters?

{
  "param1":"value1",
  "param2":"value2",
  "param3":[
    "v1",
    "v2",
    "v3"
  ]
}

In advance, thanks for your time.

I have absolutely no knowledge of REST or JSON, so only a comment, but did you try: RestReq.Params.AddItem('["v1", "v2", v3"]');? It is the first thing I would try. — Rudy Velthuis
– Rudy Velthuis, Commented Jul 29, 2014 at 18:58
What if you set the Options for the parameter to poDoNotEncode? — Graymatter
– Graymatter, Commented Jul 29, 2014 at 23:21

Gixabel · Accepted Answer · 2014-07-30 21:37:12Z

2

Done! It looks like I was doing it the wrong (or complicated) way. The service was expecting a JSON object and I was building it property by property. There is an easier way:

var aParam: TRESTRequestParameter;
begin
  RestReq.Method := rmPOST; {or rmGET, ...}
  aParam := RestReq.Params.AddItem(); //don't care about setting a name for it
  aParam.Value := TJSONObject.ParseJSONValue('{"param1":"value1","param2":"value2","param3":["v1","v2","v3"]}');
  aParam.ContentType := ctAPPLICATION_JSON;
  //set proxy params, resource, etc.
  RestClient.Execute();
end;

And that will do! Thanks all for your comments.

answered Jul 30, 2014 at 21:37

Gixabel

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2 Comments

Ydakilux Over a year ago

In my case with XE7 I must write aParam.Value := '{"param1":"value1","param2":"value2","param3":["v1","v2","v3"]}';

user424855 Over a year ago

In my case with Tokyo 10.2, I used aParam.Value := TJSONObject.ParseJSONValue('{"a":"b"}').ToJSON;

peardox · Accepted Answer · 2025-06-14 18:24:08Z

0

While looking for this in releation to some public API I ended up here so to help anyone with a similar issue there's a way to encode arrays into a query string although the documentation (as usual) is less than easy to find.

e.g.

uses
  REST.Client, REST.Types;

...

  RESTRequest := TRESTRequest.Create(Nil);

  RESTParams := TRESTRequestParameterList.Create(Nil);
  // Add any normal parameters e.g.
  RESTParams.AddItem('output','json'); // etc - any easy ones
  // And here's an array for fl[] with multiple values
  RESTParams.AddItem('fl','avg_rating;creator;date', pkGETorPOST, [poPHPArray]);

  RESTRequest.Params := RESTParams;

  // Add other stuff now the params are correctly set

See TRESTRequestParameterOption for other variants instead of poPHPArray

edited Jun 14 at 18:24

answered Jun 14 at 18:18

peardox

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