JSON Array From URL in DELPHI-CodePudding

I have the following Json Array from url link.

[{"DATE":"01/10/2021","QUANTITY":4,"UNITPRICE":23.9}, 
 {"DATE":"01/10/2021","QUANTITY":5.85,"UNITPRICE":23.9}, 
 {"DATE":"30/09/2021","QUANTITY":10,"UNITPRICE":23.9}, 
 {"DATE":"04/08/2021","QUANTITY":10,"UNITPRICE":28.83}, 
 {"DATE":"01/07/2021","QUANTITY":1,"UNITPRICE":2.06}, 
 {"DATE":"01/07/2021","QUANTITY":1,"UNITPRICE":2.06}, 
 {"DATE":"30/06/2021","QUANTITY":1,"UNITPRICE":2.06}, 
 {"DATE":"30/06/2021","QUANTITY":1,"UNITPRICE":2.06}]

I want to extract a particular data from the above kind of JSON structure and later to Show in Memo or ListView the values of DATE or one of the other elements.The proper thing to do is to create an Array of Json and put the data in? When i run my code and click the button it doesnt show anything. Also Im new to Delphi. Here is the code i have wrote:

 function GetURLAsString(const aurl: string): string;
  var
   IdHTTP1 : TidHTTP;
  begin
  IdHTTP1 := TIdHTTP.Create(nil);
  try
   IdHTTP1.IOHandler := TidSSLIOHandlerSocketOpenSSL.Create(IdHTTP1);
   result := IdHTTP1.Get(aurl);
  finally
   IdHTTP1.Free;
  end;
 end;


procedure TForm4.Button1Click(Sender: TObject);
var
jso : TJsonObject;
 js : TJsonObject;
jsv : TJsonValue;
jsa : TJsonArray;
jsp : TJsonPair;
data : string;
  i : integer;
LItem : TListViewItem;

begin

try
  data := GetURLAsString('http://....');
except
  on E: exception do
end;

try
  jsv := TJSONObject.ParseJSONValue(data);

  try

    jso := jsv as TJSONObject;
    jsa:=TJSONArray.Create();
    jsp := TJSONPair.Create('Array', jsa);
    js.AddPair(jsp);
    jsp := jso.Get('Array');
    jsa := jsp.JsonValue as TJsonArray;
     for I  := 0 to jsa.Size - 1 do
        begin
           jso := jsa.Get(i) as TJsonObject;

           for jsp in jso do
             begin
                 if jsp.JsonString.Value  = 'DATE' then
                 begin
                    form4.ListView1.BeginUpdate;
                    LItem := form4.ListView1.Items.Add;
                    LItem.Text := jso.GetValue('DATE').ToString;
                    form4.ListView1.EndUpdate;
                 end;

             end;
        end;

    finally
      jsv.Free;
    end;
  except
   on E: exception do
  end;

end;

CodePudding user response：

I suspect you will get an access violation because you access the method AddPair of the js variable which has not been initialized, and since you catch the exception and igores it, you do not see it.

You are however overcomplicating the solution, which results in bugs. This should work:

jsa := jsv as TJSONArray;
form4.ListView1.BeginUpdate;
try
 for I  := 0 to jsa.Size - 1 do
    begin
       jso := jsa.Get(i) as TJsonObject;
       LItem := form4.ListView1.Items.Add;
       LItem.Text := jso.GetValue('DATE').ToString;
    end;

 finally
  form4.ListView1.EndUpdate;
 end;
finally
  jsv.Free;
end;