Parse JSON using lkJSON - json

Question

I have a JSON file which I need to parse and extract one value.
{
"user": {
"pk": 25025320,
"username": "instagram",
"full_name": "Instagram",
"is_private": false,
"profile_pic_url": "https://instagram.fmad3-5.fna.fbcdn.net/vp/295f9e76d3c26fdf613d7856e7b43348/5B4F495B/t51.2885-19/s150x150/14719833_310540259320655_1605122788543168512_a.jpg",
"profile_pic_id": "1360316971354486387_25025320",
"is_verified": true,
"has_anonymous_profile_picture": false,
"media_count": 5164,
"follower_count": 233901016,
"following_count": 187,
"biography": "Discovering — and telling — stories from around the world.",
"external_url": "",
"usertags_count": 144,
"hd_profile_pic_versions": [
{
"width": 320,
"height": 320,
"url": "https://instagram.fmad3-5.fna.fbcdn.net/vp/893534d61bdc5ea6911593d3ee0a1922/5B6363AB/t51.2885-19/s320x320/14719833_310540259320655_1605122788543168512_a.jpg"
}
],
"hd_profile_pic_url_info": {
"url": "https://instagram.fmad3-5.fna.fbcdn.net/vp/8ae8a89c80ff4722eeab592b685276cb/5B5D40A1/t51.2885-19/14719833_310540259320655_1605122788543168512_a.jpg",
"width": 320,
"height": 320
},
"has_highlight_reels": true,
"auto_expand_chaining": false
},
"status": "ok"
}
I want to extract and send the value of hd_profile_pic_url_info.url to Memo2 using the lkJSON library, Instagram API and code below to achievie this result.
var
sJSON: string;
js, Items, Item: TlkJSONbase;
I, J: Integer;
begin
sJSON := Memo1.text;
js := TlkJSON.ParseText(sJSON);
for I := 0 to Pred(js.Count) do
begin
Items := js.Child[I].Field['user'];
for J := 0 to Pred(Items.Count) do
begin
Item := Items.Child[J];
Memo2.Lines.Add(VarToStr(Item.Field['hd_profile_pic_url_info'].Value));
end;
end;
end;

Answer 1

You forgot that hd_profile_pic_url_info is another object containing url, width, and height, so you need to go down one more time. Here is an example of how this should be done properly.
var
js : TlkJSONbase;
begin
js := TlkJSON.ParseText(Memo1.Text);
if Assigned(js) then
begin
js := js.Field['user'];
if Assigned(js) then
begin
js := js.Field['hd_profile_pic_url_info'];
if Assigned(js) then
begin
js := js.Field['url'];
if Assigned(js) then
Memo2.Lines.Add(VarToStr(js.Value));
end;
end;
end;
end;

Answer 2

i use this function :
function ChildValueStr(AChild: TlkJSONbase; const Name: string; DefaultValue:
AnsiString = ''): {$IF CompilerVersion>=26}WideString{$ELSE}AnsiString{$IFEND};
var
tmpIndex: integer;
tmpStr: {$IF CompilerVersion>=26}WideString{$ELSE}AnsiString{$IFEND};
begin
Result:= DefaultValue;
if IsNil(AChild) then exit;
tmpStr:= (AChild as TlkJSONobject).{$IF CompilerVersion>=26}getWideString{$ELSE}getString{$IFEND}(Name);
if tmpStr = '' then
begin
tmpIndex := (AChild as TlkJSONobject).IndexOfName(Name);
if tmpIndex <> -1 then
Result := (AChild as TlkJSONobject).getString(tmpIndex);
end
else Result:= tmpStr;
end;
so with your code, you can use it :
var sJSON: String;
js, Items, Item: TlkJSONBase;
I, J: Integer;
begin
sJSON := Memo1.text;
js := TlkJSON.ParseText(sJSON);
for I := 0 to Pred(js.Count) do
begin
Items := js.Child[I].Field['user'];
Memo2.Lines.Add(ChildValueStr(Items, 'hd_profile_pic_url_info'));
end;
end;
I hope this can help u

Answer 3

Another alternative to parse JSON without use external components is the free online service https://jsontodelphi.com/
You paste the JSON text and it generate a unit with delphi classes to parse the text without problems. Better if the JSON text is complicated.
In this case, the code to access to the value is simpliest:
procedure TForm2.Button1Click(Sender: TObject);
var
root:TRootClass;
begin
root := TRootClass.FromJsonString(Memo1.Lines.Text {your JSON text});
// The caption get the URL of the pic
Caption := root.user.hd_profile_pic_url_info.url;
end;