JSONTools Array

[pcurtis]

I have the following array :

TMyArray = array [0..9] of integer;

How do I store and retrieve this array using JSONTools?

I know there is a type nkArray, but I dont know how to use it.

Any ideas / help please?

[mangakissa]

Code: Pascal  [Select][+][-]

1.     procedure TForm1.BtnCreateClick(Sender: TObject);
2.     var  MyArray         : TJSONArray;
3.           TS              : TStringstream;
4.      
5.     function ObjToArray(aName : string; aAge : integer) : TJSONObject;
6.     begin
7.      result := TJSONObject.Create;
8.      result.Add('name', aName);
9.      result.Add('age', aAge);
10.     end;
11.      
12.     begin
13.     MyArray := TJSONArray.Create;
14.      MyArray.Add(ObjToArray('john',50));
15.      MyArray.Add(ObjToArray('peter',40));
16.      TS      := TStringstream.Create(MyArray.AsJSON);
17.      memo1.lines.add(TS.DataString);
18.     MyArray.free;
19.     end;
20.  

[pcurtis]

Does that use JSONTools ?

[TRon]

Does that use JSONTools ?

No, but following code does.

Code: Pascal  [Select][+][-]

1. program array2json;
2.  
3. {$MODE OBJFPC}{$H+}
4.  
5. uses
6.   sysutils, jsontools;
7.  
8. type
9.   TMyArray= array [0..9] of integer;
10.  
11. function example1(AArray: TMyArray): TJSonNode;
12. var
13.   n: integer;
14. begin
15.   // Create a node
16.   Result:= TJSONNode.Create;
17.  
18.   // Make this node an array
19.   Result.kind:= nkArray;
20.  
21.   // Fill, this now, array node. Note that for adding values to an array their name is discarded (hence empty)
22.   for n in AArray
23.     do Result.Add('', n);
24. end;
25.  
26. function example2(ANode: TJSonNode; AName: String; AArray: TMyArray): TJSonNode;
27. var
28.   JSonArray: TJSonNode;
29.   n: integer;
30. begin
31.   // Adding an array node with provided name
32.   JSonArray:= ANode.Add(AName, nkArray);
33.  
34.   // Fill the array node. Note that for adding values to an array their name is discarded (hence empty)
35.   for n in AArray
36.     do JSonArray.Add('', n);
37.  
38.   // Return node to caller
39.   result:= ANode;
40. end;
41.  
42.  
43. function example3(AArray: TMyArray): TJSonNode;
44. var
45.   n: integer;
46.   i: integer;
47.   s: string;
48. begin
49.   // Create a node
50.   Result:= TJSONNode.Create;
51.  
52.   // Make this node an array
53.   Result.kind:= nkArray;
54.  
55.   // convert the array to a string
56.   s:= '[';
57.   for i:= low(AArray) to High(AArray) do
58.   begin
59.     s:= s+AArray[i].ToString;
60.     if i<High(AArray) then s:= s+',';
61.   end;
62.   s:= s+']';
63.  
64.   // set the value of the array
65.   Result.Value:= s;
66. end;
67.  
68. var
69.   MyArray: TMyArray= (10,9,8,7,6,5,4,3,2,1);
70.   JSon: TJSonNode;
71.  
72. begin
73.   // example 1: returns JSONNode as array
74.   WriteLn('--- example 1 ---');
75.   JSon:= example1(MyArray);
76.   WriteLn(JSon.ToString);
77.   JSon.Free;
78.  
79.   // example 2: add (named) array to (existing) node
80.   WriteLn('--- example 2 ---');
81.   JSon:= TJSonNode.Create;
82.   JSon:= example2(JSon, 'My_Array', MyArray);
83.   WriteLn(JSon.ToString);
84.   JSon.Free;
85.  
86.   // example 3: return JSonNode as array using text conversion
87.   JSon:= example3(MyArray);
88.   WriteLn(JSon.ToString);
89.   JSon.Free;
90. end.
91.  

There are for sure more methods you could use but these seem to be the most obvious ones to me.

edit: stupid typo in code, 3th example was invoking example1, corrected now.

[pcurtis]

Thanks TRon,

How do read the node back to the array?

Thanks.

[TRon]

How do read the node back to the array?

Good that you realised to ask the proper question (e.g. I assume you were not waiting on a "yes" answer) 

Sorry for teasing...

Code: Pascal  [Select][+][-]

1. program json2array;
2.  
3. {$MODE OBJFPC}{$H+}
4.  
5. uses
6.   sysutils, jsontools;
7.  
8. type
9.   TMyArray= array [0..9] of integer;
10.  
11. function example1(JSon: TjSonNode): TMyArray;
12. var
13.   i: integer;
14.   childnode: TjSonNode;
15. begin
16.   // fill array with default values
17.   result:= default(TMyarray);
18.  
19.   // are we dealing with a json array ?
20.   if JSon.Kind=nkArray then
21.   begin
22.     // do the lengths of the arrays match ?
23.     if JSon.Count=Length(Result) then
24.     begin
25.       // init array index
26.       i:= Low(Result);
27.       // iterate through json array
28.       for childNode in JSon do
29.       begin
30.         // is this item in the array a number ?
31.         if childNode.Kind=nkNumber then
32.         begin
33.           // pray and hope this child contains an integer
34.           Result[i]:= childnode.value.ToInteger;
35.         end
36.         else WriteLn('json array item is not a number so won''t fit in returning array');
37.         inc(i);
38.       end;
39.     end
40.     else WriteLn('array does not contain as many items as array does');
41.   end
42.   else Result:= default(TMyArray);
43. end;
44.  
45. var
46.   MyArray: TMyArray;
47.   JSon: TJSonNode;
48.   n: integer;
49. begin
50.   JSon := TJSonNode.Create;
51.   try
52.     JSon.Kind:= nkArray;
53.     JSon.Value:= ('[10,9,8,7,6,5,4,3,2,1]');
54.  
55.     // example1 - convert json array to TMyArray
56.     WriteLn('--- example 1 ---');
57.     MyArray:= default(TMyArray);
58.     Write('before: ');for n in MyArray do Write(n,' ');WriteLn;  
59.     // provide array node in order to transfer content to MyArray
60.     MyArray:= example1(JSon);  
61.     Write('after: ');for n in MyArray do Write(n,' ');WriteLn;
62.   finally
63.     JSon.Free;
64.   end;
65. end.
66.  

Please, do realise there are some pitfalls there. I tried to express/address them as many as possible in the code. You would have to address some of these issues inside your own code using your own solution(s), e.g. what to do if not all array items are numbers, what i the sizes do not match and, what to do if a number does not convert properly to an integer etc.

[pcurtis]

Thanks for your help.