(Delphi DLL) JSON Paths

Demonstrates using "Chilkat JSON Paths" to access parts of a JSON document, or to iterate over parts.

This example uses the following JSON document:

{
    "nestedArray" : [
			[
				[1,2,3],
				[4,5,6],
				[7,8,9,10]
			],
			[
				[11,12,13],
				[14,15,16],
				[17,18,19,20]
			],
			[
				[21,22,23],
				[24,25,26],
				[27,28,29,30],
				[31,32,33,34,35,36]
			]
		],

	"nestedObject" : {
		"aaa" : {
			"bb1" : {
				"cc1" : "c1Value",
				"cc2" : "c2Value",
				"cc3" : "c3Value"
			},
			"bb2" : {
				"dd1" : "d1Value",
				"dd2" : "d2Value",
				"dd3" : "d3Value"
			}
		}
	},

	"mixture" : {
		"arrayA" : [  
			{ "fruit": "apple", "animal": "horse", "job": "fireman", "colors": ["red","blue","green"] },
			{ "fruit": "pear", "animal": "plankton", "job": "waiter", "colors": ["yellow","orange","purple"] },
			{ "fruit": "kiwi", "animal": "echidna", "job": "astronaut", "colors": ["magenta","tan","pink"] }
			]
	},


        "name.with.dots" : { "grain" : "oats" }

	
}

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, JsonArray, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
json: HCkJsonObject;
sz: Integer;
i: Integer;
j: Integer;
k: Integer;
szI: Integer;
szJ: Integer;
szK: Integer;
obj2: HCkJsonObject;
arr1: HCkJsonArray;
szArr1: Integer;

begin
success := False;

json := CkJsonObject_Create();
CkJsonObject_putEmitCompact(json,False);

// Assume the file contains the data as shown above..
success := CkJsonObject_LoadFile(json,'qa_data/json/pathSample.json');
if (success = False) then
  begin
    Memo1.Lines.Add(CkJsonObject__lastErrorText(json));
    Exit;
  end;

// First, let's get the value of "cc1"
// The path to this value is: nestedObject.aaa.bb1.cc1
Memo1.Lines.Add(CkJsonObject__stringOf(json,'nestedObject.aaa.bb1.cc1'));

// Now let's get number 18 from the nestedArray.
// It is located at nestedArray[1][2][1]
// (remember: Indexing is 0-based)
Memo1.Lines.Add('This should be 18: ' + IntToStr(CkJsonObject_IntOf(json,'nestedArray[1][2][1]')));

// We can do the same thing in a more roundabout way using the 
// I, J, and K properties.  (The I,J,K properties will be convenient
// for iterating over arrays, as we'll see later.)
CkJsonObject_putI(json,1);
CkJsonObject_putJ(json,2);
CkJsonObject_putK(json,1);
Memo1.Lines.Add('This should be 18: ' + IntToStr(CkJsonObject_IntOf(json,'nestedArray[i][j][k]')));

// Let's iterate over the array containing the numbers 17, 18, 19, 20.
// First, use the SizeOfArray method to get the array size:
sz := CkJsonObject_SizeOfArray(json,'nestedArray[1][2]');
// The size should be 4.
Memo1.Lines.Add('size of array = ' + IntToStr(sz) + ' (should equal 4)');

// Now iterate...

for i := 0 to sz - 1 do
  begin
    CkJsonObject_putI(json,i);
    Memo1.Lines.Add(IntToStr(CkJsonObject_IntOf(json,'nestedArray[1][2][i]')));
  end;

// Let's use a triple-nested loop to iterate over the nestedArray:

// szI should equal 1.
szI := CkJsonObject_SizeOfArray(json,'nestedArray');
for i := 0 to szI - 1 do
  begin
    CkJsonObject_putI(json,i);

    szJ := CkJsonObject_SizeOfArray(json,'nestedArray[i]');
    for j := 0 to szJ - 1 do
      begin
        CkJsonObject_putJ(json,j);

        szK := CkJsonObject_SizeOfArray(json,'nestedArray[i][j]');
        for k := 0 to szK - 1 do
          begin
            CkJsonObject_putK(json,k);

            Memo1.Lines.Add(IntToStr(CkJsonObject_IntOf(json,'nestedArray[i][j][k]')));
          end;

      end;

  end;

// Now let's examine how to navigate to JSON objects contained within JSON arrays.
// This line of code gets the value "kiwi" contained within "mixture"
Memo1.Lines.Add(CkJsonObject__stringOf(json,'mixture.arrayA[2].fruit'));

// This line of code gets the color "yellow"
Memo1.Lines.Add(CkJsonObject__stringOf(json,'mixture.arrayA[1].colors[0]'));

// Getting an object at a path:
// This gets the 2nd object in "arrayA"

obj2 := CkJsonObject_Create();
CkJsonObject_ObjectOf2(json,'mixture.arrayA[1]',obj2);

// This object's "animal" should be "plankton"
Memo1.Lines.Add(CkJsonObject__stringOf(obj2,'animal'));

// Note that paths are relative to the object, not the absolute root of the JSON document.
// Starting from obj2, "purple" is at "colors[2]"
Memo1.Lines.Add(CkJsonObject__stringOf(obj2,'colors[2]'));

// Getting an array at a path:
// This gets the array containing the colors red, green, blue:

arr1 := CkJsonArray_Create();
CkJsonObject_ArrayOf2(json,'mixture.arrayA[0].colors',arr1);

szArr1 := CkJsonArray_getSize(arr1);
for i := 0 to szArr1 - 1 do
  begin
    Memo1.Lines.Add(IntToStr(i) + ': ' + CkJsonArray__stringAt(arr1,i));
  end;

// The Chilkat JSON path uses ".", "[", and "]" chars for separators.  When a name
// contains one of these chars, use double-quotes in the path:
Memo1.Lines.Add(CkJsonObject__stringOf(json,'"name.with.dots".grain'));

CkJsonObject_Dispose(json);
CkJsonObject_Dispose(obj2);
CkJsonArray_Dispose(arr1);

end;