(MFC) 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" }

	
}

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkJsonObject.h>
#include <CkJsonArray.h>

void ChilkatSample(void)
    {
    CkString strOut;

    CkJsonObject json;
    json.put_EmitCompact(false);

    // Assume the file contains the data as shown above..
    bool success = json.LoadFile("qa_data/json/pathSample.json");
    if (success != true) {
        strOut.append(json.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // First, let's get the value of "cc1"
    // The path to this value is: nestedObject.aaa.bb1.cc1
    strOut.append(json.stringOf("nestedObject.aaa.bb1.cc1"));
    strOut.append("\r\n");

    // Now let's get number 18 from the nestedArray.
    // It is located at nestedArray[1][2][1]
    // (remember: Indexing is 0-based)
    strOut.append("This should be 18: ");
    strOut.appendInt(json.IntOf("nestedArray[1][2][1]"));
    strOut.append("\r\n");

    // 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.)
    json.put_I(1);
    json.put_J(2);
    json.put_K(1);
    strOut.append("This should be 18: ");
    strOut.appendInt(json.IntOf("nestedArray[i][j][k]"));
    strOut.append("\r\n");

    // Let's iterate over the array containing the numbers 17, 18, 19, 20.
    // First, use the SizeOfArray method to get the array size:
    int sz = json.SizeOfArray("nestedArray[1][2]");
    // The size should be 4.
    strOut.append("size of array = ");
    strOut.appendInt(sz);
    strOut.append(" (should equal 4)");
    strOut.append("\r\n");

    // Now iterate...
    int i;
    for (i = 0; i <= sz - 1; i++) {
        json.put_I(i);
        strOut.appendInt(json.IntOf("nestedArray[1][2][i]"));
        strOut.append("\r\n");
    }

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

    // szI should equal 1.
    int szI = json.SizeOfArray("nestedArray");
    for (i = 0; i <= szI - 1; i++) {
        json.put_I(i);

        int szJ = json.SizeOfArray("nestedArray[i]");
        for (j = 0; j <= szJ - 1; j++) {
            json.put_J(j);

            int szK = json.SizeOfArray("nestedArray[i][j]");
            for (k = 0; k <= szK - 1; k++) {
                json.put_K(k);

                strOut.appendInt(json.IntOf("nestedArray[i][j][k]"));
                strOut.append("\r\n");
            }

        }

    }

    // 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"
    strOut.append(json.stringOf("mixture.arrayA[2].fruit"));
    strOut.append("\r\n");

    // This line of code gets the color "yellow"
    strOut.append(json.stringOf("mixture.arrayA[1].colors[0]"));
    strOut.append("\r\n");

    // Getting an object at a path:
    // This gets the 2nd object in "arrayA"
    CkJsonObject *obj2 = json.ObjectOf("mixture.arrayA[1]");
    // This object's "animal" should be "plankton"
    strOut.append(obj2->stringOf("animal"));
    strOut.append("\r\n");

    // Note that paths are relative to the object, not the absolute root of the JSON document.
    // Starting from obj2, "purple" is at "colors[2]"
    strOut.append(obj2->stringOf("colors[2]"));
    strOut.append("\r\n");

    delete obj2;

    // Getting an array at a path:
    // This gets the array containing the colors red, green, blue:
    CkJsonArray *arr1 = json.ArrayOf("mixture.arrayA[0].colors");
    int szArr1 = arr1->get_Size();
    for (i = 0; i <= szArr1 - 1; i++) {
        strOut.appendInt(i);
        strOut.append(": ");
        strOut.append(arr1->stringAt(i));
        strOut.append("\r\n");
    }

    delete arr1;

    // The Chilkat JSON path uses ".", "[", and "]" chars for separators.  When a name
    // contains one of these chars, use double-quotes in the path:
    strOut.append(json.stringOf("\"name.with.dots\".grain"));
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }