(Visual FoxPro) 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 ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loJson
LOCAL lnSuccess
LOCAL lnSz
LOCAL i
LOCAL j
LOCAL k
LOCAL lnSzI
LOCAL lnSzJ
LOCAL lnSzK
LOCAL loObj2
LOCAL loArr1
LOCAL lnSzArr1

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJson = CreateObject('Chilkat.JsonObject')
loJson.EmitCompact = 0

* Assume the file contains the data as shown above..
lnSuccess = loJson.LoadFile("qa_data/json/pathSample.json")
IF (lnSuccess <> 1) THEN
    ? loJson.LastErrorText
    RELEASE loJson
    CANCEL
ENDIF

* First, let's get the value of "cc1"
* The path to this value is: nestedObject.aaa.bb1.cc1
? loJson.StringOf("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)
? "This should be 18: " + STR(loJson.IntOf("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.)
loJson.I = 1
loJson.J = 2
loJson.K = 1
? "This should be 18: " + STR(loJson.IntOf("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:
lnSz = loJson.SizeOfArray("nestedArray[1][2]")
* The size should be 4.
? "size of array = " + STR(lnSz) + " (should equal 4)"

* Now iterate...

FOR i = 0 TO lnSz - 1
    loJson.I = i
    ? STR(loJson.IntOf("nestedArray[1][2][i]"))
NEXT

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

* szI should equal 1.
lnSzI = loJson.SizeOfArray("nestedArray")
FOR i = 0 TO lnSzI - 1
    loJson.I = i

    lnSzJ = loJson.SizeOfArray("nestedArray[i]")
    FOR j = 0 TO lnSzJ - 1
        loJson.J = j

        lnSzK = loJson.SizeOfArray("nestedArray[i][j]")
        FOR k = 0 TO lnSzK - 1
            loJson.K = k

            ? STR(loJson.IntOf("nestedArray[i][j][k]"))
        NEXT
    NEXT
NEXT

* 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"
? loJson.StringOf("mixture.arrayA[2].fruit")

* This line of code gets the color "yellow"
? loJson.StringOf("mixture.arrayA[1].colors[0]")

* Getting an object at a path:
* This gets the 2nd object in "arrayA"
loObj2 = loJson.ObjectOf("mixture.arrayA[1]")
* This object's "animal" should be "plankton"
? loObj2.StringOf("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]"
? loObj2.StringOf("colors[2]")

RELEASE loObj2

* Getting an array at a path:
* This gets the array containing the colors red, green, blue:
loArr1 = loJson.ArrayOf("mixture.arrayA[0].colors")
lnSzArr1 = loArr1.Size
FOR i = 0 TO lnSzArr1 - 1
    ? STR(i) + ": " + loArr1.StringAt(i)
NEXT
RELEASE loArr1

* The Chilkat JSON path uses ".", "[", and "]" chars for separators.  When a name
* contains one of these chars, use double-quotes in the path:
? loJson.StringOf('"name.with.dots".grain')

RELEASE loJson