(DataFlex) Using Pre-defined JSON Templates

Demonstrates how to predefine a JSON template, and then use it to emit JSON with variable substitutions.

Note: This example requires Chilkat v9.5.0.67 or greater.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoJson
    Boolean iSuccess
    Handle hoJsonTemplate
Donut    Handle hoJsonDonut
    Variant vDonutValues
    Handle hoDonutValues
    Boolean iOmitEmpty
    String sTemp1

    // One way to create JSON is to do it in a straightforward manner:
    Get Create (RefClass(cComChilkatJsonObject)) To hoJson
    If (Not(IsComObjectCreated(hoJson))) Begin
        Send CreateComObject of hoJson
    End
    Set ComEmitCompact Of hoJson To False
    Get ComUpdateString Of hoJson "id" "0001" To iSuccess
    Get ComUpdateString Of hoJson "type" "donut" To iSuccess
    Get ComUpdateString Of hoJson "name" "Cake" To iSuccess
    Get ComUpdateString Of hoJson "image.url" "images/0001.jpg" To iSuccess
    Get ComUpdateInt Of hoJson "image.width" 200 To iSuccess
    Get ComUpdateInt Of hoJson "image.height" 200 To iSuccess
    Get ComUpdateString Of hoJson "thumbnail.url" "images/thumbnails/0001.jpg" To iSuccess
    Get ComUpdateInt Of hoJson "thumbnail.width" 32 To iSuccess
    Get ComUpdateInt Of hoJson "thumbnail.height" 32 To iSuccess
    Get ComEmit Of hoJson To sTemp1
    Showln sTemp1

    // The JSON created by the above code:

    // 	{ 
    // 	  "id": "0001",
    // 	  "type": "donut",
    // 	  "name": "Cake",
    // 	  "image": { 
    // 	    "url": "images/0001.jpg",
    // 	    "width": 200,
    // 	    "height": 200
    // 	  },
    // 	  "thumbnail": { 
    // 	    "url": "images/thumbnails/0001.jpg",
    // 	    "width": 32,
    // 	    "height": 32
    // 	  }
    // 	}

    // An alternative is to predefine a template, and then use it to emit with variable substitutions.
    // For example:

    Get Create (RefClass(cComChilkatJsonObject)) To hoJsonTemplate
    If (Not(IsComObjectCreated(hoJsonTemplate))) Begin
        Send CreateComObject of hoJsonTemplate
    End
    Get ComUpdateString Of hoJsonTemplate "id" "{$id}" To iSuccess
    Get ComUpdateString Of hoJsonTemplate "type" "donut" To iSuccess
    Get ComUpdateString Of hoJsonTemplate "name" "{$name}" To iSuccess
    Get ComUpdateString Of hoJsonTemplate "image.url" "{$imageUrl}" To iSuccess
    // The "i." indicates that it's an integer variable.
    Get ComUpdateString Of hoJsonTemplate "image.width" "{$i.imageWidth}" To iSuccess
    Get ComUpdateString Of hoJsonTemplate "image.height" "{$i.imageHeight}" To iSuccess
    Get ComUpdateString Of hoJsonTemplate "thumbnail.url" "{$thumbUrl}" To iSuccess
    Get ComUpdateString Of hoJsonTemplate "thumbnail.width" "{$i.thumbWidth}" To iSuccess
    Get ComUpdateString Of hoJsonTemplate "thumbnail.height" "{$i.thumbHeight}" To iSuccess
    // Give this template a name.
    Get ComPredefine Of hoJsonTemplate "donut" To iSuccess

    // --------------------------------------------------------------------------
    // OK, the template is defined.  Defining a template can be done once
    // at the start of your program, and you can discard the jsonTemplate object (it
    // doesn't need to stick around..)

    // Now we can create instances of the JSON object by name:
    Get Create (RefClass(cComChilkatJsonObject)) To hoJsonDonut
    If (Not(IsComObjectCreated(hoJsonDonut))) Begin
        Send CreateComObject of hoJsonDonut
    End
    Set ComEmitCompact Of hoJsonDonut To False
    Get ComLoadPredefined Of hoJsonDonut "donut" To iSuccess
    Get ComEmit Of hoJsonDonut To sTemp1
    Showln sTemp1

    // The output is this:

    // 	{ 
    // 	  "id": "{$id}",
    // 	  "type": "donut",
    // 	  "name": "{$name}",
    // 	  "image": { 
    // 	    "url": "{$imageUrl}",
    // 	    "width": "{$i.imageWidth}",
    // 	    "height": "{$i.imageHeight}"
    // 	  },
    // 	  "thumbnail": { 
    // 	    "url": "{$thumbUrl}",
    // 	    "width": "{$i.thumbWidth}",
    // 	    "height": "{$i.thumbHeight}"
    // 	  }
    // 	}

    // Finally, we can substitute variables like this:
    Get Create (RefClass(cComChilkatHashtable)) To hoDonutValues
    If (Not(IsComObjectCreated(hoDonutValues))) Begin
        Send CreateComObject of hoDonutValues
    End
    Get ComAddStr Of hoDonutValues "id" "0001" To iSuccess
    Get ComAddStr Of hoDonutValues "name" "Cake" To iSuccess
    Get ComAddStr Of hoDonutValues "imageUrl" "images/0001.jpg" To iSuccess
    Get ComAddInt Of hoDonutValues "imageWidth" 200 To iSuccess
    Get ComAddInt Of hoDonutValues "imageHeight" 200 To iSuccess
    Get ComAddStr Of hoDonutValues "thumbUrl" "images/thumbnails/0001.jpg" To iSuccess
    Get ComAddInt Of hoDonutValues "thumbWidth" 32 To iSuccess
    Get ComAddInt Of hoDonutValues "thumbHeight" 32 To iSuccess

    // Emit with variable substitutions:
    Move True To iOmitEmpty
    Get ComEmitWithSubs Of hoJsonDonut     Get pvComObject of hoDonutValues to vDonutValues
vDonutValues iOmitEmpty To sTemp1
    Showln sTemp1

    // Output:

    // 	{ 
    // 	  "id": "0001",
    // 	  "type": "donut",
    // 	  "name": "Cake",
    // 	  "image": { 
    // 	    "url": "images/0001.jpg",
    // 	    "width": 200,
    // 	    "height": 200
    // 	  },
    // 	  "thumbnail": { 
    // 	    "url": "images/thumbnails/0001.jpg",
    // 	    "width": 32,
    // 	    "height": 32
    // 	  }
    // 	}

    // Change some of the values:
    Get ComAddStr Of hoDonutValues "id" "0002" To iSuccess
    Get ComAddStr Of hoDonutValues "imageUrl" "images/0002.jpg" To iSuccess
    Get ComAddStr Of hoDonutValues "thumbUrl" "images/thumbnails/0002.jpg" To iSuccess

    Get ComEmitWithSubs Of hoJsonDonut     Get pvComObject of hoDonutValues to vDonutValues
vDonutValues iOmitEmpty To sTemp1
    Showln sTemp1

    // Output:

    // 	{ 
    // 	  "id": "0002",
    // 	  "type": "donut",
    // 	  "name": "Cake",
    // 	  "image": { 
    // 	    "url": "images/0002.jpg",
    // 	    "width": 200,
    // 	    "height": 200
    // 	  },
    // 	  "thumbnail": { 
    // 	    "url": "images/thumbnails/0002.jpg",
    // 	    "width": 32,
    // 	    "height": 32
    // 	  }
    // 	}


End_Procedure