(Swift 3,4,5...) 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.

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func chilkatTest() {
    // One way to create JSON is to do it in a straightforward manner:
    let json = CkoJsonObject()!
    json.emitCompact = false
    json.update("id", value: "0001")
    json.update("type", value: "donut")
    json.update("name", value: "Cake")
    json.update("image.url", value: "images/0001.jpg")
    json.updateInt("image.width", value: 200)
    json.updateInt("image.height", value: 200)
    json.update("thumbnail.url", value: "images/thumbnails/0001.jpg")
    json.updateInt("thumbnail.width", value: 32)
    json.updateInt("thumbnail.height", value: 32)
    print("\(json.emit()!)")

    // 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:

    let jsonTemplate = CkoJsonObject()!
    jsonTemplate.update("id", value: "{$id}")
    jsonTemplate.update("type", value: "donut")
    jsonTemplate.update("name", value: "{$name}")
    jsonTemplate.update("image.url", value: "{$imageUrl}")
    // The "i." indicates that it's an integer variable.
    jsonTemplate.update("image.width", value: "{$i.imageWidth}")
    jsonTemplate.update("image.height", value: "{$i.imageHeight}")
    jsonTemplate.update("thumbnail.url", value: "{$thumbUrl}")
    jsonTemplate.update("thumbnail.width", value: "{$i.thumbWidth}")
    jsonTemplate.update("thumbnail.height", value: "{$i.thumbHeight}")
    // Give this template a name.
    jsonTemplate.predefine("donut")

    // --------------------------------------------------------------------------
    // 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:
    let jsonDonut = CkoJsonObject()!
    jsonDonut.emitCompact = false
    jsonDonut.loadPredefined("donut")
    print("\(jsonDonut.emit()!)")

    // 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:
    let donutValues = CkoHashtable()!
    donutValues.addStr("id", value: "0001")
    donutValues.addStr("name", value: "Cake")
    donutValues.addStr("imageUrl", value: "images/0001.jpg")
    donutValues.addInt("imageWidth", value: 200)
    donutValues.addInt("imageHeight", value: 200)
    donutValues.addStr("thumbUrl", value: "images/thumbnails/0001.jpg")
    donutValues.addInt("thumbWidth", value: 32)
    donutValues.addInt("thumbHeight", value: 32)

    // Emit with variable substitutions:
    var omitEmpty: Bool = true
    print("\(jsonDonut.emit(withSubs: donutValues, omitEmpty: omitEmpty)!)")

    // 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:
    donutValues.addStr("id", value: "0002")
    donutValues.addStr("imageUrl", value: "images/0002.jpg")
    donutValues.addStr("thumbUrl", value: "images/thumbnails/0002.jpg")

    print("\(jsonDonut.emit(withSubs: donutValues, omitEmpty: omitEmpty)!)")

    // 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
    // 	  }
    // 	}

}