Xbase++

Using Pre-defined JSON Templates

See more JSON Examples

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.

Xbase++

LOCAL oJson
LOCAL oJsonTemplate
LOCAL oJsonDonut
LOCAL oDonutValues
LOCAL nOmitEmpty

//  One way to create JSON is to do it in a straightforward manner:
oJson := CreateObject("Chilkat.JsonObject")
oJson:EmitCompact := 0
oJson:UpdateString("id", "0001")
oJson:UpdateString("type", "donut")
oJson:UpdateString("name", "Cake")
oJson:UpdateString("image.url", "images/0001.jpg")
oJson:UpdateInt("image.width", 200)
oJson:UpdateInt("image.height", 200)
oJson:UpdateString("thumbnail.url", "images/thumbnails/0001.jpg")
oJson:UpdateInt("thumbnail.width", 32)
oJson:UpdateInt("thumbnail.height", 32)
? oJson: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:

oJsonTemplate := CreateObject("Chilkat.JsonObject")
oJsonTemplate:UpdateString("id", "{$id}")
oJsonTemplate:UpdateString("type", "donut")
oJsonTemplate:UpdateString("name", "{$name}")
oJsonTemplate:UpdateString("image.url", "{$imageUrl}")
//  The "i." indicates that it's an integer variable.
oJsonTemplate:UpdateString("image.width", "{$i.imageWidth}")
oJsonTemplate:UpdateString("image.height", "{$i.imageHeight}")
oJsonTemplate:UpdateString("thumbnail.url", "{$thumbUrl}")
oJsonTemplate:UpdateString("thumbnail.width", "{$i.thumbWidth}")
oJsonTemplate:UpdateString("thumbnail.height", "{$i.thumbHeight}")
//  Give this template a name.
oJsonTemplate: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:
oJsonDonut := CreateObject("Chilkat.JsonObject")
oJsonDonut:EmitCompact := 0
oJsonDonut:LoadPredefined("donut")
? oJsonDonut: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:
oDonutValues := CreateObject("Chilkat.Hashtable")
oDonutValues:AddStr("id", "0001")
oDonutValues:AddStr("name", "Cake")
oDonutValues:AddStr("imageUrl", "images/0001.jpg")
oDonutValues:AddInt("imageWidth", 200)
oDonutValues:AddInt("imageHeight", 200)
oDonutValues:AddStr("thumbUrl", "images/thumbnails/0001.jpg")
oDonutValues:AddInt("thumbWidth", 32)
oDonutValues:AddInt("thumbHeight", 32)

//  Emit with variable substitutions:
nOmitEmpty := 1
? oJsonDonut:EmitWithSubs(oDonutValues, nOmitEmpty)

//  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:
oDonutValues:AddStr("id", "0002")
oDonutValues:AddStr("imageUrl", "images/0002.jpg")
oDonutValues:AddStr("thumbUrl", "images/thumbnails/0002.jpg")

? oJsonDonut:EmitWithSubs(oDonutValues, nOmitEmpty)

//  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
//  	  }
//  	}

oJson:destroy()
oJsonTemplate:destroy()
oJsonDonut:destroy()
oDonutValues:destroy()