VB.NET

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.

VB.NET

' One way to create JSON is to do it in a straightforward manner:
Dim json As New Chilkat.JsonObject
json.EmitCompact = False
json.UpdateString("id","0001")
json.UpdateString("type","donut")
json.UpdateString("name","Cake")
json.UpdateString("image.url","images/0001.jpg")
json.UpdateInt("image.width",200)
json.UpdateInt("image.height",200)
json.UpdateString("thumbnail.url","images/thumbnails/0001.jpg")
json.UpdateInt("thumbnail.width",32)
json.UpdateInt("thumbnail.height",32)
Debug.WriteLine(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:

Dim jsonTemplate As New Chilkat.JsonObject
jsonTemplate.UpdateString("id","{$id}")
jsonTemplate.UpdateString("type","donut")
jsonTemplate.UpdateString("name","{$name}")
jsonTemplate.UpdateString("image.url","{$imageUrl}")
' The "i." indicates that it's an integer variable.
jsonTemplate.UpdateString("image.width","{$i.imageWidth}")
jsonTemplate.UpdateString("image.height","{$i.imageHeight}")
jsonTemplate.UpdateString("thumbnail.url","{$thumbUrl}")
jsonTemplate.UpdateString("thumbnail.width","{$i.thumbWidth}")
jsonTemplate.UpdateString("thumbnail.height","{$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:
Dim jsonDonut As New Chilkat.JsonObject
jsonDonut.EmitCompact = False
jsonDonut.LoadPredefined("donut")
Debug.WriteLine(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:
Dim donutValues As New Chilkat.Hashtable
donutValues.AddStr("id","0001")
donutValues.AddStr("name","Cake")
donutValues.AddStr("imageUrl","images/0001.jpg")
donutValues.AddInt("imageWidth",200)
donutValues.AddInt("imageHeight",200)
donutValues.AddStr("thumbUrl","images/thumbnails/0001.jpg")
donutValues.AddInt("thumbWidth",32)
donutValues.AddInt("thumbHeight",32)

' Emit with variable substitutions:
Dim omitEmpty As Boolean = True
Debug.WriteLine(jsonDonut.EmitWithSubs(donutValues,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","0002")
donutValues.AddStr("imageUrl","images/0002.jpg")
donutValues.AddStr("thumbUrl","images/thumbnails/0002.jpg")

Debug.WriteLine(jsonDonut.EmitWithSubs(donutValues,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
' 	  }
' 	}