Xojo Plugin

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.

Xojo Plugin

// One way to create JSON is to do it in a straightforward manner:
Dim json As New Chilkat.JsonObject
json.EmitCompact = False
Dim success As Boolean
success = json.UpdateString("id","0001")
success = json.UpdateString("type","donut")
success = json.UpdateString("name","Cake")
success = json.UpdateString("image.url","images/0001.jpg")
success = json.UpdateInt("image.width",200)
success = json.UpdateInt("image.height",200)
success = json.UpdateString("thumbnail.url","images/thumbnails/0001.jpg")
success = json.UpdateInt("thumbnail.width",32)
success = json.UpdateInt("thumbnail.height",32)
System.DebugLog(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
success = jsonTemplate.UpdateString("id","{$id}")
success = jsonTemplate.UpdateString("type","donut")
success = jsonTemplate.UpdateString("name","{$name}")
success = jsonTemplate.UpdateString("image.url","{$imageUrl}")
// The "i." indicates that it's an integer variable.
success = jsonTemplate.UpdateString("image.width","{$i.imageWidth}")
success = jsonTemplate.UpdateString("image.height","{$i.imageHeight}")
success = jsonTemplate.UpdateString("thumbnail.url","{$thumbUrl}")
success = jsonTemplate.UpdateString("thumbnail.width","{$i.thumbWidth}")
success = jsonTemplate.UpdateString("thumbnail.height","{$i.thumbHeight}")
// Give this template a name.
success = 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
success = jsonDonut.LoadPredefined("donut")
System.DebugLog(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
success = donutValues.AddStr("id","0001")
success = donutValues.AddStr("name","Cake")
success = donutValues.AddStr("imageUrl","images/0001.jpg")
success = donutValues.AddInt("imageWidth",200)
success = donutValues.AddInt("imageHeight",200)
success = donutValues.AddStr("thumbUrl","images/thumbnails/0001.jpg")
success = donutValues.AddInt("thumbWidth",32)
success = donutValues.AddInt("thumbHeight",32)

// Emit with variable substitutions:
Dim omitEmpty As Boolean
omitEmpty = True
System.DebugLog(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:
success = donutValues.AddStr("id","0002")
success = donutValues.AddStr("imageUrl","images/0002.jpg")
success = donutValues.AddStr("thumbUrl","images/thumbnails/0002.jpg")

System.DebugLog(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
// 	  }
// 	}