CkPython

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.

CkPython

import chilkat

# One way to create JSON is to do it in a straightforward manner:
json = chilkat.CkJsonObject()
json.put_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)
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:

jsonTemplate = chilkat.CkJsonObject()
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:
jsonDonut = chilkat.CkJsonObject()
jsonDonut.put_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:
donutValues = chilkat.CkHashtable()
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:
omitEmpty = True
print(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")

print(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
# 	  }
# 	}