Tcl

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.

Tcl

load ./chilkat.dll

# One way to create JSON is to do it in a straightforward manner:
set json [new_CkJsonObject]

CkJsonObject_put_EmitCompact $json 0
CkJsonObject_UpdateString $json "id" "0001"
CkJsonObject_UpdateString $json "type" "donut"
CkJsonObject_UpdateString $json "name" "Cake"
CkJsonObject_UpdateString $json "image.url" "images/0001.jpg"
CkJsonObject_UpdateInt $json "image.width" 200
CkJsonObject_UpdateInt $json "image.height" 200
CkJsonObject_UpdateString $json "thumbnail.url" "images/thumbnails/0001.jpg"
CkJsonObject_UpdateInt $json "thumbnail.width" 32
CkJsonObject_UpdateInt $json "thumbnail.height" 32
puts [CkJsonObject_emit $json]

# 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:

set jsonTemplate [new_CkJsonObject]

CkJsonObject_UpdateString $jsonTemplate "id" "{$id}"
CkJsonObject_UpdateString $jsonTemplate "type" "donut"
CkJsonObject_UpdateString $jsonTemplate "name" "{$name}"
CkJsonObject_UpdateString $jsonTemplate "image.url" "{$imageUrl}"
# The "i." indicates that it's an integer variable.
CkJsonObject_UpdateString $jsonTemplate "image.width" "{$i.imageWidth}"
CkJsonObject_UpdateString $jsonTemplate "image.height" "{$i.imageHeight}"
CkJsonObject_UpdateString $jsonTemplate "thumbnail.url" "{$thumbUrl}"
CkJsonObject_UpdateString $jsonTemplate "thumbnail.width" "{$i.thumbWidth}"
CkJsonObject_UpdateString $jsonTemplate "thumbnail.height" "{$i.thumbHeight}"
# Give this template a name.
CkJsonObject_Predefine $jsonTemplate "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:
set jsonDonut [new_CkJsonObject]

CkJsonObject_put_EmitCompact $jsonDonut 0
CkJsonObject_LoadPredefined $jsonDonut "donut"
puts [CkJsonObject_emit $jsonDonut]

# 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:
set donutValues [new_CkHashtable]

CkHashtable_AddStr $donutValues "id" "0001"
CkHashtable_AddStr $donutValues "name" "Cake"
CkHashtable_AddStr $donutValues "imageUrl" "images/0001.jpg"
CkHashtable_AddInt $donutValues "imageWidth" 200
CkHashtable_AddInt $donutValues "imageHeight" 200
CkHashtable_AddStr $donutValues "thumbUrl" "images/thumbnails/0001.jpg"
CkHashtable_AddInt $donutValues "thumbWidth" 32
CkHashtable_AddInt $donutValues "thumbHeight" 32

# Emit with variable substitutions:
set omitEmpty 1
puts [CkJsonObject_emitWithSubs $jsonDonut $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:
CkHashtable_AddStr $donutValues "id" "0002"
CkHashtable_AddStr $donutValues "imageUrl" "images/0002.jpg"
CkHashtable_AddStr $donutValues "thumbUrl" "images/thumbnails/0002.jpg"

puts [CkJsonObject_emitWithSubs $jsonDonut $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
# 	  }
# 	}

delete_CkJsonObject $json
delete_CkJsonObject $jsonTemplate
delete_CkJsonObject $jsonDonut
delete_CkHashtable $donutValues