(Perl) Using Pre-defined JSON Templates

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.

Chilkat Perl Downloads Perl Module for Windows, MacOS, Linux, Alpine Linux, Solaris

use chilkat();

# One way to create JSON is to do it in a straightforward manner:
$json = chilkat::CkJsonObject->new();
$json->put_EmitCompact(0);
$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() . "\r\n";

# 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->new();
$jsonTemplate->UpdateString("id","{$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->new();
$jsonDonut->put_EmitCompact(0);
$jsonDonut->LoadPredefined("donut");
print $jsonDonut->emit() . "\r\n";

# 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->new();
$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 = 1;
print $jsonDonut->emitWithSubs($donutValues,$omitEmpty) . "\r\n";

# 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) . "\r\n";

# 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
# 	  }
# 	}