(Objective-C) 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 Objective-C Library Downloads MAC OS X (Cocoa) Libs iOS Libs

#import <CkoJsonObject.h>
#import <CkoHashtable.h>

// One way to create JSON is to do it in a straightforward manner:
CkoJsonObject *json = [[CkoJsonObject alloc] init];
json.EmitCompact = NO;
[json UpdateString: @"id" value: @"0001"];
[json UpdateString: @"type" value: @"donut"];
[json UpdateString: @"name" value: @"Cake"];
[json UpdateString: @"image.url" value: @"images/0001.jpg"];
[json UpdateInt: @"image.width" value: [NSNumber numberWithInt: 200]];
[json UpdateInt: @"image.height" value: [NSNumber numberWithInt: 200]];
[json UpdateString: @"thumbnail.url" value: @"images/thumbnails/0001.jpg"];
[json UpdateInt: @"thumbnail.width" value: [NSNumber numberWithInt: 32]];
[json UpdateInt: @"thumbnail.height" value: [NSNumber numberWithInt: 32]];
NSLog(@"%@",[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:

CkoJsonObject *jsonTemplate = [[CkoJsonObject alloc] init];
[jsonTemplate UpdateString: @"id" value: @"{$id}"];
[jsonTemplate UpdateString: @"type" value: @"donut"];
[jsonTemplate UpdateString: @"name" value: @"{$name}"];
[jsonTemplate UpdateString: @"image.url" value: @"{$imageUrl}"];
// The "i." indicates that it's an integer variable.
[jsonTemplate UpdateString: @"image.width" value: @"{$i.imageWidth}"];
[jsonTemplate UpdateString: @"image.height" value: @"{$i.imageHeight}"];
[jsonTemplate UpdateString: @"thumbnail.url" value: @"{$thumbUrl}"];
[jsonTemplate UpdateString: @"thumbnail.width" value: @"{$i.thumbWidth}"];
[jsonTemplate UpdateString: @"thumbnail.height" value: @"{$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:
CkoJsonObject *jsonDonut = [[CkoJsonObject alloc] init];
jsonDonut.EmitCompact = NO;
[jsonDonut LoadPredefined: @"donut"];
NSLog(@"%@",[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:
CkoHashtable *donutValues = [[CkoHashtable alloc] init];
[donutValues AddStr: @"id" value: @"0001"];
[donutValues AddStr: @"name" value: @"Cake"];
[donutValues AddStr: @"imageUrl" value: @"images/0001.jpg"];
[donutValues AddInt: @"imageWidth" value: [NSNumber numberWithInt: 200]];
[donutValues AddInt: @"imageHeight" value: [NSNumber numberWithInt: 200]];
[donutValues AddStr: @"thumbUrl" value: @"images/thumbnails/0001.jpg"];
[donutValues AddInt: @"thumbWidth" value: [NSNumber numberWithInt: 32]];
[donutValues AddInt: @"thumbHeight" value: [NSNumber numberWithInt: 32]];

// Emit with variable substitutions:
BOOL omitEmpty = YES;
NSLog(@"%@",[jsonDonut EmitWithSubs: donutValues omitEmpty: 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" value: @"0002"];
[donutValues AddStr: @"imageUrl" value: @"images/0002.jpg"];
[donutValues AddStr: @"thumbUrl" value: @"images/thumbnails/0002.jpg"];

NSLog(@"%@",[jsonDonut EmitWithSubs: donutValues omitEmpty: 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
// 	  }
// 	}