C

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.

C

#include <C_CkJsonObject.h>
#include <C_CkHashtable.h>

void ChilkatSample(void)
    {
    HCkJsonObject json;
    HCkJsonObject jsonTemplate;
    HCkJsonObject jsonDonut;
    HCkHashtable donutValues;
    BOOL omitEmpty;

    //  One way to create JSON is to do it in a straightforward manner:
    json = CkJsonObject_Create();
    CkJsonObject_putEmitCompact(json,FALSE);
    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);
    printf("%s\n",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:

    jsonTemplate = CkJsonObject_Create();
    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:
    jsonDonut = CkJsonObject_Create();
    CkJsonObject_putEmitCompact(jsonDonut,FALSE);
    CkJsonObject_LoadPredefined(jsonDonut,"donut");
    printf("%s\n",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:
    donutValues = CkHashtable_Create();
    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:
    omitEmpty = TRUE;
    printf("%s\n",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");

    printf("%s\n",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
    //  	  }
    //  	}


    CkJsonObject_Dispose(json);
    CkJsonObject_Dispose(jsonTemplate);
    CkJsonObject_Dispose(jsonDonut);
    CkHashtable_Dispose(donutValues);

    }