iterate an cJSON nested object in c

Question

How to iterate nested cJSON object? i want to get(print) all keys and values from deviceData parent object in C. Its a cJson object.

 obj =     {      "command": "REPLACE_ROWS",
            "table": "Device.XXX",
            "deviceData": {
                    "device0": {
                      "DeviceName": "Filtered Device",
                        "MACAddress": "112233445599"
                    },
                    "device1": {
                        "DeviceName": "Filtered Device",
                        "MACAddress": "112233445599"
                    },
                    "device2": {
                        "DeviceName": "Filtered Device",
                        "MACAddress": "112233445599"
                    }
           }
    };

how to print keys of deviceData (ex device0 device1 device 2 and so on) in C. Thanks in advance.

What have you tried so far? What problems do you have with your code? How does, or doesn't it work? Can you please try to create a [Minimal, Complete, and Verifiable Example](http://stackoverflow.com/help/mcve) and show us? And if you haven't done so yeyt, please [read about how to ask good questions](http://stackoverflow.com/help/how-to-ask). — Some programmer dude, Jan 19 '16 at 12:20
@Jochimpileborg :Thanks for your comment.Will post clear questions next time. — selvam, Jan 29 '16 at 06:45

score 12 · Accepted Answer · answered Jan 19 '16 at 12:32

12

Supposing obj is a string containing your object, you parse it then use next to iterate:

cJSON * root = cJSON_Parse(obj);
cJSON * deviceData = cJSON_GetObjectItem(root,"deviceData");
if( deviceData ) {
   cJSON *device = deviceData->child;
   while( device ) {
      // get and print key
      device = device->next;
   }
}

answered Jan 19 '16 at 12:32

Ilya

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Thanks a lot it worked. In while loop i printed key using printf("Key is %s",device->string); – selvam Jan 29 '16 at 07:01

score 1 · Answer 2 · answered Feb 02 '18 at 12:53

1

There's a comment in the cJSON documentation about iterating over an object:

To iterate over an object, you can use the cJSON_ArrayForEach macro the same way as for arrays.

See: https://github.com/DaveGamble/cJSON#objects

The cJSON_ArrayForEach macro basically does the same as ilya's proposal, but it avoids relying on cJSON implementation details.

answered Feb 02 '18 at 12:53

Jonatan

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About the implementation detail: I try to not break API and ABI, this means that this will work for 1.x.x versions indefinitely without `cJSON_ArrayForEach`. The cJSON struct in v2 will change for sure, but `next` and `child` will probably stay the same. (I'm the maintainer of cJSON). – FSMaxB Feb 02 '18 at 16:46

iterate an cJSON nested object in c

2 Answers2