Removing elements from a JSON object

[andysCaplin]

Hi, I'm creating a JSON object to hold a list of subjects each of which has an associated list of fields - the object ends up looking like shown below

{
  "objects": {
    "/SYSTEM/USER": {
      "fields": {
        "ServiceState": "UP"
      }
    },
    "/SYSTEM/INFO": {
      "fields": {
        "SourceID": "0"
      }
    }
  }
}

I create the elements using the [] notation

status_page.["objects"][subject]["fields"][name] = value;

I want to be able to delete an object with a given subject - e.g. the entry for "/SYSTEM/USER". There doesn't seem to be an equivalent notation to completely delete it. I tried

status_page.["objects"][subject] = NULL;

That sets the contents to 0 but leaves the element for the subject in.

I tried using json_pointer::remove() but it expects '/' as a separator, but my subjects already have '/'s - i.e. I can't use "objects//SYSTEM/USER".

Is there any way of achieving this without turning it into an array and using the method you described in #289 ?

[danielaparker]

To remove with a JSON Pointer, all occurrences of ~ and / in the member name must be escaped with ~0 and ~1 respectively, so you'd need to use

json val = json::parse(data);
jsonpointer::remove(val, "/objects/~1SYSTEM~1USER");

Alternatively, you could use the json_pointer class to do the escaping for you,

jsonpointer::json_pointer ptr;
ptr /= "objects";
ptr /= "/SYSTEM/USER";
jsonpointer::remove(val, ptr);

But the simplest way would be to use

val["objects"].erase("/SYSTEM/USER");

[andysCaplin]

Thank you. That worked perfectly - I used the erase.