InsideQC Forums

Posted: **Mon May 08, 2023 4:23 am**

Json tutorial continued.

Starting with a json string borrowed from https://json.org/example.html

	string json_string_data = "{\"widget\": {\"debug\": \"on\", \"window\": {\"title\": \"Sample Konfabulator Widget\", \"name\": \"main_window\", \"width\": 500, \"height\": 500 }, \"image\": {\"src\": \"Images/Sun.png\", \"name\": \"sun1\", \"hOffset\": 250, \"vOffset\": 250, \"alignment\": \"center\"}, \"text\": {\"data\": \"Click Here\", \"size\": 36, \"style\": \"bold\", \"name\": \"text1\", \"hOffset\": 250, \"vOffset\": 100, \"alignment\": \"center\", \"onMouseUp\": \"sun1.opacity = (sun1.opacity / 100) * 90;\"} }}";

We parse the string into a json node.

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jsonnode root = json_parse(json_string_data);

Next we probably want the data, we grab that using the apropriate json_get_<type> method.
Here we will grab the text size.

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float f_text_size = json_get_float(root.widget.text.size);

If instead of the data, we had just wanted to know what that data was called, we would grab its name

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string nodeName = json_get_name(root.widget.text.size);

If we wanted to iterate over the top level objects of the node, we could use a for loop
over the length, with a child index like so:

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for (int idx = 0; idx < json_get_length(root); idx++)
{
	jsonnode node = json_get_child_at_index(idx);

	string nodeName = json_get_name(node);
}

We loop over array nodes the same way.

If we are parsing json data that we have no previous knowledge of, we will need to query for the data types so we know which json_get_<type>() function to call.

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float data_type = json_get_value_type(node);

Calling that function will result in one of the values from this enum:

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enum json_type_e : int
{
	JSON_TYPE_STRING,
	JSON_TYPE_NUMBER,
	JSON_TYPE_OBJECT,
	JSON_TYPE_ARRAY,
	JSON_TYPE_TRUE,
	JSON_TYPE_FALSE,
	JSON_TYPE_NULL
};

Lastly, when we are done with our jsonnode, we should free it back up with a call to:

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json_free(root);

Posted: **Mon May 08, 2023 4:38 am**

In the previous post we used json_get_float(node) to get a float out of the node.

This can be simplified using some syntactic sugar.
instead of using json_get_float(), we could just append a ".f" to the nodepath as follows:

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float f_text_size = root.widget.text.size.f;

This also works for strings

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string s_window_title = root.widget.window.title.s;

and integers.

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int i_text_size = root.widget.text.size.i;

accessors are also provided for the other functions.

json_get_value_type

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float valueType = root.widget.text.size.type;

json_get_length

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float nodeLength = root.length;

json_get_child_at_index

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jsonnode widgetNode =  root.a[0];

json_find_object_child

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jsonnode widgetNode =  root["widget"];

json_get_name

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float valueType = root.widget.text.size.name;

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