2.1.3.3. JsonCompositeNode

Contains the data model for a non-leaf JSON tree node.

Background

Pyfx models a JSON as a tree and the leaf of the tree represents the values inside the JSON data. For example,

1[
2   {
3     "Name": "John",
4     "Age": 18
5   }
6]

Both values (John and 18) are leaf nodes, while all the other parenthesis are non-leaf nodes.

Different from JSONSimpleNode, a non-leaf node does not represents any real JSON data, instead it can be seen as a virtual node that is created for tree traversing and to represent the UI edges (e.g. ‘{’ and ‘}’).

There are two separate components to represent a non-leaf node, namely JSONCompositeNode and JSONCompositeEndNode.

  • JSONCompositeNode:

    Conceptually, this is the real non-leaf nodes. There are two UI units stored inside this class, an unexpanded widget and a starting widget. While rendering, depending on the current state (whether the node is expanded or not), Pyfx will choose the correct widgets. E.g., see object.object_node.ObjectNode.

  • JSONCompositeEndNode:

    Conceptually, this is a meta node attached to JSONCompositeNode. This class is created with the single purpose of representing the ending edges of the non-leaf nodes and it delegates all the necessary methods to the attached JSONCompositeNode. This is required for tree traversing with random node accessing, so that we can determine the type of the current focused widget, and thus the correct position for picking the right siblings. E.g., see object.object_end_node.ObjectEndNode.

Urwid Widget

Similar to JSONSimpleNode, both components of a non-leaf node creates and caches the UI unit during runtime.

However, to be able to support node expansion and collapsing, there are in total 3 kind widgets cached inside a composite node, representing the unexpanded, starting and ending edges. All of the widgets shares the same structure as JSONWidget. E.g., see object.object_end_widget.ObjectEndWidget.

Classes

JSONCompositeNode(key, value, node_factory)

base node represents a JSON object or array type, also a non-leaf node in the whole parsed tree.