How Can a Recursive Function Build a Multidimensional Array from Flat Database Results?

Generating a Multidimensional Array from Database Results Using Recursive Function

To generate a nested array representing hierarchical data like pages or categories, a recursive function is often employed. The goal is to take a flat array of database records and transform it into a structured array reflecting the parent-child relationships.

Recursive Function for Tree Building

The following function, buildTree, achieves this task:

def buildTree(elements, parentId=0):
    branch = []
    for element in elements:
        if element['parent_id'] == parentId:
            children = buildTree(elements, element['id'])
            if children:
                element['children'] = children
            branch.append(element)
    return branch

How It Works

1. Initialize Branch: For a given parent ID, create an empty branch list to hold child elements.
2. Iterate Over Elements: Loop through all elements in the flat array.
3. Identify Children: If an element's parent_id matches the current parent ID, it's a child of the branch.
4. Recurse for Children: Call the function recursively for the identified child, finding its sub-children.
5. Add to Branch: Append the child element with its sub-children (if any) to the branch list.
6. Return Branch: Once all children are processed, return the populated branch list.

Example Usage

To process your database records into a hierarchical tree, use:

tree = buildTree(database_result)

The tree variable will now contain a nested array representing the hierarchical structure of pages or categories.

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