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======================
Creating Arrow Objects
======================

Recipes related to the creation of Arrays, Tables,
Tensors and all other Arrow entities.

.. contents::

Create Arrays from Standard C++
===============================

Typed subclasses of :cpp:class:`arrow::ArrayBuilder` make it easy
to efficiently create Arrow arrays from existing C++ data:

.. recipe:: ../code/creating_arrow_objects.cc CreatingArrays
  :caption: Creating an array from C++ primitives
  :dedent: 2

.. note::

    Builders will allocate data as needed and insertion should
    have constant amortized time.

Builders can also consume standard C++ containers:

.. recipe:: ../code/creating_arrow_objects.cc CreatingArraysPtr
  :dedent: 2

.. note::
    
    Builders will not take ownership of data in containers and will make a
    copy of the underlying data.

.. _Generate Random Data Example:

Generate Random Data for a Given Schema
=======================================

To generate random data for a given schema, implementing a type visitor is a
good idea. The following example only implements double arrays and list arrays,
but could be easily extended to all types.


.. literalinclude:: ../code/creating_arrow_objects.cc
   :language: cpp
   :linenos:
   :start-at: class RandomBatchGenerator
   :end-at: };  // RandomBatchGenerator
   :caption: Using visitor pattern to generate random record batches
  
Given such a generator, you can create random test data for any supported schema:

.. recipe:: ../code/creating_arrow_objects.cc GenerateRandomData
   :dedent: 2