Replace function in a child theme

Question

Is there a way to replace a function by another function in a child theme? In other words, in a theme there is a function named "theme_function" and this function is called by several files inside the theme.
I would like to find, if exist, an action that replace all occurrences of "theme_function" with another function "child_function" inside the child theme. Please note that "theme_function" that I want to replace do not have the following block:

if ( !function_exists('theme_function') ) :  

because if it that case is easy to replace the theme_function with another function having the same name in functions.php

Answer 1

If the parent-Theme function in question isn't either pluggable (i.e. wrapped in a if( ! function_exists( $function ) ) conditional) or filterable (i.e. returns its output wrapped in a apply_filters( $filtername, $output )), then there's no easy way to override the function.

You'll have to do one of the following:

1. Replace all template files that contain instances of the function call, and replace those calls with your own child-Theme function, in all such templates
2. Modify the parent Theme, to delete (or make pluggable) the function in question