How to call a function of one module in another module

Question

How can I call a function of one module in another module? I want to call uc_stock_adjust() function of uc_stock.module in my own custom module. Is it possible?

Here is my code so far:

function my_module_node_presave($node){ 
  if($node->type == 'add_stock') { 
    $stock_value = $node->field_stock_value['und'][0]['value']; 
    $sku = $node->field_sku['und'][0]['value']; 
    if (module_exists('uc_stock') && function_exists('uc_stock_adjust')) {
      uc_stock_adjust($sku, $stock_value); 
    } 
  } 
}   

I want to add and delete stock of products by using reference uc_stock_adjust(), which is defined in uc_stock.module, in my custom module. But when I try the above code, it doesn't work.

It giving an error, and the error is:

Notice: Undefined variable: sku in my_module_node_presave() (line 29 of \sites\all\modules\my_module\my_module.module)‌​

Answer 1

To call the function of one module in another module:

1. If the function is not in the .module file, call module_load_include()

   //Load node.admin.inc from the node module
   module_load_include('inc', 'node', 'node.admin');
   

2. Call the function from the other module

   function_you_want_to_call();
   

Answer 2

Undefined variable: sku means that you have not declared a value for the variable $sku. Have you done debugging to make sure that $node->field_sku['und'][0]['value'] outputs a value?

Answer 3

See module_invoke(). This calls a function (hook) in a specified module.

The given hook uc_stock_adjust() can thus be called by: module_invoke('uc_stock', 'adjust');. (Note that this is because the function follows Drupal conventions of module_name_function_name).

If desired additional arguments can also be passed to a function's parameters with: module_invoke('uc_stock', 'adjust', $first_param_to_pass, $second_param_to_pass, $etc);