CakePHP 3 Passing Alphanumeric Parameter To Resource Routes - cakephp-3.0

Question

I'm trying to pass parameter in resource route. My routes.php has:
$routes->resources('Products', [
'map' => [
'sku/:sku' => [
'action' => 'viewBySku',
'method' => 'GET',
]
]
]);
});
And my control action is as follows:
public function viewBySku($sku) {
die($sku);
}
After I execute the route the controller is generating a warning:
Missing argument 1 for viewBySku()
What am I missing?
Edit:
I want to use alphanumeric value for the parameter. Most answers I've found are explaining how to pass integers only.

Answer 1

So here is what I've ended up doing:
routes.php
$routes->resources('Products', [
'map' => [
'sku/:sku' => [
'action' => 'viewBySku',
'method' => 'GET',
]
]
]);
controller
public function viewBySku() {
if (!$sku = $this->request->param('sku')) {
throw new BadRequestException("Sku is missing");
}
die($sku);
}
Apparently, my variable is being passed to router but not to the controller's action.
Other Solution
So after looking into resource routes I've found out that you can pass connect options to it:
$routes->resources('Products', [
'map' => [
'sku/:sku' => [
'action' => 'viewBySku',
'method' => 'GET',
]
],
'connectOptions' => [
'sku' => '[a-zA-Z0-9\-]{2,10}',
'pass' => ['sku', 'id']
]
]);
You can also modify the id's regex if you want to pass alphanumeric values to id parameter:
$routes->resources('Products', [
'connectOptions' => [
'id' => '[a-zA-Z0-9\-]{2,10}'
]
]);