Eager Loading 是否区分大小写？

Question

Taking in consideration the documentation https://laravel.com/docs/5.0/eloquent#eager-loading lets have the following example:

$clients = Clients::with('Addresses')->get();

We can now loop addresses like:

foreach ($clients->Addresses ..) 

foreach ($clients->addresses ..) 

If we use the first approach (with case-sensitive) does that mean that the Eager Loading results will be ignored and another query will be done or not?

As you know, If we do something like:

$clients = Clients::get();

We are still able to loop through the addresses but another query will be taking place.

foreach ($clients->Addresses ..)

Answer 1

From some quick tests, it seems that while Eager Loaded is in fact case-insensitive, it is only so when using the same case while loading and while accessing. For your example:

$clients = Client::with(['addresses' => function ($q) {
  $q->limit(2);
}])->get();

// Good
foreach ($clients as $client){
  foreach ($client->addresses as $address) {
    // Should loop twice and output 2 Addresses
  }
}

// Bad
foreach ($clients as $client){
  foreach ($client->Addresses as $address) {
    // Will loop X times for each associated `address`
  }
}

The use of DB::enableQueryLog() and DB::getQueryLog() can assist with debugging. If you're eager loading, you should see a row:

"query" => "select * from `addresses` where `addresses`.`client_id` in (...) limit 1

If an additional query is being run while iterating, you'll see a query for each Client:

"query" => "select * from `addresses` where `addresses`.`client_id` = ? and `addresses`.`client_id` is not null",

There are a multitude of other methods to test this, but the long and short of it is that accessing $client->addresses and $client->Addresses does in fact produce different outcomes, even if they seem similar. Use the same case for loading that you use while accessing and you'll be good. Note that since relationships are functions, using the correct case for PHP functions ( studlyCaps aka pascalCase ) should be your go-to approach.