Eager loading relations with conditions on declaration

[Lloople]

• Laravel Version: 5.6.18
• PHP Version: 7.2.2
• Database Driver & Version: MySQL 5.7.19

Description:

I try to load a nested relationship which contains a where clause on declaration using model's attributes. Since this models are not instantiated yet, the value of the property is null because it's not pulled from DB yet.

Steps To Reproduce:

// App\Models\Page.php

public function contents()
{
    return $this->hasMany(PageContent::class, 'target_id');
}

// App\Models\PageContent.php

public function route()
{
    return $this->belongsTo(Route::class, 'target_id', 'target_id')
        ->where('language', $this->language);
}

// routes/web.php

Route::get('test', function () {
    $page = \Origin\Models\Page::with('contents.route')->find(1);
    dd($page->contents->first()->route); // null
});

Route::get('test-with-results', function () {
    $page = \Origin\Models\Page::with('contents')->find(1);
    dd($page->contents->first()->route); // Route model
});

The query performed with the eager loading is

select * from `routes` where `language` is null and `routes`.`target_id` in ('1')

because at the time of eager loading the nested relation routes, the contents models hasn't been instantiated first.

I tried with

->whereRaw('language', 'pages_content'.language')

but didn't work either.

Very appreciated for a solution to this or an alternative if it's not possible at the moment.

Thank you very much.

[staudenmeir]

Since you only have one Page, you can do this:

$page = \Origin\Models\Page::find(1);
$page->contents->load('route');

[Lloople]

@staudenmeir thank tou for your Solution.

But maybe I’ll get the other case in the future, listing pages for example. Maybe this will work?

$pages->load('contents.route');

[staudenmeir]

That will give you the same problem as with('contents.route').

Eager loading is not possible with a constraint like this. Image how the query would have to look:

select * from `routes`
where (`routes`.`target_id` = `1` and `language` = 'a')
    or (`routes`.`target_id` = `2` and `language` = 'b')
    ....

You can use a JOIN for cases like that.