Laravel Multiple requirements for relationship - php

Question

I have an Item table, Meta table and a Item_Meta table which has all meta records for Items. One Item has many Meta records.
Item_meta has the following columns:
Item_id | Meta_id | Value
Lets say I have a requirements:
Requirement 1 - ['Meta_id' => 1, 'value' => 'new']
Requirement 2 - ['Meta_id' => 3, 'value' => 'LCD']
I need to build a query get all items, which have meta_id with id 1 equal to new, and meta_id with id 3 equal to LCD.
So if an item does not have one of this metas (or one of metas has wrong value) it should not be returned.

Answer 1

You can filter your models on relation's attributes using Eloquent's whereHas() method. In your case the following code should do the trick:
$items = Item::whereHas('metas', function($query) {
$query->where('Meta_id', 1);
$query->where('value', 'new);
})
->whereHas('metas', function($query) {
$query->where('Meta_id', 3);
$query->where('value', 'LCD);
})
->get();
I assumed that your item->meta relation is called metas.
You could also use another form of using whereHas() where you provide number of matching related records. The code will be a bit more complex but it will result in less subselects in the executed query:
$items = Item::whereHas('metas', function($query) {
$query->where('Meta_id', 1);
$query->where('value', 'new);
$query->orWhere(function($query2) {
$query2->where('Meta_id', 3);
$query2->where('value', 'LCD);
};
}, '=', 2)
->get();

Answer 2

I have tried the first approach from the previous answer before asking the question, but it failed so I thought it had a mistake. But after seeing and that answer it seemed that I don't understand something. So I digged inside of Laravel Eloquent internals and here is what I found:
Eloquent Build class "::where" method changes $this->query property before returning the instance. Here is the code:
public function where($column, $operator = null, $value = null, $boolean = 'and')
{
if ($column instanceof Closure) {
$query = $this->model->newQueryWithoutScopes();
call_user_func($column, $query);
$this->query->addNestedWhereQuery($query->getQuery(), $boolean);
} else {
call_user_func_array([$this->query, 'where'], func_get_args());
}
return $this;
}
Take notice of "$this->query->addNestedWhereQuery($query->getQuery(), $boolean);" on the 6th line.
The Builder class "::whereHas" method does not modify "$this->query" property.
public function whereHas($relation, Closure $callback, $operator = '>=', $count = 1)
{
return $this->has($relation, $operator, $count, 'and', $callback);
}
So, what it has to do with my problem. I have created a query like this:
$query = Item::where('active',1);
Then I added the conditions:
if($meta){
$query->whereHas('metas', function($query) {
$query->where('Meta_id', 1);
$query->where('value', 'new);
})
->whereHas('metas', function($query) {
$query->where('Meta_id', 3);
$query->where('value', 'LCD);
})
}
and then query was performed:
$query->get();
The mistake was related to ::whereHas method, what I had to do was assign whereHas result to the variable:
if($meta){
$query = $query->whereHas('metas', function($query) {
$query->where('Meta_id', 1);
$query->where('value', 'new);
})
->whereHas('metas', function($query) {
$query->where('Meta_id', 3);
$query->where('value', 'LCD);
})
}
So thats all. Always check with internals if something works unexpectadely