i dont understand the :self return type in php-CodePudding

i am reading Brent Roose's book Laravel, beyond crud. on page 57, he states this example:

class InvoiceQueryBuilder extends Builder
{
      public function wherePaid(): self
     {
       return $this->whereState('status', Paid::class);
     }
}

I am confused however about the :self - what is this returning?

CodePudding user response：

In this context, self is just a shortcut for whatever the current class is. So this:

class InvoiceQueryBuilder extends Builder
{
     public function wherePaid(): self
     {
         return $this->whereState('status', Paid::class);
     }
}

Is the same as this:

class InvoiceQueryBuilder extends Builder
{
     public function wherePaid(): InvoiceQueryBuilder 
     {
         return $this->whereState('status', Paid::class);
     }
}

CodePudding user response：

self is specified when you are returning an instance of the current class you're working in - in this case inside that method whereState - it is probably doing something and then returning $this.

This is useful for situations where you want to chain methods, ex:

$invoice = new InvoiceBuilder();
$invoice->wherePaid()->whereInvoiceEmailed();