public function isSingleton(string $abstract) : bool
    {
        if (! $this->has($abstract)) {
            throw new NotFoundException("Element '$abstract' not found");
        }

        return $this->collection[$abstract] instanceof Closure === false;
    }
public function isSingleton(string $abstract) : bool
    {
        if (! $this->has($abstract)) {
            throw new NotFoundException("Element '$abstract' not found");
        }

        return $this->collection[$abstract] instanceof Closure === false;
    }
public function isSingleton ( string $ abstract ) : bool { if ( ! $ this -> has ( $ abstract ) ) { throw new NotFoundException ( "Element '$abstract' not found" ) ; } return $ this -> collection [ $ abstract ] instanceof Closure === false ; }
Verify if an element has a singleton instance.

@param  string The class name or container element name to resolve dependencies.

@throws NotFoundException When $abstract does not exists
@return bool
Verify if an element has a singleton instance .