src/Container.php
public function isResolved(string $serviceName) : bool
    {
        if ($serviceName === 'container') {
            return true; // the container itself is always resolved
        }

        if (!isset($this->serviceResolverType[$serviceName])) {
            return false; 
        }

        if ($this->serviceResolverType[$serviceName] === static::RESOLVE_FACTORY) {
            return false;
        }

        return isset($this->resolvedSharedServices[$serviceName]);
    }
public function isResolved(string $serviceName) : bool
    {
        if ($serviceName === 'container') {
            return true; // the container itself is always resolved
        }

        if (!isset($this->serviceResolverType[$serviceName])) {
            return false; 
        }

        if ($this->serviceResolverType[$serviceName] === static::RESOLVE_FACTORY) {
            return false;
        }

        return isset($this->resolvedSharedServices[$serviceName]);
    }
Check if the given service has already been resolved / shared / initiated.
A factory service will always return false.

@param string            $serviceName The name / Identifier of the service to look for.
@return bool