swap-master汇率PHP库

<?php
namespace Swap\Service;
use Exchanger\Service\Service;
use Http\Client\HttpClient;
use Http\Discovery\HttpClientDiscovery;
use Http\Discovery\MessageFactoryDiscovery;
use Http\Message\RequestFactory;
class Factory
{
    private $httpClient;
    private $requestFactory;
    private $registry;
    public function __construct(HttpClient $httpClient = null, RequestFactory $requestFactory = null)
    {
        $this->httpClient = $httpClient ?: HttpClientDiscovery::find();
        $this->requestFactory = $requestFactory ?: MessageFactoryDiscovery::find();
        $this->registry = new Registry();
    }
    public function setHttpClient(HttpClient $httpClient)
    {
        $this->httpClient = $httpClient;
    }
    public function setRequestFactory(RequestFactory $requestFactory)
    {
        $this->requestFactory = $requestFactory;
    }

汇率是指一国货币与另一国货币的比率或比价，或者说是用一国货币表示的另一国货币的价格。汇率变动对一国进出口贸易有着直接的调节作用。在一定条件下，通过使本国货币对外贬值，即让汇率上升，会起到促进出口、限制进口的作用;反之,本国货币对外升值，即汇率下降,则起到限制出口、增加进口的作用。