本文介绍如何调用系统短信应用，发送短信
首先引入系统库MessageUI.framework,然后在控制器中引入头文件

#import <MessageUI/MessageUI.h>

接下来实现代理方法

- (void)messageComposeViewController:(MFMessageComposeViewController*)controller
                 didFinishWithResult:(MessageComposeResult)result {
    switch (result) {
        case MessageComposeResultCancelled: {
            [self.view makeToast:@"取消"];
            break;
        }
        case MessageComposeResultSent: {
            [self.view makeToast:@"发送成功"];
            break;
        }
        case MessageComposeResultFailed: {
            [self.view makeToast:@"发送失败"];
            break;
        }
    }
}

最后打开ViewController即可

MFMessageComposeViewController* viewController = [[MFMessageComposeViewController alloc] init];
        viewController.messageComposeDelegate = self;
        viewController.body = @"测试";
        [self.navigationController pushViewController:viewController animated:YES];