修改默认启动VC

//获取沙盒路径

NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];

NSString *filePath = [doc stringByAppendingPathComponent:@"account.plist"];

NSDictionary *account = [NSDictionary dictionaryWithContentsOfFile:filePath];

//如果沙盒中没有已经存好的accessToken

//则根视图加载为 授权页

//有，则使用默认的启动页，也就是那个mainVC

// 修改默认的启动vc

if (account == nil) {

ViewController *vc = [self.window.rootViewController.storyboard instantiateViewControllerWithIdentifier:@"oauthVC"];

self.window.rootViewController=vc;

}