iOS UIAlertView显示不出标题，及重写系统方法

最近做项目的时候，遇到一个问题，就是UIAlterView
设置了标题，但是标题一直显示不出来，但是单独出来自己写个demo,进行测试，又没问题，找了挺久的终于找到原因：

UIAlertView *alertview = [[UIAlertView alloc] initWithTitle:@"标题" message:@"这个是UIAlertView的默认样式"
delegate:nil cancelButtonTitle:@"取消" otherButtonTitles:@"好的", nil];
[alertview show];
新建工程后创建AlertView发现title可以正常显示，但是在我们的工程中就是无法显示title，感觉很奇怪；找了很久后发现，我们工程中给ViewController的系统setTitle方法重写了，由于重写ViewController的setTitle方法，导致AlertView 的setTitle无法调用，所以暂时我的解决方式是将Settitle方法先不重写，就可以简单粗暴的解决这个问题；
一下附上我们的重写系统setTitle方法，大家可以互相学习

@implementation UIViewController (Title)
+ (void)load
{
static
dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
// [self exchangeSystemMethod:@selector(setTitle:) customMethod:@selector(custom_setTitle:)];
});
}
+ (void)exchangeSystemMethod:(SEL)systemMethod customMethod:(SEL)customMethod
{
Class class = [self
class];
SEL originalSelector = systemMethod;
SEL swizzledSelector = customMethod;
Method originalMethod =
class_getInstanceMethod(class, originalSelector);
Method swizzledMethod =
class_getInstanceMethod(class, swizzledSelector);
BOOL success =
class_addMethod(class, originalSelector,
method_getImplementation(swizzledMethod),
method_getTypeEncoding(swizzledMethod));
if (success) {
class_replaceMethod(class, swizzledSelector,
method_getImplementation(originalMethod),
method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
}
- (void)custom_setTitle:(NSString *)title
{
self.navigationItem.title = title;
}