使用runtime特性新建一个类目，然后创建一个pch 文件，里面写上 #define LogController，将其写入DEBUG宏中，发布正式版本的时候，这些日志就不会打印了，这样就能看到APP启动之后ViewController的启动顺序了

显示界面之后ViewController的启动顺序

#import "UIViewController+Debug.h"
#import <objc/objc-runtime.h>

@implementation UIViewController (Debug)

+ (void)load
{
#ifdef LogController
    Method viewWillAppear = class_getInstanceMethod(self, @selector(viewWillAppear:));
    Method logViewWillAppear = class_getInstanceMethod(self, @selector(logViewWillAppear:));
    method_exchangeImplementations(viewWillAppear, logViewWillAppear);
#endif
}

- (void)logViewWillAppear:(BOOL)animated
{
    NSString *className = NSStringFromClass([self class]);
    if ([className containsString:@"Controller"]) {
        NSLog(@"----- %@ ----- is appearing",className);
    }
    [self logViewWillAppear:animated];
}

@end