友盟统计中要求在每个页面的viewWillAppear和viewWillDisappear方法中添加友盟统计的方法：

如果是项目开始，可以考虑建个BaseViewController，或者用Category也能实现。可是如果是项目已经有了一定规模之后，再提出以上需求，就需要用到更深层次的技术（runtime）了。

新建一个viewcontroller的category

具体代码：

#import "UIViewController+UmengAnalysis.h"
#import <objc/message.h>
#import "UMMobClick/MobClick.h"@implementation UIViewController (UmengAnalysis)
+ (void)load {[super load];
// 获取两个方法的IMP（指针）Method orgMethod = class_getInstanceMethod([self class], @selector(viewWillAppear:));Method swizzledMethod = class_getInstanceMethod([self class], @selector(customViewWillAppear:));
//交换指针method_exchangeImplementations(orgMethod, swizzledMethod);Method orgDisMethod = class_getInstanceMethod([self class], @selector(viewWillDisappear:));Method swizzledDisMethod = class_getInstanceMethod([self class], @selector(customViewWillDisAppear:));method_exchangeImplementations(orgDisMethod, swizzledDisMethod);
}- (void)customViewWillAppear:(BOOL)animated {[self customViewWillAppear:animated];[MobClick beginLogPageView:NSStringFromClass([self class])];
}
- (void)customViewWillDisAppear:(BOOL)animated{[self customViewWillDisAppear:animated];[MobClick endLogPageView:NSStringFromClass([self class])];
}
@end

UILabel字体大小的问题，类似的新建一个UILabel的category

  #import "UILabel+WFFontLabel.h"  #import <objc/runtime.h>  @implementation UILabel (WFFontLabel)  + (void)load {  static dispatch_once_t onceToken;  dispatch_once(&onceToken, ^{  Class class = [self class];  // 获取两个方法的IMP（指针）  Method originalMethod2 = class_getInstanceMethod(class, @selector(setFont:));  Method swizzledMethod2 = class_getInstanceMethod(class, @selector(WFSetFont:));  // 交换IMP  method_exchangeImplementations(originalMethod2, swizzledMethod2);  });  }  - (void)WFSetFont:(UIFont *)font {  UIFont * newFont = [UIFont systemFontOfSize:font.pointSize+10];  [self WFSetFont:newFont];  }  @end

load类方法会在每个页面中被调用，在运行时，viewWillAppear

方法会被statisticsViewWillAppear替换，viewWillDisappear会被statisticsViewWillDisappear替换，且每个页面的viewWillAppear、viewWillDisappear方法仍然有效。

个人感觉这是一个很好地能解决多个页面统计的分类。