使用Method Swizzling为UIViewController加入自动统计功能

在使用友盟，LeanCloud，Flurry这些第三方统计服务的时候，我们经常要在UIViewController里写这样的代码：

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [MobClick beginLogPageView:@"公司信息"];
}
- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [MobClick endLogPageView:@"公司信息"];
}

Method Swizzling 是一个 基于 Objective-C的 一个小技巧，可以在运行时修改类的实现。

基于Method Swizzling，我们就可以修改UIViewController中viewWillAppear:和viewWillDisappear:的实现，自动加入统计代码。

下面是之前的一段很早以前的学习的时候写的代码，抛砖引玉。这是把当前的ViewController的名字作为页面名称统计的，实际上可以先获取下有没有一个返回页面名称的方法，或者NSString的property，没有的话再使用默认的 ViewController类名。这样方便配置页面名称，又可以精简代码。

#import "UIViewController+AutoLog.h"

@implementation UIViewController (AutoLog)


-(void)printSender: (id)sender{
    NSLog(@"sender :  => %@", NSStringFromClass([sender class]));

}

-(void)autolog_viewWillAppear: (BOOL) animated{
    NSLog(@"apper");
    NSLog(@"%@", NSStringFromClass([self class]));
    [AVAnalytics beginLogPageView:NSStringFromClass([self class])];

    [self autolog_viewWillAppear:animated];
}
-(void)autolog_viewWillDisAppear: (BOOL) animated{
    NSLog(@"disapper");
    [self autolog_viewWillAppear:animated];
    [AVAnalytics endLogPageView:NSStringFromClass([self class])];

}

@end

#import "AppDelegate.h"
#import 
#import 
#import "UIViewController+AutoLog.h"

@implementation AppDelegate

void Swizzle(Class c, SEL orig, SEL new) {
    Method origMethod = class_getInstanceMethod(c, orig);
    Method newMethod = class_getInstanceMethod(c, new);
    if(class_addMethod(c, orig, method_getImplementation(newMethod), method_getTypeEncoding(newMethod)))
        class_replaceMethod(c, new, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
    else
        method_exchangeImplementations(origMethod, newMethod);
}

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
   
    Swizzle([UIViewController class], @selector(viewWillAppear:), @selector(autolog_viewWillAppear:));
    Swizzle([UIViewController class], @selector(viewWillDisappear:), @selector(autolog_viewWillDisAppear:));

    
    [AVOSCloud setApplicationId:@"your id"
                      clientKey:@"your key"];
    [AVAnalytics trackAppOpenedWithLaunchOptions:launchOptions];
    
 
    
 
    
    return YES;
}

实际使用Method Swizzling建议使用 https://github.com/rentzsch/jrswizzle