// 获取所有加载的Objective-C框架和动态库的名称
const char ** objc_copyImageNames ( unsigned int *outCount );

// 获取指定类所在动态库
const char * class_getImageName ( Class cls );

// 获取指定库或框架中所有类的类名
const char ** objc_copyClassNamesForImage ( const char *image, unsigned int *outCount );

NSLog(@"获取指定类所在动态库");

NSLog(@"UIView‘s Framework: %s", class_getImageName(NSClassFromString(@"UIView")));

NSLog(@"获取指定库或框架中所有类的类名");
const char ** classes = objc_copyClassNamesForImage(class_getImageName(NSClassFromString(@"UIView")), &outCount);
for (int i = 0; i < outCount; i++) {
     NSLog(@"class name: %s", classes[i]);
}

//结果
2014-11-08 12:57:32.689 [747:184013] 获取指定类所在动态库
2014-11-08 12:57:32.690 [747:184013] UIView‘s Framework: /System/Library/Frameworks/UIKit.framework/UIKit
2014-11-08 12:57:32.690 [747:184013] 获取指定库或框架中所有类的类名
2014-11-08 12:57:32.691 [747:184013] class name: UIKeyboardPredictiveSettings
2014-11-08 12:57:32.691 [747:184013] class name: _UIPickerViewTopFrame
2014-11-08 12:57:32.691 [747:184013] class name: _UIOnePartImageView
2014-11-08 12:57:32.692 [747:184013] class name: _UIPickerViewSelectionBar
2014-11-08 12:57:32.692 [747:184013] class name: _UIPickerWheelView
2014-11-08 12:57:32.692 [747:184013] class name: _UIPickerViewTestParameters
......

//先定义一个类别，添加要Swizzled的方法
@implementation UIViewController (Logging)- (void)swizzled_viewDidAppear:(BOOL)animated
{ // call original implementation
     [self swizzled_viewDidAppear:animated]; // Logging
     [Logging logWithEventName:NSStringFromClass([self class])];
}
//接下来实现swizzle方法
@implementation UIViewController (Logging)void swizzleMethod(Class class, SEL originalSelector, SEL swizzledSelector) { // the method might not exist in the class, but in its superclass
     Method originalMethod = class_getInstanceMethod(class, originalSelector);
     Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector); // class_addMethod will fail if original method already exists
     BOOL didAddMethod = class_addMethod(class, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod)); // the method doesn’t exist and we just added one
     if (didAddMethod) {
          class_replaceMethod(class, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
     }
     else {
          method_exchangeImplementations(originalMethod, swizzledMethod);
     }
}

//最后要确保在程序启动的时候调用swizzleMethod方法在之前的UIViewController的Logging类别里添加+load:方法，然后在+load:里把viewDidAppear替换掉
@implementation UIViewController (Logging)+ (void)load
{
     swizzleMethod([self class], @selector(viewDidAppear:), @selector(swizzled_viewDidAppear:));
}

//更简化直接用新的IMP取代原IMP，不是替换，只需要有全局的函数指针指向原IMP即可。
void (gOriginalViewDidAppear)(id, SEL, BOOL);void newViewDidAppear(UIViewController *self, SEL _cmd, BOOL animated)
{ // call original implementation
     gOriginalViewDidAppear(self, _cmd, animated); // Logging
     [Logging logWithEventName:NSStringFromClass([self class])];
}
+ (void)load
{
     Method originalMethod = class_getInstanceMethod(self, @selector(viewDidAppear:));
     gOriginalViewDidAppear = (void *)method_getImplementation(originalMethod); if(!class_addMethod(self, @selector(viewDidAppear:), (IMP) newViewDidAppear, method_getTypeEncoding(originalMethod))) {
          method_setImplementation(originalMethod, (IMP) newViewDidAppear);
     }
}