交换某个类里面的方法

#import "objc/runtime.h"

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);
}
}

int main(int argc, char *argv[])
{
@autoreleasepool {
Swizzle([UINavigationBar class], @selector(drawRect:), @selector(SP_drawRect:));
Swizzle([UITabBar class], @selector(drawRect:), @selector(SP_drawRect:));
return UIApplicationMain(argc, argv, nil, NSStringFromClass([SNAppDelegate class]));
}
}

@interface UINavigationBar (SPExtension)

- (void)SP_drawRect:(CGRect)rect;

@end

@implementation UINavigationBar (SPExtension)

+ (Class)class {
return NSClassFromString(@"SPNavigationBar");
}

- (void)SP_drawRect:(CGRect)rect {
if (self.tag == SPCommonNavigationBar) {
if ([self viewWithTag:kSPNaviBarShadowTag] == nil) {
CGRect rf = CGRectMake(0, 0, 320, 44);
[[UIImage imageNamed:@"title_bar_background.png"] drawInRect:rf];

//            [[UIImage imageNamed:@""] drawInRect:rf];//sp_navigation_bar_bg
//            self.backgroundColor = [UIColor clearColor];

//            UIView *shadowLayer = [[UIView alloc] initWithFrame:CGRectMake(0, rect.size.height - 0, rect.size.width, 0)];
//            shadowLayer.alpha =  1.0;
//            shadowLayer.tag = kSPNaviBarShadowTag;
//
//            CAGradientLayer *grad2 = [CAGradientLayer layer];
//            grad2.frame = CGRectMake(0, 0, rect.size.width, 3);
//            grad2.colors = [NSArray arrayWithObjects:(id)[[UIColor colorWithHue:0 saturation:0 brightness:0 alpha:.0] CGColor],  (id)[[UIColor colorWithHue:0 saturation:0 brightness:0 alpha:.5] CGColor], nil];
//
//            [shadowLayer.layer insertSublayer:grad2 atIndex:0];
//            [self insertSubview:shadowLayer atIndex:10];
//            [shadowLayer release];
}
else {
UIView *shadowLayer = [self viewWithTag:kSPNaviBarShadowTag];
shadowLayer.alpha = 1.0;
shadowLayer.frame = CGRectMake(0, rect.size.height - 3, rect.size.width, 3);
CALayer *grad2 = [shadowLayer.layer.sublayers objectAtIndex:0];
grad2.frame = CGRectMake(0, 0, rect.size.width, 3);
}
} else {
UIView *shadowLayer = [self viewWithTag:kSPNaviBarShadowTag];
if (shadowLayer) {
shadowLayer.alpha = 0.0;
}
[self SP_drawRect:rect];
}
}

@end