//
// ViewController.m
// Runtime
//
// Created by Yuhui Huang on 12/1/16.
// Copyright © 2016 Yuhui Huang. All rights reserved.
//
#import "ViewController.h"
#import <objc/runtime.h>
///-----------------------------------------------------------------------------
/// http://nshipster.com/associated-objects
///-----------------------------------------------------------------------------
#pragma mark - Associated Objects -
/**
Associated Objects—or Associative References, as they were originally known—are a feature of the Objective-C 2.0 runtime, introduced in OS X Snow Leopard (available in iOS 4). The term refers to the following three C functions declared in <objc/runtime.h>, which allow objects to associate arbitrary values for keys at runtime:
objc_setAssociatedObject
objc_getAssociatedObject
objc_removeAssociatedObjects
Why is this useful? It allows developers to add custom properties to existing classes in categories, which is an otherwise notable shortcoming for Objective-C.
http://nshipster.com/associated-objects
*/
@interface NSObject (AssociatedObject)
@property (nonatomic, strong) id associatedObject;
@end
@implementation NSObject (AssociatedObject)
@dynamic associatedObject;
/**
It is often recommended that they key be a static char—or better yet, the
pointer to one. Basically, an arbitrary value that is guaranteed to be constant,
unique, and scoped for use within getters and setters:
static char kAssociatedObjectKey;
objc_getAssociatedObject(self, &kAssociatedObjectKey);
http://nshipster.com/associated-objects
*/
- (void)setAssociatedObject:(id)object {
objc_setAssociatedObject(self, @selector(associatedObject), object, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
- (id)associatedObject {
return objc_getAssociatedObject(self, @selector(associatedObject));
}
@end
///-----------------------------------------------------------------------------
/// http://tech.glowing.com/cn/method-swizzling-aop
///-----------------------------------------------------------------------------
#pragma mark - Method Swizzling 和 AOP 实践 -
@interface UIViewController (MethodSwizzling)
@end
@implementation UIViewController (MethodSwizzling)
/**
一般情况下，类别里的方法会重写掉主类里相同命名的方法。如果有两个类别实现了相同命名的方法，只有一个
方法会被调用。但 +load: 是个特例，当一个类被读到内存的时候， runtime 会给这个类及它的每一个类
别都发送一个 +load: 消息。
http://tech.glowing.com/cn/method-swizzling-aop
*/
+ (void)load
{
swizzleMethod([self class], @selector(viewDidAppear:), @selector(swizzled_viewDidAppear:));
}
/**
代码看起来可能有点奇怪，像递归不是么。当然不会是递归，因为在 runtime 的时候，函数实现已经被交换
了。调用 viewDidAppear: 会调用你实现的 swizzled_viewDidAppear:，而在 swizzled_viewDidAppear: 里
调用 swizzled_viewDidAppear: 实际上调用的是原来的 viewDidAppear:
http://tech.glowing.com/cn/method-swizzling-aop
*/
- (void)swizzled_viewDidAppear:(BOOL)animated
{
NSLog(@"---- swizzled_viewDidAppear 位置1 ----");
// call original implementation
[self swizzled_viewDidAppear:animated];
NSLog(@"---- swizzled_viewDidAppear 位置2 ----");
}
/**
要先尝试添加原 selector 是为了做一层保护，因为如果这个类没有实现 originalSelector ，但其父
类实现了，那 class_getInstanceMethod 会返回父类的方法。这样 method_exchangeImplementations 替
换的是父类的那个方法，这当然不是你想要的。所以我们先尝试添加 orginalSelector ，如果已经存在，再
用 method_exchangeImplementations 把原方法的实现跟新的方法实现给交换掉。
http://tech.glowing.com/cn/method-swizzling-aop
*/
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);
}
}
/**
其实，这里还可以更简化点：直接用新的 IMP 取代原 IMP ，而不是替换。只需要有全局的函数指针指向
原 IMP 就可以。
http://tech.glowing.com/cn/method-swizzling-aop
*/
//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);
// }
//}
@end
///-----------------------------------------------------------------------------
/// http://tech.glowing.com/cn/implement-kvo
///-----------------------------------------------------------------------------
#pragma mark - 如何自己动手实现 KVO -
/**
打印一个类的全部方法
http://tech.glowing.com/cn/implement-kvo
*/
static NSArray *ClassMethodNames(Class c)
{
NSMutableArray *array = [NSMutableArray array];
unsigned int methodCount = 0;
Method *methodList = class_copyMethodList(c, &methodCount);
unsigned int i;
for(i = 0; i < methodCount; i++) {
[array addObject: NSStringFromSelector(method_getName(methodList[i]))];
}
free(methodList);
return array;
}
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// self.associatedObject = @"Hello, AssociatedObject!";
// NSLog(@"%@", self.associatedObject);
// NSArray *array = ClassMethodNames([UIViewController class]);
// for (NSString *method in array) {
// NSLog(@"----%@", method);
// }
if ([self hasSelector:@selector(viewDidLoad)]) {
NSLog(@"true");
} else {
NSLog(@"false");
}
}
- (void)viewDidAppear:(BOOL)animated {
NSLog(@"---- viewDidAppear 位置1 ----");
// 父类的方法被替换了
[super viewDidAppear:animated];
NSLog(@"---- viewDidAppear 位置1 ----");
}
///-----------------------------------------------------------------------------
/// http://tech.glowing.com/cn/implement-kvo
///-----------------------------------------------------------------------------
#pragma mark - 如何自己动手实现 KVO -
/**
判断一个类是否实现了某个方法
http://tech.glowing.com/cn/implement-kvo
*/
- (BOOL)hasSelector:(SEL)selector
{
Class clazz = object_getClass(self);
unsigned int methodCount = 0;
Method* methodList = class_copyMethodList(clazz, &methodCount);
for (unsigned int i = 0; i < methodCount; i++) {
SEL thisSelector = method_getName(methodList[i]);
if (thisSelector == selector) {
free(methodList);
return YES;
}
}
free(methodList);
return NO;
}
@end
