OC：Aspect简单使用

需要特殊说明的是：

• 1、hook类方法需要用元类object_getClass([Person class])调用+ (id<AspectToken>)aspect_hookSelector:(SEL)selector withOptions:(AspectOptions)options usingBlock:(id)block error:(NSError **)error;方法；
• 2、如果要全局hook某个成员方法，则需要用类名调用- (id<AspectToken>)aspect_hookSelector:(SEL)selector withOptions:(AspectOptions)options usingBlock:(id)block error:(NSError **)error;方法；
• 3、如果只是hook某个实例的某个成员方法，则需要用该类的实例去调用。

使用示例：

//Person.h
#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface Person : NSObject

+ (void)printHello;

- (void)instanceMethod;

@end

NS_ASSUME_NONNULL_END

//Person.m
#import "Person.h"

@implementation Person

+ (void)printHello {
    NSLog(@"printHello");
}

- (void)instanceMethod {
    NSLog(@"instanceMethod");
}

@end

//实现
- (void)aspects {
    
    //1. 用元类去hook类方法
    [object_getClass(Person.class) aspect_hookSelector:@selector(classMethodOfPrintHello) withOptions:AspectPositionBefore usingBlock: ^{
        NSLog(@"classMethodOfPrintHello前");
    } error:nil];
    //在调用这个方法打印之前, 会先打印上面的
    [Person classMethodOfPrintHello];

    
    //2. 用类名去全局替换
    [UIViewController aspect_hookSelector:@selector(viewDidLoad) withOptions:AspectPositionBefore usingBlock:^(id<AspectInfo> obj){
        NSLog(@"viewDidLoad前--%@", obj);
    } error:nil];
    
    
    //3. 用实例对象,只对该对象的指定成员方法起作用
    Person *per = [[Person alloc] init];
    [per aspect_hookSelector:@selector(instanceMethodOfPrintOK) withOptions:AspectPositionBefore usingBlock: ^{
        NSLog(@"instanceMethodOfPrintOK前");
    } error:nil];
    [per instanceMethodOfPrintOK];
    
    //验证3: per2在打印之前,并没有打印`instanceMethodOfPrintOK前`
    NSLog(@"======================");
    Person *per2 = [[Person alloc] init];
    [per2 instanceMethodOfPrintOK];
}

打印输出

classMethodOfPrintHello前
classMethodOfPrintHello
instanceMethodOfPrintOK前
instanceMethodOfPrintOK
======================
instanceMethodOfPrintOK
viewDidLoad前--<AspectInfo: 0x6000028c59c0>//UINavigationController
viewDidLoad前--<AspectInfo: 0x6000028fe7a0>//ViewController
viewDidLoad前--<AspectInfo: 0x6000028ffba0>//UIInputWindowController