iOS+AOP+切片+运行时

有时候有这样的需求，对于非源码的库我们想要干涉原先的代码执行过程，常见的使用场景就是埋点，当然可以使用现成的第三方框架，aspect。

1、场景

想要在VC的viewWillAppear的执行开始和执行结束分别插入我们想要执行的代码

UIViewController+VCAOP.h

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface UIViewController (VCAOP)

@end

NS_ASSUME_NONNULL_END

UIViewController+VCAOP.m

#import "UIViewController+VCAOP.h"
#import <objc/runtime.h>
@implementation UIViewController (VCAOP)
+ (void)load
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        void(^aspect)(SEL,SEL) = ^(SEL swizsel,SEL origsel) {
            Method origMethod = class_getInstanceMethod([UIViewController class], origsel);
            Method swizMethod = class_getInstanceMethod([self class], swizsel);
            //class_getInstanceMethod 返回类的实例方法
            BOOL addMehtod = class_addMethod([UIViewController class], origsel, method_getImplementation(swizMethod), method_getTypeEncoding(swizMethod));
            //把新的方法加入到目标类中
            if (addMehtod) {
                class_replaceMethod([UIViewController class], swizsel, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
            }else {
                method_exchangeImplementations(origMethod, swizMethod);
            }
        };
        aspect(@selector(viewDidLoadA),@selector(viewDidLoad));
    });
}
- (void)viewDidLoadA
{
    [self before];
//这里不会无限循环的，因为已经被替换成viewDidLoad了
    [self viewDidLoadA];
    [self after];
}
- (void)before
{
    NSLog(@"开始执行viewWillAppear");
}
- (void)after
{
    NSLog(@"结束执行viewWillAppear");
}
@end

这样的话就实现了在viewDidLoad方法执行之前和之后添加想要的代码，但是对于类簇有个例外,所谓类簇见 下文

NSMutableArray+arrayAOP.h

#import <Foundation/Foundation.h>
NS_ASSUME_NONNULL_BEGIN
@interface NSMutableArray (arrayAOP)
@end
NS_ASSUME_NONNULL_END

NSMutableArray+arrayAOP.m

#import "NSMutableArray+arrayAOP.h"
#import <objc/runtime.h>
@implementation NSMutableArray (arrayAOP)
+ (void)load
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        void(^aspect)(SEL,SEL) = ^(SEL swizsel,SEL origsel) {
            Method origMethod = class_getInstanceMethod(objc_getClass("__NSArrayM"), origsel);
            Method swizMethod = class_getInstanceMethod([self class], swizsel);
            
            BOOL addMehtod = class_addMethod([self class], swizsel, method_getImplementation(swizMethod), method_getTypeEncoding(swizMethod));
            if (addMehtod)
            {
                class_replaceMethod([self class], swizsel, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
            }
            else
            {
                method_exchangeImplementations(origMethod, swizMethod);
            }
        };
        SEL swizsel = @selector(addObjectA:);
        SEL origsel = @selector(addObject:);
        aspect(swizsel,origsel);
    });
}

- (void)addObjectA:(id)anObject
{
    if (anObject) {
        [self addObjectA:anObject];
    }else {
        NSLog(@"数组插入nil，要崩溃了");
        [self addObjectA:@"[nil]"];
        NSLog(@"避开崩溃，数组插入nil");
    }
    
}
@end

因为NSMutableArray类型，在实际实例化之后，就是私有类了，需要通过objc_getClass("__NSArrayM")来获取类