runtime方法替换

╰半夏微凉° 2022-05-21 12:26 197阅读 0赞

通过方法转换，将array添加元素的方法进行转换，避免添加nil对象时出现crash情况。

#import <Foundation/Foundation.h>
    
    @interface NSMutableArray (RunTime)
    
    @end

#import "NSMutableArray+RunTime.h"
    #import <objc/runtime.h>
    
    @implementation NSMutableArray (RunTime)
    
    #pragma mark - 方法替换
    
    + (void)load
    {
        // 方法1
        static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            // 无效
    // Class class = [self class];
            // 有效
            Class class = NSClassFromString(@"__NSArrayM");
    
            SEL originalSelector = @selector(addObject:);
            SEL swizzledSelector = @selector(addObjectSafe:);
    
            Method originalMethod = class_getInstanceMethod(class, originalSelector);
            Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
    
            // judge the method named swizzledMethod is already existed.
            BOOL didAddMethod = class_addMethod(class, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
            // if swizzledMethod is already existed.
            if (didAddMethod)
            {
                class_replaceMethod(class, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
            }
            else
            {
                method_exchangeImplementations(originalMethod, swizzledMethod);
            }
        });
    
        // 方法2
        // 无效（异常：Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSArrayM insertObject:atIndex:]: object cannot be nil'）
    // Class class = [self class];
        // 有效
    // Class class = NSClassFromString(@"__NSArrayM");
    // Method oldMethod = class_getInstanceMethod(class, @selector(addObject:));
    // Method newMethod = class_getInstanceMethod(class, @selector(addObjectSafe:));
    // method_exchangeImplementations(oldMethod, newMethod);
    }
    
    - (void)addObjectSafe:(id)anObject
    {
        if (anObject)
        {
            [self addObjectSafe:anObject];
            NSLog(@"添加成功");
        }
        else
        {
            NSLog(@"添加失败，不能添加 nil 对象");
        }
    }
    
    @end