防止数组越界Crash示例

#import 

NS_ASSUME_NONNULL_BEGIN

@interface NSArray (PreventCrash)

@end

@interface NSMutableArray (PreventCrash)

@end

NS_ASSUME_NONNULL_END

#import "NSArray+PreventCrash.h"
#import 

@implementation NSArray (PreventCrash)

+ (void)load{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        //处理数组越界crash
        NSArray* classNameArray = @[@"__NSArrayI",@"__NSArrayM",@"__NSSingleObjectArrayI"];
        [classNameArray enumerateObjectsUsingBlock:^(NSString*  className, NSUInteger idx, BOOL * _Nonnull stop) {
            Method objectAtIndexedSubscript = class_getInstanceMethod(objc_getClass(className.UTF8String), @selector(objectAtIndexedSubscript:));
            
            NSString* swizzingSelName = [className stringByAppendingString:@"_swizzing_objectAtIndexedSubscript:"];
            SEL swizzingSEL = NSSelectorFromString(swizzingSelName);
            Method swizzingObjectAtIndexedSubscript = class_getInstanceMethod(self, swizzingSEL);
            
            
            BOOL addSuccess = class_addMethod(self, @selector(objectAtIndexedSubscript:), method_getImplementation(swizzingObjectAtIndexedSubscript), method_getTypeEncoding(swizzingObjectAtIndexedSubscript));
            if (addSuccess) {
                class_replaceMethod(self, swizzingSEL, method_getImplementation(objectAtIndexedSubscript), method_getTypeEncoding(objectAtIndexedSubscript));
            }else{
                method_exchangeImplementations(objectAtIndexedSubscript, swizzingObjectAtIndexedSubscript);
            }
        }];
        
    });
}

#pragma mark - 数组越界方法
- (id)__NSArrayI_swizzing_objectAtIndexedSubscript:(NSUInteger)idx{
    if (idx < self.count) {
        return self[idx];
    }
    return nil;
}

- (id)__NSArrayM_swizzing_objectAtIndexedSubscript:(NSUInteger)idx{
    if (idx < self.count) {
        return self[idx];
    }
    return nil;
}

- (id)__NSSingleObjectArrayI_swizzing_objectAtIndexedSubscript:(NSUInteger)idx{
    if (idx < self.count) {
        return self[idx];
    }
    return nil;
}

@end


@implementation NSMutableArray (PreventCrash)

+ (void)load{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        //处理数组add nil
        Class mutableArrayClass = objc_getClass(@"__NSArrayM".UTF8String);
        SEL mutableInsertSEL = @selector(insertObject:atIndex:);
        SEL swizzingMutableInsertSEL = @selector(__NSArrayM_insertObject:atIndex:);

        Method mutableInsertMethod = class_getInstanceMethod(mutableArrayClass, mutableInsertSEL);
        Method swizzingMutableInsertMethod = class_getInstanceMethod(self, swizzingMutableInsertSEL);

        BOOL success = class_addMethod(mutableArrayClass, mutableInsertSEL, method_getImplementation(swizzingMutableInsertMethod), method_getTypeEncoding(swizzingMutableInsertMethod));
        if (success) {
            class_addMethod(mutableArrayClass, swizzingMutableInsertSEL, method_getImplementation(mutableInsertMethod), method_getTypeEncoding(mutableInsertMethod));
        }else{
            method_exchangeImplementations(mutableInsertMethod, swizzingMutableInsertMethod);
        }
        
    });
}

#pragma mark - NSArrayM
- (void)__NSArrayM_insertObject:(id)anObject atIndex:(NSUInteger)index{
    if (!anObject) return;
    [self __NSArrayM_insertObject:anObject atIndex:index];
}

@end