iOS 利用runtime处理数组越界容错

.h文件

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface NSArray (LYAarrayCategory)

@end

NS_ASSUME_NONNULL_END

.m文件

#import "NSArray+LYAarrayCategory.h"
#import <objc/runtime.h>

@implementation NSArray (LYAarrayCategory)

#pragma mark - Override Base Funtion
+(void)load{
    
    [super load];
    
    //获取要替换的系统方法
    Method sysMethod1 = class_getInstanceMethod(objc_getClass("__NSArrayI"), @selector(objectAtIndex:));
    Method sysMethod2 = class_getInstanceMethod(objc_getClass("__NSArrayI"), @selector(objectAtIndexedSubscript:));
    //添加自己的方法
    Method selfMethod1 = class_getInstanceMethod(objc_getClass("__NSArrayI"), @selector(ly_objectAtIndex:));
    Method selfMethod2 = class_getInstanceMethod(objc_getClass("__NSArrayI"), @selector(ly_objectAtIndexedSubscript:));
    
    //实现方法交换
    method_exchangeImplementations(sysMethod1, selfMethod1);
    method_exchangeImplementations(sysMethod2, selfMethod2);
    
}

#pragma mark - Action && Notification
-(id)ly_objectAtIndex:(NSInteger)index{
    
    if (self.count - 1 < index) {
        
        @try {
            return [self ly_objectAtIndex:index];
        } @catch (NSException *exception) {
            
            NSLog(@"---------- %s Crash Because Method %s ----------\n",class_getName(self.class),__func__);
            NSLog(@"---------- %@",[exception callStackSymbols]);
            return nil;
            
        } @finally {
            NSLog(@"nothing to do");
        }
        
    }else{
        return [self ly_objectAtIndex:index];
    }
    
}

-(id)ly_objectAtIndexedSubscript:(NSInteger)index{
    
    if (self.count - 1 < index) {
        
        @try {
            return [self ly_objectAtIndex:index];
        } @catch (NSException *exception) {
            
            NSLog(@"---------- %s Crash Because Method %s ----------\n",class_getName(self.class),__func__);
            NSLog(@"---------- %@",[exception callStackSymbols]);
            return nil;
            
        } @finally {
            NSLog(@"nothing to do");
        }
        
    }else{
        return [self ly_objectAtIndex:index];
    }
    
}

@end