使用Method swizzling方法修改常用函数行为

NSObject+SafeCategory.m

//
//  NSObject+SafeCategory.m
//
//  Created by Tony on 14-4-3.
//  Copyright (c) 2014年 Tony. All rights reserved.
//

#import "NSObject+SafeCategory.h"
#import <JRSwizzle/JRSwizzle.h>


#define LOG_ERROR(err) \
do { \
    if (err) { \
        NSLog(@"Error: %@", err); \
        err = nil; \
    } \
} while(0)



@interface NSArray (SafeCategory)

- (id)TKSafe_objectAtIndex:(NSUInteger)index;

@end

@implementation NSArray (SafeCategory)

- (id)TKSafe_objectAtIndex:(NSUInteger)index
{
    if (index < self.count) {
        return [self TKSafe_objectAtIndex:index];
    } else {
#ifdef DEBUG
        NSAssert(NO, @"index %d > count %d", index, self.count);
#endif
        return nil;
    }
}

@end




@interface NSMutableArray (SafeCategory)

- (void)TKSafe_addObject:(id)anObject;

@end

@implementation NSMutableArray (SafeCategory)

- (void)TKSafe_addObject:(id)anObject
{
    if (anObject != nil) {
        [self TKSafe_addObject:anObject];
    } else {
#ifdef DEBUG
        NSAssert(NO, @"object is nil");
#endif
    }
}

@end




@implementation NSObject (SafeCategory)

+ (void)configureSafeMethods
{
    NSError *error = nil;
    
    [[[NSArray array] class] jr_swizzleMethod:@selector(objectAtIndex:)
                                   withMethod:@selector(TKSafe_objectAtIndex:)
                                        error:&error];
    LOG_ERROR(error);
    
    [[[NSMutableArray array] class] jr_swizzleMethod:@selector(objectAtIndex:)
                                          withMethod:@selector(TKSafe_objectAtIndex:)
                                               error:&error];
    LOG_ERROR(error);
    
    [[[NSMutableArray array] class] jr_swizzleMethod:@selector(addObject:)
                                          withMethod:@selector(TKSafe_addObject:)
                                               error:&error];
    LOG_ERROR(error);
}

@end