// 因为单纯是为了防止崩溃，故没有.h文件

.m 代码如下

#pragma mark - exchange method
void exchangeClassMethod(Class anClass,SEL method1Sel, SEL method2Sel)
{
    Method method1 = class_getClassMethod(anClass, method1Sel);
    Method method2 = class_getClassMethod(anClass, method2Sel);
    method_exchangeImplementations(method1, method2);
}

void exchangeInstanceMethod(Class anClass,SEL method1Sel, SEL method2Sel)
{
    Method originalMethod = class_getInstanceMethod(anClass, method1Sel);
    Method swizzledMethod = class_getInstanceMethod(anClass, method2Sel);
    
    BOOL didAddMethod =
    class_addMethod(anClass,
                    method1Sel,
                    method_getImplementation(swizzledMethod),
                    method_getTypeEncoding(swizzledMethod));
    
    if (didAddMethod) {
        class_replaceMethod(anClass,
                            method2Sel,
                            method_getImplementation(originalMethod),
                            method_getTypeEncoding(originalMethod));
    }
    
    else {
        method_exchangeImplementations(originalMethod, swizzledMethod);
    }
    
}

@implementation NSNull (Safe)
#pragma mark - safe for string
/**
 * null string is not equal to any tring
 */
- (BOOL)isEqualToString:(NSString *)aString
{
    return NO;
}

/**
 * for this method
 * [NSString stringWithFormat:@"%@",[NSNull null]]
 * not return @"(null)" but @""
 */
- (NSString *)description
{
    return @"";
}

#pragma mark - number or string change to c number
- (NSInteger)integerValue
{
    return 0;
}
- (NSUInteger)unsignedIntegerValue
{
    return 0;
}

- (int)intValue
{
    return 0;
}
- (unsigned int)unsignedIntValue
{
    return 0;
}

- (long)longValue
{
    return  0;
}
- (unsigned long)unsignedLongValue
{
    return  0;
}
- (long long)longLongValue
{
    return  0;
}
- (unsigned long long)unsignedLongLongValue
{
    return  0;
}

- (float)floatValue
{
    return 0;
}
- (double)doubleValue
{
    return 0;
}
- (BOOL)boolValue
{
    return NO;
}

#pragma mark - safe for number
- (BOOL)isEqualToNumber:(NSNumber *)number
{
    return NO;
}
@end


@implementation NSString (Safe)
- (id)forwardingTargetForSelector:(SEL)aSelector
{
    if ([NSNumber resolveInstanceMethod:aSelector]) {
        return [NSDecimalNumber decimalNumberWithString:self];
    }
    
    return self;
}
@end

@implementation NSDictionary (Safe)

+ (void)load
{
    exchangeClassMethod(self, @selector(dictionaryWithObjects:forKeys:count:), @selector(avoidCrashDictionaryWithObjects:forKeys:count:));
}

+ (instancetype)avoidCrashDictionaryWithObjects:(const id  _Nonnull __unsafe_unretained *)objects forKeys:(const id<NSCopying>  _Nonnull __unsafe_unretained *)keys count:(NSUInteger)cnt {
    
    id instance = nil;
    
    @try {
        instance = [self avoidCrashDictionaryWithObjects:objects forKeys:keys count:cnt];
    }
    @catch (NSException *exception) {
        NSUInteger index = 0;
        id  _Nonnull __unsafe_unretained newObjects[cnt];
        id  _Nonnull __unsafe_unretained newkeys[cnt];
        
        for (int i = 0; i < cnt; i++) {
            if (objects[i] && keys[i]) {
                newObjects[index] = objects[i];
                newkeys[index] = keys[i];
                index++;
            }
        }
        instance = [self avoidCrashDictionaryWithObjects:newObjects forKeys:newkeys count:index];
    }
    @finally {
        return instance;
    }
}

@end

@implementation NSArray (Safe)

+ (void)load
{
    exchangeClassMethod([self class], @selector(arrayWithObjects:count:), @selector(AvoidCrashArrayWithObjects:count:));
    
    Class __NSArray = NSClassFromString(@"NSArray");
    Class __NSArrayI = NSClassFromString(@"__NSArrayI");
    Class __NSSingleObjectArrayI = NSClassFromString(@"__NSSingleObjectArrayI");
    Class __NSArray0 = NSClassFromString(@"__NSArray0");
    
    exchangeInstanceMethod(__NSArray, @selector(objectsAtIndexes:), @selector(avoidCrashObjectsAtIndexes:));
    exchangeInstanceMethod(__NSArrayI, @selector(objectAtIndex:), @selector(__NSArrayIAvoidCrashObjectAtIndex:));
    exchangeInstanceMethod(__NSSingleObjectArrayI, @selector(objectAtIndex:), @selector(__NSSingleObjectArrayIAvoidCrashObjectAtIndex:));
    exchangeInstanceMethod(__NSArray0, @selector(objectAtIndex:), @selector(__NSArray0AvoidCrashObjectAtIndex:));
}

+ (instancetype)AvoidCrashArrayWithObjects:(const id  _Nonnull __unsafe_unretained *)objects count:(NSUInteger)cnt {
    
    id instance = nil;
    
    @try {
        instance = [self AvoidCrashArrayWithObjects:objects count:cnt];
    }
    @catch (NSException *exception) {
        NSInteger newObjsIndex = 0;
        id  _Nonnull __unsafe_unretained newObjects[cnt];
        
        for (int i = 0; i < cnt; i++) {
            if (objects[i] != nil) {
                newObjects[newObjsIndex] = objects[i];
                newObjsIndex++;
            }
        }
        instance = [self AvoidCrashArrayWithObjects:newObjects count:newObjsIndex];
    }
    @finally {
        return instance;
    }
}

- (NSArray *)avoidCrashObjectsAtIndexes:(NSIndexSet *)indexes {
    
    NSArray *returnArray = nil;
    @try {
        returnArray = [self avoidCrashObjectsAtIndexes:indexes];
    } @catch (NSException *exception) {
        
    } @finally {
        return returnArray;
    }
}

- (id)__NSArrayIAvoidCrashObjectAtIndex:(NSUInteger)index {
    id object = nil;
    
    @try {
        object = [self __NSArrayIAvoidCrashObjectAtIndex:index];
    }
    @catch (NSException *exception) {
        
    }
    @finally {
        return object;
    }
}
- (id)__NSArray0AvoidCrashObjectAtIndex:(NSUInteger)index {
    id object = nil;
    
    @try {
        object = [self __NSArray0AvoidCrashObjectAtIndex:index];
    }
    @catch (NSException *exception) {
     
    }
    @finally {
        return object;
    }
}
- (id)__NSSingleObjectArrayIAvoidCrashObjectAtIndex:(NSUInteger)index {
    id object = nil;
    
    @try {
        object = [self __NSSingleObjectArrayIAvoidCrashObjectAtIndex:index];
    }
    @catch (NSException *exception) {
        
    }
    @finally {
        return object;
    }
}
@end