数组中去除重复元素

.h文件
@interface NSMutableArray (FilterElement)
/**
 *   过滤掉相同的元素
 *
 *   @return 返回一个数组
 */
- (NSMutableArray*)filterTheSameElement;
@end

.m文件
@implementation NSMutableArray (FilterElement)
/**
 *   过滤掉相同的元素
 *
 *   @return 返回一个数组
 */
- (NSMutableArray*)filterTheSameElement
{
    NSMutableSet *set = [NSMutableSet set];
    for (NSObject *obj in self) {
        [set addObject:obj];
    }
    [self removeAllObjects];
    for (NSObject *obj in set) {
        [self addObject:obj];
    }
    return self;
}

@end