方法:

//获取一个字符在字符串中出现的所有位置 返回一个被NSValue包装的NSRange数组
- (NSArray *)rangeOfSubString:(NSString *)subStr inString:(NSString *)string {
    if (subStr == nil && [subStr isEqualToString:@""]) {
        return nil;
    }
    NSMutableArray *rangeArray = [NSMutableArray array];
    NSString *string1 = [string stringByAppendingString:subStr];
    NSString *temp;
    for (int i = 0; i < string.length; i ++) {
        temp = [string1 substringWithRange:NSMakeRange(i, subStr.length)];
        if ([temp isEqualToString:subStr]) {
            NSRange range = {i,subStr.length};
            [rangeArray addObject:[NSValue valueWithRange:range]];
        }
    }
    return rangeArray;
}