计算字符串长度（处理emoji表情）

-(int)getFinalStringLength:(NSString*)inputString characterCount:(int)allCount
{
    if (nil == inputString || [inputStringisEqualToString:@""])
    {
        return  0;
    }
    
    __blockint count = 0;
    __blockint weakAllCount = allCount;
    __blockint allLength = 0;
    
    [inputString enumerateSubstringsInRange:NSMakeRange(0, inputString.length)
                               options:NSStringEnumerationByComposedCharacterSequences
                            usingBlock:^(NSString *substring,NSRange substringRange,NSRange enclosingRange,BOOL *stop){
                                count  += (1 == substring.length &&isascii([substring characterAtIndex:0]) ?1 : 2);
                                if (count <= weakAllCount)
                                {
                                    allLength += substring.length;
                                }                                
                            }];
    return allLength;
}