字符串中有表情的时候截取会把表情截断

/** 字符串截取 (保证表情不被截断)*/
+ (NSString *)subStringWith:(NSString *)string ToIndex:(NSInteger)index{
    
    NSString *result = string;
    if (result.length > index) {
        NSRange rangeIndex = [result rangeOfComposedCharacterSequenceAtIndex:index];
        result = [result substringToIndex:(rangeIndex.location)];
    }
    return result;
}