精准计算label的高度

- (CGFloat)getLableSize:(NSString *)attr{
    if (!kStringIsEmpty(attr)) {
        NSMutableParagraphStyle *ps = [[NSMutableParagraphStyle alloc] init];
        ps.alignment = NSTextAlignmentLeft;
        ps.lineHeightMultiple = 0;
        NSMutableAttributedString *str = [[NSMutableAttributedString alloc] initWithString:attr];
        [str setAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:15.0f], NSParagraphStyleAttributeName:ps} range:NSMakeRange(0, str.length)];
        CGSize size = [str boundingRectWithSize:CGSizeMake(jkScreenWidth - 121, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading context:nil].size;
        return size.height;
    }else{
        return 18;
    }
    
}