计算字符串的长度值

/*
 计算item高度
 */
-(CGFloat)calculateItemStringLength:(NSString*)title{
    //
    NSStringDrawingOptions options =  NSStringDrawingUsesLineFragmentOrigin| NSStringDrawingUsesFontLeading;
    //
    CGRect rect = [title boundingRectWithSize:CGSizeMake(300, MAXFLOAT)options:options attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:20]} context:nil];
     //NSLog(@"%f,%f",rect.size.width,rect.size.height);
    
    return  rect.size.height;
}