iOS根据文字大小获取UILable的长度

    label.numberOfLines = 0;
    
    NSDictionary *attributes = @{NSFontAttributeName:[UIFont systemFontOfSize:12.0f],};
    
    NSString *str = @"爱仕达大大大所大所大大大大多";
    CGSize textSize = [str boundingRectWithSize:CGSizeMake(50, 100) options:NSStringDrawingTruncatesLastVisibleLine attributes:attributes context:nil].size;;
    
    [label setFrame:CGRectMake(50, 100, textSize.width, textSize.height)];
    label.textColor = [UIColor greenColor];
    label.text = str;
    [self.view addSubview:label];