ios 根据图片大小设置button的尺寸

// 添加一个加号按钮
    UIButton *addButton = [UIButton buttonWithType:UIButtonTypeCustom];
    [addButton setImage:[UIImage imageNamed:@"tag_add_icon"] forState:UIControlStateNormal];
    addButton.x = TbTopicCellMargin;
    addButton.size = addButton.currentImage.size;
    [addButton addTarget:self action:@selector(add) forControlEvents:UIControlEventTouchUpInside];
    [self.topView addSubview:addButton];
    self.addButton = addButton;

1>咱们知道imageNamed是有缓存的，从新再次拿到同一个图片名称，内存地址打印是相同的，没必要担忧又加载了一次图片

addButton.size = [UIImage imageNamed:@"tag_add_icon"].size;

2>根据状态获取图片大小

addButton.size = [addButton imageForState:UIControlStateNormal].size;

3>根据当前图片获取图片大小

addButton.size = addButton.currentImage.size;