# Rect::GetBottom

```cpp
float GetBottom() const
```

获取矩形下边界。

**返回：** `float` - 下边界坐标 (y + height)

**复杂度：** O(1)

**示例：**

```cpp
Rect rect(10.0f, 20.0f, 100.0f, 50.0f);
float bottom = rect.GetBottom();  // 70.0f
```