XCEngine/docs/api/containers/string/size.md

# String::Length / Capacity / Empty

```cpp
SizeType Length() const;
SizeType Capacity() const;
bool Empty() const;
```

获取字符串的长度、容量和判空状态。

**参数：** 无

**返回：**
- `Length()` - 返回字符串的字符数（不包括终止 null 字符）
- `Capacity()` - 返回已分配的存储容量
- `Empty()` - 如果字符串为空则返回 `true`

**复杂度：** 均为 O(1)

**示例：**
```cpp
#include "XCEngine/Core/Containers/String.h"
#include <iostream>

int main() {
    XCEngine::Containers::String s1;
    std::cout << "Empty: " << s1.Empty() << std::endl;  // 输出: Empty: 1

    XCEngine::Containers::String s2("Hello");
    std::cout << "Length: " << s2.Length() << std::endl;      // 输出: Length: 5
    std::cout << "Capacity: " << s2.Capacity() << std::endl;  // 输出: Capacity: 6 或更大

    s2.Reserve(100);
    std::cout << "After Reserve(100), Capacity: " << s2.Capacity() << std::endl;  // 输出: 100

    return 0;
}
```

## 相关文档

- [String 总览](string.md) - 返回类总览
- [CStr](cstr.md) - 获取 C 字符串
- [Reserve / Resize](reserve-resize.md) - 内存管理