Swift字符串转wchar_t问题：LibXL写入单元格报错

我一眼就看出你的String转wchar_t的实现有核心问题——这正是LibXL仍判定你在使用试用版的原因。

为什么你的转换代码不对？ #

在macOS和iOS平台上，wchar_t是32位的UTF-32编码，但你的代码用了.utf16来生成C字符串：

• .cString(using: .utf16)返回的是16位的UTF-16字节序列
• 你直接通过memcpy把这些16位字节复制到4字节的wchar_t指针里，相当于把两个UTF-16字符打包成一个wchar_t，完全打乱了字符串的实际内容
• 结果就是你传给xlBookSetKeyW的密钥是乱码，LibXL无法识别，依然保持试用版限制，所以才会抛出“can't write row 0 in trial version”的错误

正确的String转wchar_t实现 #

下面的扩展会正确处理UTF-32到wchar_t的转换，匹配LibXL对宽字符的要求：

extension String {
    /// Converts String to a null-terminated wchar_t pointer (matches macOS/iOS UTF-32 wchar_t)
    /// Important: Remember to deallocate the pointer with `deallocate()` when finished!
    var wideChar: UnsafeMutablePointer<wchar_t>? {
        let utf32Codes = Array(self.utf32)
        let capacity = utf32Codes.count + 1 // +1 for null terminator
        
        let ptr = UnsafeMutablePointer<wchar_t>.allocate(capacity: capacity)
        defer {
            // Initialize all memory to avoid garbage values
            ptr.initialize(repeating: 0, count: capacity)
        }
        
        for (index, code) in utf32Codes.enumerated() {
            ptr[index] = wchar_t(code)
        }
        // Ensure null terminator is set (already handled by initialize, but explicit here)
        ptr[capacity - 1] = 0
        
        return ptr
    }
}

关键使用注意：内存释放 #

宽字符指针需要手动释放，否则会造成内存泄漏。建议用defer语句确保指针在代码块结束时被释放：

if let name = "John Doe".wideChar, let passKey = "mac-f.....lots of characters...3".wideChar {
    defer {
        name.deallocate()
        passKey.deallocate()
    }
    xlBookSetKeyW(book, name, passKey)
    print(">: " + String.init(cString: xlBookErrorMessageW(book)))
}

if let sheetName = "Output".wideChar, let path = savePath.wideChar, let test = "Hello".wideChar {
    defer {
        sheetName.deallocate()
        path.deallocate()
        test.deallocate()
    }
    let sheet: SheetHandle = xlBookAddSheetW(book, sheetName, nil)
    xlSheetWriteStrW(sheet, 0, 0, test, sectionTitleFormat)
    print(">: " + String.init(cString: xlBookErrorMessageW(book)))
    let success = xlBookSaveW(book, path)
    dump(success)
    print(">: " + String.init(cString: xlBookErrorMessageW(book)))
}

修复后的效果 #

修正编码转换后，LibXL能正确识别你的密钥，退出试用版模式，就不会再限制你写入第0行了，你的单元格写入操作应该能正常执行。

内容的提问来源于stack exchange，提问作者Todd