'UnsafePointer<Int8>'没有会员'toString'

Question

我正在尝试使用 SwiftGtk 帮助将 Gtk 绑定到 Swift。但是，在为 HeaderBar 添加 class 时出现错误：

/home/luis/Dropbox/Documentos/Coding/Swift/SwiftGtk/.build/checkouts/SwiftGtk--2571330441700638662/Sources/HeaderBar.swift:15:63: error: value of type 'UnsafePointer<gchar>' (aka 'UnsafePointer<Int8>') has no member 'toString'
        get { return gtk_header_bar_get_title(castedPointer())?.toString() }
                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^ ~~~~~~~~
/home/luis/Dropbox/Documentos/Coding/Swift/SwiftGtk/.build/checkouts/SwiftGtk--2571330441700638662/Sources/HeaderBar.swift:20:66: error: value of type 'UnsafePointer<gchar>' (aka 'UnsafePointer<Int8>') has no member 'toString'
        get { return gtk_header_bar_get_subtitle(castedPointer())?.toString() }
                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^ ~~~~~~~~
/home/luis/Dropbox/Documentos/Coding/Swift/SwiftGtk/.build/checkouts/SwiftGtk--2571330441700638662/Sources/HeaderBar.swift:41:75: error: value of type 'UnsafePointer<gchar>' (aka 'UnsafePointer<Int8>') has no member 'toString'
        get { return gtk_header_bar_get_decoration_layout(castedPointer())?.toString() }

似乎正在发生的事情是 Gtk.HeaderBar get_title() 方法 returns gchar，它（我认为）是 UnsafePointer 类型，它没有被正确地转换成字符串在代码中：

public var title: String? {
    get { return gtk_header_bar_get_title(castedPointer())?.toString() }
    set { gtk_header_bar_set_title(castedPointer(), newValue) }
}

public var subtitle: String? {
    get { return gtk_header_bar_get_subtitle(castedPointer())?.toString() }
    set { gtk_header_bar_set_subtitle(castedPointer(), newValue) }
}

我应该遵循哪种方法将其转换为字符串？

Answer 1

有多种方法可以从 UnsafePointer<Int8> 获取 String。请参阅 https://developer.apple.com/documentation/swift/string 上的 String 文档。这里的复杂性在于，同一串字符根据所使用的编码具有不同的字节序列表示。一种方法是使用 init(cString:encoding:)。例如，如果您知道 UnsafePointer<Int8> 变量 buf 指向的缓冲区被编码为 ASCII，您可以得到这样的字符串：

let s = String.init(cString: buf, encoding: String.Encoding.ascii)

'UnsafePointer<Int8>'没有会员'toString'

'UnsafePointer<Int8>' has no member 'toString'

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