使用 Delphi 10 编译选择目录第三次重载

Question

为什么不能编译？看起来很简单，但我不明白......是字符串数组的问题吗？错误是：

[dcc32 Error] Unit1.pas(94): E2250 There is no overloaded version of 'SelectDirectory' that can be called with these arguments.

代码如下：

{
function SelectDirectory(const StartDirectory: string; out Directories: TArray<string>; Options: TSelectDirFileDlgOpts = [];
  const Title: string = ''; const FolderNameLabel: string = ''; const OkButtonLabel: string = ''): Boolean; overload;
}

procedure TForm2.Browse1Click(Sender: TObject);
var
  iStartFolder: string;
  iDirectories: Array of string;
  iSelectedFolder: string;
begin
  iStartFolder := DesktopFolder;
  if SelectDirectory(iStartFolder, iDirectories,
    [sdHidePinnedPlaces, sdNoDereferenceLinks, sdForceShowHidden,
    sdAllowMultiselect], 'Select Folder', 'Folder', 'Ok') then
    ShowMessage(iDirectories[0]);
end;

Answer 1

第三个 SelectDirectory() 重载的第二个参数是一个 out 参数，因此您必须提供与该参数类型相同的变量。您正在尝试传递一个 array of string 变量，而应该是 System.TArray<String> 变量，因此出现错误。改用这个：

procedure TForm2.Browse1Click(Sender: TObject);
var
  iStartFolder: string;
  iDirectories: TArray<string>;
  iSelectedFolder: string;
begin
  iStartFolder := DesktopFolder;
  if SelectDirectory(iStartFolder, iDirectories,
    [sdHidePinnedPlaces, sdNoDereferenceLinks, sdForceShowHidden,
    sdAllowMultiselect], 'Select Folder', 'Folder', 'Ok') then
    ShowMessage(iDirectories[0]);
end;

虽然 TArray<String> 只是 array of string 的别名，但当与 out 参数一起使用时，它们实际上是不同的类型。

使用 Delphi 10 编译选择目录第三次重载

Compling SelectDirectory Third Overload with Delphi 10

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