delphi - 如果它们只是用作表单控件的指针，我是否需要 'create'/初始化局部变量？

Question

我有一个同步滚动框的简单示例，我在其中控制通过单选按钮同步哪一侧 - 同步左侧或右侧。编译时，我收到编译器消息:

[dcc32 Warning] Unit1.pas(51): W1036 Variable 'ScrlBox1' might not have been initialized

[dcc32 Warning] Unit1.pas(51): W1036 Variable 'ScrlBox2' might not have been initialized

这是一个简单的例子:

procedure TForm1.Button1Click(Sender: TObject);
var
  ScrlBox1, ScrlBox2: TScrollBox;
begin

    if radiobtn_SyncLeftSides.Checked then // Snyc Left side
    begin
      ScrlBox1 := ScrollBoxLeft1;
      ScrlBox2 := ScrollBoxLeft2;
    end
    else if radiobtn_SyncrightSides.Checked then  // Snyc Right side
    begin
      ScrlBox2 := ScrollBoxRight1;
      ScrlBox1 := ScrollBoxRight2;
    end;

    // Sync scroll boxes
    ScrlBox2.VertScrollBar.Position := ScrlBox1.VertScrollBar.Position;
    ScrlBox2.HorzScrollBar.Position := ScrlBox1.HorzScrollBar.Position;

end;

这里有什么问题？

如果我在开头添加这个消息就消失了:

ScrlBox1:= TScrollBox.Create(nil);
ScrlBox2:= TScrollBox.Create(nil);

但我不认为创建滚动框变量是必要的，对吧？这些只是指向表单控件的变量指针。

Answer 1

如果 both radiobtn_SyncLeftSides 和 radiobtn_SyncrightSides 未选中，则您没有初始化 ScrlBox1 和 ScrlBox2 变量，然后再使用它们。这就是编译器所提示的。

procedure TForm1.Button1Click(Sender: TObject);
var
  ScrlBox1, ScrlBox2: TScrollBox;
begin
  if radiobtn_SyncLeftSides.Checked then // Snyc Left side
  begin
    ScrlBox1 := ScrollBoxLeft1;
    ScrlBox2 := ScrollBoxLeft2;
  end
  else if radiobtn_SyncrightSides.Checked then  // Snyc Right side
  begin
    ScrlBox2 := ScrollBoxRight1;
    ScrlBox1 := ScrollBoxRight2;
  end else
  begin
    // NOT INITIALIZED HERE!!!!!
  end;

  // Sync scroll boxes
  ScrlBox2.VertScrollBar.Position := ScrlBox1.VertScrollBar.Position;
  ScrlBox2.HorzScrollBar.Position := ScrlBox1.HorzScrollBar.Position;
end;

如果你不想同步滚动，你应该退出程序:

procedure TForm1.Button1Click(Sender: TObject);
var
  ScrlBox1, ScrlBox2: TScrollBox;
begin
  if radiobtn_SyncLeftSides.Checked then // Snyc Left side
  begin
    ScrlBox1 := ScrollBoxLeft1;
    ScrlBox2 := ScrollBoxLeft2;
  end
  else if radiobtn_SyncrightSides.Checked then  // Snyc Right side
  begin
    ScrlBox2 := ScrollBoxRight1;
    ScrlBox1 := ScrollBoxRight2;
  end else
  begin
    Exit; // <-- HERE
  end;

  // Sync scroll boxes
  ScrlBox2.VertScrollBar.Position := ScrlBox1.VertScrollBar.Position;
  ScrlBox2.HorzScrollBar.Position := ScrlBox1.HorzScrollBar.Position;
end;