如何读取引用传递的值的属性？

Question

我正在尝试编写OmniGraffle 5.3.6的脚本，其中我尝试读取layers的{​​{1}}元素，该元素已传递给函数（或处理程序，AppleScript用语）。当我运行以下内容时：

canvas

我收到以下错误：

on exportToPng(theCanvas)
    set layerCount to count of layers of theCanvas
end exportToPng

tell application "OmniGraffle Professional 5"
    set theDocument to front document
    set allCanvases to canvases of theDocument
    set theCanvas to item 1 of allCanvases
    my exportToPng(theCanvas)
end tell

但是，如果我要内联我的功能，那么一切正常：

  error "OmniGraffle Professional 5 got an error: Can’t make |layers| of
  canvas id 1 of document \"base-dependency-diagram.graffle\" into type reference."
  number -1700 from |layers| of canvas id 1 of document
  "base-dependency-diagram.graffle" to reference

我看了Passing by Reference Versus Passing by Value，但我觉得它没有帮助。它很稀疏。

Answer 1

您可以通过引用传递。但是，无论你通过哪里，它也必须有＃34;告诉应用程序＆＃34;以便应用程序可以处理传递的引用。所以你会希望你的功能像......

on exportToPng(theCanvas)
    tell application "OmniGraffle Professional 5"
      set layerCount to count of layers of theCanvas
    end tell
end exportToPng

毕竟，只有＆＃34; OmniGraffle Professional 5＆＃34;知道如何从theCanvas获取图层。