检查变量值＆QUOT;没有＆QUOT; [英] Checking for the Variant value "Nothing"

问题描述

这是我碰到了，去年和SO似乎是一个好地方，记录它：）

This is something I ran into last year, and SO seems like a good place to document it :)

问：当德尔福自动化Excel（/字/ ...），我怎么能检查，如果一个Excel函数返回的变量没有（因为它被称为在VBA ）？

Q: When automating Excel (/Word/...) from Delp how can I check if an Excel function returned the variant Nothing (as it's called in VBA)?

推荐答案

VarIsClear 功能包括你的情况的类型是 varDispatch 和值零。它还包括空和未知的价值观，以及自定义变量类型。我看到它在我的Delphi 2005的源;我不知道它是如何更早地包括在内。

The VarIsClear function includes your situation where the type is varDispatch and the value is nil. It also includes empty and "unknown" values, and custom variant types. I see it in my Delphi 2005 source; I don't know how much earlier it was included.

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