VB6 变体类型 [英] VB6 Variant type

问题描述

我来自面向对象的背景.为什么在此代码片段中显示(在消息框中)测试"(注意引号).我希望逻辑测试: 'If Test = "True"' 返回 False，因为该变体包含一个布尔值而不是一个字符串.因此，我不希望出现消息框，但确实如此:

I come from an Object Oriented background. Why does "Test" (notice the quotes) display (in the message box) in this code fragment. I would expect the logical test: 'If Test = "True"' to return False because the variant contains a Boolean and not a String. Therefore I would not expect the Message Box to appear, but it does:

Dim Test As Variant

Test = True

If Test = "True" Then //line 5
    MsgBox ("Test")
End If

推荐答案

Variant VB6(以及大多数支持它们的其他语言)中的类型值会根据需要在数据类型之间自动转换；它们在 COM 交互中被广泛使用.

Variant type values in VB6 (and most other languages that support them) automatically convert between data types as needed; they're used extensively in COM interactions.

您使用的代码在此处使用了从布尔值到字符串的自动(隐式)转换:

The code you're using uses the automatic (implicit) conversion from boolean to string here:

if Test = "True"

在此处使用它作为原始分配类型(布尔值)后

after using it as it's original assigned type (boolean) here

Test = True

不过，在这里，您根本没有使用变体；您使用的是硬编码字符串 "Test".

Here, though, you're not using the variant at all; you're using a hard-coded string "Test".

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