VB6关键字Set是什么意思? [英] VB6 keyword Set what does it mean?

问题描述

我浏览了一个旧的 VB6 代码，我看到了这样的东西

 Set AST = CreateObject("ADODB.Stream")

我有使用 VB6 和 VB.NET 的经验，但我以前从未在我的 VB6 项目中使用过这个关键字 Set.我在网上查了很多Set的用法，我只知道Properties的用法，只有我在VB.NET中知道

公共属性 myProperty As String得到返回 _myProperty结束获取设置(值作为字符串)_myProperty = 值结束集最终财产

而且我认为 Set 在上面的代码中使用不同.这两种方法有什么区别?我想知道 Set 在 VB6 中的作用

解决方案

Set 正在为 AST 变量分配一个新的引用，而不是为(AST) 的默认属性当前引用的对象.

<小时>

网络上没有太多的 VB 6 文档，但是¹ VB.Net 的一些帮助仍然引用了旧的方法.

请参阅 为 Visual Basic 6 更改的默认属性用户:

<块引用>

在 Visual Basic 6.0 中，对象支持默认属性.例如，在 Label 控件上，Caption 是默认属性，下面示例中的两个赋值是等效的.

将 lbl 变暗作为标签lbl = "重要"lbl.Caption = "重要"

<块引用>

虽然默认属性在编写 Visual Basic 代码时启用了一定数量的速记，但它们有几个缺点:

...

• 默认属性使 Set 语句在 Visual Basic 语言中成为必需.以下示例显示了如何需要 Set 来指示要分配的对象引用而不是默认属性.

将 lbl1 作为标签，lbl2 作为标签lbl1 = "Saving" ' 为 lbl1 的 Caption 属性赋值.lbl2 = lbl1 ' 将 lbl2 的 Caption 属性替换为 lbl1 的.Set lbl2 = lbl1 ' 用对 lbl1 的对象引用替换 lbl2.

<小时>

所以，在 VB.Net 中，Let 和 Set 已经过时了(事实上，Let 在 VB 6 中已经过时了)因为语言规则变了.一个赋值A = B，如果A是一个引用，总是给A分配一个新的引用.

<小时>

¹MarkJ 在评论中提供了旧版 VB6 文档的链接.

I been browsing an old VB6 code and I saw something like this

 Set AST = CreateObject("ADODB.Stream")

I have experience using VB6 and VB.NET but I never use this keyword Set before in my VB6 projects. I researched a lot in the internet what is the use of Set and what I only know is the usage in Properties which is only I know in VB.NET

Public Property myProperty As String
    Get
      Return _myProperty
    End Get
    Set(value as String)
      _myProperty = value
    End Set
End Property

and I think Set is used differently on the code above. What is the difference of the two approaches? I want to know what does the Set do in VB6

解决方案

Set is assigning a new reference to the AST variable, rather than assigning a value to (the object currently referenced by AST)'s default property.

---

There's not much VB 6 documentation around on the web, but¹ some of the help for VB.Net still references the older ways.

See Default Property Changed for Visual Basic 6 Users:

In Visual Basic 6.0, default properties are supported on objects. On a Label control, for example, Caption is the default property, and the two assignments in the following example are equivalent.

Dim lbl As Label 
lbl = "Important" 
lbl.Caption = "Important" 

While default properties enable a certain amount of shorthand in writing Visual Basic code, they have several drawbacks:

...

• Default properties make the Set statement necessary in the Visual Basic language. The following example shows how Set is needed to indicate that an object reference, rather than a default property, is to be assigned.

Dim lbl1 As Label, lbl2 As Label 
lbl1 = "Saving" ' Assign a value to lbl1's Caption property. 
lbl2 = lbl1       ' Replace lbl2's Caption property with lbl1's. 
Set lbl2 = lbl1   ' Replace lbl2 with an object reference to lbl1. 

---

So, in VB.Net, Let and Set became obsolete (in fact, Let was already pretty much obsolete in VB 6) because the language rules changed. An assignment A = B, if A is a reference, is always assigning a new reference to A.

---

¹MarkJ has supplied links to the older VB6 documentation in the comments.

这篇关于VB6关键字Set是什么意思?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！