关键字“新建"在VBA中起什么作用? [英] What does the keyword 'New' do in VBA?

问题描述

在VBA程序中，通常会在实例化对现有对象实例的对象引用时不断遇到关键字 New .但是在某些实例中，我们使用关键字"New"，而在其他实例中，例如，我们不使用关键字:

In VBA procedures we are constantly meeting the keyword New usually on instantiation of an object reference to an existing object instance. But in some instantiations we use the keyword New while in others we don't for example:

Dim T As Excel.Workbook

Set T = Application.Workbooks(Bk)

在上方的示例1中，新建" 关键字未使用

In the upper example No.1 the "New" keyword has not been used

Dim fso As FileSystemObject

Set fso = New FileSystemObject

在上面的示例2中，正在使用 New 关键字

In the upper example No.2 the New keyword is being used

为什么呢?请记住，我对VBA一无所知，但我会尽我所能了解！

Why that? Keep in mind i'm fresh of the boat in VBA but i will do my best to understand!

此外，在声明对象引用时使用/不使用时，我也会感到困惑:

In addition to that i also get confused when is used/not-used in declaring an object reference for example:

Dim WS As Worksheet

在上方的示例1中，新" 关键字未使用

In the upper example No.1 the "New" keyword has not been used

Dim myClassModule As New cl_ChartEvents

在上面的示例2中，正在使用 New 关键字

In the upper example No.2 the New keyword is being used

Microsoft帮助什么都没有告诉我...

The Microsoft Help just tells me nothing...

用于隐式创建对象的关键字.如果在声明对象变量时使用新建"，则会在首次引用该对象时创建该对象的新实例，因此您不必使用Set语句来分配该对象引用.

Gratz2u

亲爱的人们，这是最后一次尘埃落定，需要深入了解

Dear people just a last dust-off for deep understanding

Dim WS as Worksheet

Set WS = Worksheets("Sheet1")

在这里，我们正在创建一个已经存在的对象，以打开MS Excel(当然，在默认模式"下为例)，这就是Sheet1. 因为它存在并且New关键字是不可能的，我们如何立即在一行中实例化该对象?

Right here we are creating an object that already existed in order to open MS Excel (lets say for examples sake in "default mode") of course which is Sheet1. Since it exists and the New keyword is out of the question how could we instantiate this object in one line right away?

4 @exantas

4 @exantas

对不起，没有足够的代表来发表照片:-(

Sorry says not enough rep to post pic :-(

推荐答案

使变量变暗时，您将指定它将保留的数据类型.在创建时，其值始终为Nothing，直到您对其进行初始化. Set T = Application.Workbook(Bk)将T变量初始化为Application.Workbook的特定实例，在本例中为"Bk".

When you Dim a variable you are specifying what data type it will hold. At the time of creation, its value is always Nothing until you initialize it. Set T = Application.Workbook(Bk) initializes the T variable to the specific instance of Application.Workbook, in this case 'Bk'.

当您使用Dim fso as FileSystemObject时，您基本上是说fso会在某个时候保留一个FileSystemObject；但是，其初始值为Nothing，直到使用Set fso = New FileSystemObject对其进行初始化为止. New关键字表示您正在创建一个新对象，而不是像使用Set T = Application.Workbook(Bk)

When you Dim fso as FileSystemObject, you are basically saying that fso will hold, at some point, a FileSystemObject; however its initial value is Nothing until you initialize it using Set fso = New FileSystemObject. The New keyword implies you're creating a new object instead of initializing the variable with an existing object as you do with Set T = Application.Workbook(Bk)

还请注意，Set fso = FileSystemObject无效，因为它不知道要分配给FileSystemObject的哪个实例.这就是为什么使用New关键字创建FileSystemObject的新实例的原因.

Also note that Set fso = FileSystemObject would be invalid because it doesn't know what instance of FileSystemObject you wish to assign to it. This is why you use the New keyword to create a new instance of FileSystemObject.

如前所述，Dim WS As Worksheet仅告诉编译器您希望变量WS容纳Worksheet对象.由于未指定其他任何内容，因此在Dim点，WS设置为Nothing

As stated before, Dim WS As Worksheet merely tells the compiler that you want variable WS to hold a Worksheet object. Since nothing else is specified, at the point of Dim, WS is set to Nothing

Dim myClassModule As New cl_ChartEvents等同于执行以下操作:

Dim myClassModule As New cl_ChartEvents is equivalent to doing:

Dim myClassModule as cl_ChartEvents
Set myClassModule = New cl_ChartEvents

...，但一行代码而不是两行代码除外.这与Dim WS As Worksheet的不同之处在于立即将变量初始化，即myClassModule设置为cl_ChartEvents的新实例，而不是Nothing.

... except on one line of code instead of two. This differs from Dim WS As Worksheet in that the variable is initialized straight away, i.e. myClassModule is set to a new instance of cl_ChartEvents instead of Nothing.

希望这会有所帮助！

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