Vba excel пользовательский тип данных

In my last week’s Blog post I elaborated on data types and their use in VBA.

Beyond using the readily available native data types we’re all familiar with, such as Integer, Date, String and Boolean, we can define our own, user-defined data type.

What is a User-Defined Data Type?

Simply put, a user-defined data type is a group of variables of native data types.

Here’s an example of grouping together several variables to define a new data type representing (or holding) information about a vehicle:

Type Vehicle

   VIN as Long

   Make as String

   Model as String

   Year as Integer

End Type

That’s it! As simple as that.

We can now dimension variables of type Vehicle:

Dim vehLeasedCar as Vehicle

We now have a kind of a hierarchy: a variable of type Vehicle containing sub-variables of different (native) types: Long, String and Integer in this example.

We can think of the sub-variables as properties of the Vehicle-type variable and use the “dot” to address each of these sub-variables. Let’s assign some values to our vehLeasedCar variable:

vehLeasedCar.VIN = 4656418

vehLeasedCar.Make = “Ford”

vehLeasedCar.Model = “Taurus”

vehLeasedCar.Year = 2001

In the same way, we can read the values of our variable (or its sub-variables). Let’s print out our vehicle’s model:

Debug.Print vehLeasedCar.Model

Why use User-Defined Data Types?

I can think of two main reasons to make use of user-defined data types:

1. They are suitable for records arrangement in a readable format
2. They are very efficient to process, even more than collections

Think of a process that needs to store and manipulate 5,000 vehicles.

One way would be to have a two-dimensional array store a table-like structure of the vehicles. This is valid (and you know how much I love arrays), and even performant. However, it would not be that clear by viewing the code what we are doing. What do you find more telling in your code: arrCars(i,j) or arrCars(i).Model?

Let’s define another data type to store information about an employee:

Private Type TEmployeeRecord

    Name As String

    DOB As Date

    Age As Integer

    City As String

    Score As Integer

End Type

Consider how readable and self-explanatory the following Sub is, tasked with printing out all data of an employee, passed over as a TEmployeeRecord type variable:

Sub PrintEmployeeReport(employee As TEmployeeRecord)

    With employee

        Debug.Print .Name, .City, .DOB, .Age, .Score

    End With

End Sub

Storing Many Records in an Array

Of course, storing a single record, as in the above examples, is not very helpful. We typically need to store many records of data in our program.

For this, we can combine our own defined data type (record structure) with a one-dimensional array.

To illustrate this in an example, let’s pick up a list of employees with some data on them from an Excel table and arrange it in an array of employees’ records. Our table look like this:

We first use a 2-dimensional array as an interim structure to quickly read the table from the Worksheet:

Dim arrEmployees() As Variant

arrEmployees = ThisWorkbook.Worksheets("Scores").Range("ScoresTable[#Data]").Value

Next, we loop our array and transfer each employee (“row”) in the array into a new, 1-dimentional array, holding employees’ records:

Dim employees(5) As TEmployeeRecord

Dim i As Integer

For i = LBound(arrEmployees, 1) To UBound(arrEmployees, 1)

        With employees(i - 1)

            .Name = arrEmployees(i, 1)

            .DOB = arrEmployees(i, 2)

            .Age = arrEmployees(i, 3)

            .City = arrEmployees(i, 4)

            .Score = arrEmployees(i, 5)

        End With

Next i

With that, we have an efficient array of employees to work with.

We can now write a function to return the score of an employee, given a pointer to the array of employees we prepared and the employee name to look for.

Function GetScoreOfEmployee(strName As String, employees() As TEmployeeRecord) As Integer

    Dim i As Integer  

    GetScoreOfEmployee = 0 

    For i = LBound(employees) To UBound(employees)

        With employees(i)

            If (.Name = strName) Then

                GetScoreOfEmployee = .Score

                Exit For

            End If

        End With

    Next i

End Function

See how elegant and clear this function is? We’re looping the employees array, checking each employee name to match strName we’re looking for, returning his score upon a successful match.

Here’s how we can make use of the above function to ask the user for a name of an employee and get his score (we’ll store his score in the intScore variable). We’re making use of the employees array we have populated earlier with our employees:

Dim strName As String

Dim intScore As Integer

strName = InputBox("Name of employee:", "Query Employee Form")

intScore = GetScoreOfEmployee(strName, employees)

If (intScore = 0) Then

   MsgBox "Employee not found", vbOKOnly + vbInformation, "Employee Error"

Else

   MsgBox strName & "'s score: " & intScore, vbOKOnly + vbInformation, "Employee Score Result"

End If

By the way, if you are not familiar with the InputBox function, I have a detailed Blog post about it for you here. Similarly, the MsgBox function is explained here.

Unfortunately, Excel VBA doesn’t allow us to add user-defined type variables to a collection, therefore we’re missing out on a potentially very useful and efficient data structure. One can argue that if a collection is our best structure to maintain our records, we can implement our records as objects defined in a Class Module instead of a user-defined data type. Yes, I have a series of Blog posts about objects and Class Modules starting right here.

The above examples are featured in my flagship on-line course: Computer Programming with Excel VBA, in case they seemed familiar to you 😉.

Hey, a small request from me to you: please share this Blog post so that we can help more colleagues with Excel VBA.

Let’s say you are trying to create a school management system. Here, you will have different types of variables like student name, student roll no, class, etc. A school also has teachers, so there will be teacher names, teacher subject, classes, etc. Similarly, there will be many other objects like, librarian, classes, principle etc. Now having different variables for each entity in school will be messy work. How about creating a data type of student, teacher, classes, etc that stores values related to them. For this we can use defined data types of VBA.

In this article, we will learn  how you can create your own data type in VBA. They are referred to as UDTs of VBA. 

Defining a User Defined Data Type

To define a structure or UDTs in VBA we use Type___End Type block. Here’s the syntax of a UDT.

Type Tname_Of_Data_Type

   var1 as datatype   'datatype can be anything, int, array,or even UDT

   var2 as datatype

   Var3() as datatype

   ---

   VarN() as datatype

End Type

So to define a custom data type in VBA we start with Type Keyword. Then we write the name of our custom data type. It is convention to use T before the Name of Data Type so that you can differentiate between vba collections and UDTs. 

The DataTypes can be anything. And Integer, String, Variant, another UDT, Arrays, collections, anything.

To use your UDT in the program declare its variable like any other variable.

Sub UseUDT

'Declaring variable of user defined data type 

Dim myVar1 as Tname_Of_Data_Type

 Dim myVar2 as Tname_Of_Data_Type

End Sub

Simple. Now to use the variables within this UDT we use dot operator. Use the name of the data type followed by a dot and name of variable within.

Sub UseUDT

'Declaring variable of user defined data type 

 Dim myVar1 as Tname_Of_Data_Type

 Dim myVar2 as Tname_Of_Data_Type

 

 myVar1.var1="Abcd"

 myVar2.Var2="xyvz"

End Sub

Enough of the theory, let’s jump into an example to see how it works.

Create A Student Variable that Stores Information Related to Student

So we have a task to create a user defined data type that stores information related to students.

A student has a first name, last name, roll number, date of birth, class, section, subjects.

So let’s create it.

'Created a Public Student Data Type

Public Type Tstudent  

  fName As String       'For First Name

  lName As String       'For Last Name

  rNo As Integer        'For Roll Number

  clss As string        'For Class

  section As String     'For Section Name   

  subjects() As String  'For Subjects of student

End Type

'Use this Tstudent type in subroutine

Sub StudentsInfo()

 

'Creating and initializing student type variable

 Dim student1 As Tstudent

 student1.fName = "Manish"

 student1.lName = "Singh"

 student1.rNo = 12334

 student1.clss = 10

 student1.section = "A"

 ReDim student1.subjects(2)

 student1.subjects(0) = "physics"

 student1.subjects(1) = "Math"

 

 'Printing student details.

 Debug.Print (student1.fName)

 Debug.Print (student1.lName)

 Debug.Print (student1.rNo)

 Debug.Print (student1.clss)

 Debug.Print (student1.section)

 Debug.Print (student1.subjects(0))

 Debug.Print (student1.subjects(1))

End Sub

When you run the above sub it will print the result as shown below:

Creating an Array of UDTs and Accessing Elements

Similarly you can create as many as variables of Tstudent type you need. You can even create an array of  Tstudent type like any other data type.

Public Type Tstudent  

  fName As String       'For First Name

  lName As String       'For Last Name

  rNo As Integer        'For Roll Number

  clss As string        'For Class

  section As String     'For Section Name   

  subjects() As String  'For Subjects of student

End Type

'Creating an arrays of Tstudents type

Sub SchoolInfo()

Dim schoolName As String

Dim students() As Tstudent

schoolName = "Senior School"

ReDim students(10)

For i = 0 To 9

 students(i).fName = "name" & Str(i + 1)

 students(i).rNo = i + 1

Next i

Debug.Print ("Name : Roll No")

For i = 0 To 9

 Debug.Print (students(i).fName & " : " & students(i).rNo)

Next i

End Sub

When you run this code, this will be printed in the immediate window.

In the above code, first defined UDT structure before and the sub (I’ll explain later why). The we just created an array using a dim keyword like we do for any variable in VBA. 

Then we used Redim to define the size of arrays. Afterwards we use a for loop to initialize the array.

To access the structure’s  elements we use another for loop. That is it.

Why Did We Declare UDT on Top of the Module?

If we declare a UDT first in a module, outside of any subroutine or function, it is available to all the modules in the workbook. It means if you have a hundred subs and functions in a module all of them can declare Student type variables in their body. 

If the UDT is not private, it will be available to all the modules in the workbook. If want a structure (UDT) to be available only to a containing module, declare it private.

Private Type Tstudent

  fName As String

  lName As String

  rNo As Integer

  clss As Integer

  section As String

  subjects() As String

End Type

You can’t have UDT on a procedural level. It means you can’t define a user defined data type inside a subroutine or function.

Nested User Defined Types

Let’s say you have UDT called a car. Car has its own elements. Similarly you have a UDT called a bike that can have its own properties.

Now let’s say you need a data type called vehicle. Vehicle can have a car and bike as its elements. Can we do this? Yes we can do this. See the below code

Private Type Tcar

 seats As Integer

 ac As Boolean

 typ As String

 color As String

 manufacturer As String

 Dop As Date

 rc_no As String

End Type

Private Type Tbike

 seats As Integer

 typ As String

 color As String

 manufacturer As String

 Dop As Date

 rc_no As String

End Type

Private Type Tvehicle

 number_of_Vehicle As Integer

 bike As Tbike

 car As Tcar

End Type

Sub vehicleVarification()

 Dim myVehicles As Tvehicle

 

 myVehicles.number_of_Vehicle = 2

 myVehicles.bike.seats = 1

 myVehicles.bike.typ = "Racing"

 myVehicles.car.seats = "4"

 myVehicles.car.ac = True

 

 Debug.Print myVehicles.number_of_Vehicle

 Debug.Print myVehicles.bike.typ

 Debug.Print myVehicles.car.ac

End Sub

Here, we have defined three user defined data type. First is Tcar that contains some information related to cars. Second is bike, it also contains some information about bike.

The third UDT is Tvehicle. It contains one variable to store number of vehicles and two variables of Tcar and Tbike type.

Private Type Tvehicle

 number_of_Vehicle As Integer

 bike As Tbike

 car As Tcar

End Type

To access variables of Tcar and Tbike we can use Tvehicle data type. In the sub, we have defined only one variable of Tvehicle type as myVehicles. When we create this variable VBA creates variables of Tcar and Tbike too.

To initialize and access variables of Tcar and Tcar, we can use myVehicle variable. As you can see in the code.

 myVehicles.number_of_Vehicle = 2

 myVehicles.bike.seats = 1

 myVehicles.bike.typ = «Racing»

 myVehicles.car.seats = «4»

 myVehicles.car.ac = True

When we run the sub, this how result occurs.

This feature really increases the power of programming VBA exponentially. You can structure your data type like real world entities. You can create relationships between data types which can be useful in a big project.

So yeah guys, this is how you can create and use a user defined data type or structure in VBA. I hope I was able to explain it. If you have any questions regarding this article or any other VBA related questions, ask me in the comments section below. I’ll be really happy to hear from you.

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6.6. Пользовательские типы данных

06-04-Пользовательские типы данных.docm — пример к п. 6.6.

Иногда возникает необходимость в работе с данными, имеющими особенную структуру. Например, какой тип должна иметь переменная, которая может хранить код пользователя, его ФИО, возраст, адрес, телефон, дату рождения? Очевидно, что встроенными типами данных тут не обойтись. Можно, конечно, представить себе строковую переменную, которая содержит все эти данные, записанные подряд, но работать с такой переменной будет очень неудобно. В подобных случаях на помощь приходят пользовательские типы данных. Для определения нового типа данных используется конструкция Type — End Type.

Рассмотрим пример. Создадим документ Microsoft Word, добавим с помощью редактора Visual Basic новый модуль и разместим в нем такой код (листинг 6.13.):

Type Worker ' начало объявления типа данных
    Usercode As Integer
    Name As String
    Phone As String
    BirthDate As Date
End Type
Public Sub WorkWithUser()
    Dim wrk_NewUser As Worker
    Dim wrk_TestUser As Worker
    Dim str_UserName As String
    wrk_NewUser.Usercode = 1
    wrk_NewUser.Name = "Петров Петр Петрович"
    wrk_NewUser.Phone = "8(928)8888888"
    wrk_NewUser.BirthDate = #8/12/1980#
    'Обмен данными между переменными
    'пользовательского типа
    'адекватен обычному обмену
    wrk_TestUser = wrk_NewUser
    'Присвоим строковой переменной
    'значение одной из частей
    'пользовательской переменной
    str_UserName = wrk_TestUser.Name
    MsgBox ("Имя пользователя: " + str_UserName)
End Sub

Новый тип данных должен быть объявлен вне процедуры — на уровне модуля. Мы специально привели здесь, вместе с текстом объявления типа, процедуру, в которой используется этот тип. Как видите, внутри объявления типа (между Type и End Type ), находятся объявления переменных, а сразу после ключевого слова Type следует имя типа. Мы дали типу данных имя Worker, а это значит, что объявляя переменную в модуле, мы будем использовать это имя для указания ее типа данных. Имя нашего типа данных используется при объявлении переменной точно так же, как и имена встроенных типов — String, Byte и т.д. Мы объявили три переменные. wrk_NewUser типа Worker, wrk_TestUser того же типа и str_UserName — обычную строковую переменную.

После того, как переменная типа Worker объявлена, мы можем работать с ней. А именно, обращение к элементам переменной ведется через точку с использованием имен «внутренних» переменных типа. Сначала мы по очереди присваиваем каждой части переменной wrk_NewUser соответствующие значения. Далее мы присваиваем значение переменной wrk_NewUser переменной wrk_TestUser. Как видите, работа с пользовательскими переменными одинакового типа ни чем не отличается от работы с обычными переменными. Несмотря на сложную структуру переменной, обычный оператор присваивания отлично справляется с переносом значений из одной переменной в другую. Следующий этап нашей программы — извлечение значения одной из частей переменной типа Worker, а конкретно — имени пользователя, в строковую переменную str_UserName. После этого мы выводим переменную str_UserName в окне сообщения.

6.7. Константы

06-05-Константы.docm — пример к п. 6.7.

Константы очень похожи на переменные. Они имеют имена, которые строятся по тем же правилам, в них могут храниться различные значения и т.д. Главное отличие констант от переменных в том, что константы нельзя изменять в ходе выполнения программы. Это удобно в тех случаях, когда вы собираетесь много раз использовать в программе какое-то значение и хотите, чтобы оно гарантированно оставалось неизменным.

Для объявления констант используется ключевое слово Const. При объявлении константы нужно обязательно указать ее имя и присвоить ей нужное значение. При необходимости можно указать и тип константы. Вот как выглядит работа с константами в процедуре (листинг 5.24.):

Const str_Name As String = "Александр"
    Const int_Size As Double = 18000
    Dim num_NewSize As Double
    MsgBox ("Здравствуйте, " + str_Name)
    num_NewSize = int_Size * 2

Здесь мы объявили пару констант — одну строковую для хранения имени пользователя, вторую — типа Double. Строковую константу мы используем для построения строки вывода в операторе MsgBox, а числовую применяем для построения выражения, результат вычислении которого записывается в переменную num_NewSize.

В VBA имеется обширный набор встроенных констант. Они используются для работы с цветом (например, vbRed — красный и т.д.) для задания типов окон сообщений и во многих других случаях. Как правило, константы, допустимые в том или ином случае, можно найти в справочном материале, который появляется при наборе команд. Так же, подробные сведения о встроенных константах содержатся в справочной системе VBA.

6.8. Выводы

В этой лекции мы завершили обсуждение основ VBA — теперь вы можете писать простые программы. Но мы еще не разговаривали о более продвинутых возможностях программирования. О них — в следующей лекции.