About Visual Basic 6.0 development
Author: Suntime · NEW YORK
For programmers and programming enthusiasts, the technology in VB is a difficult point in learning. During the development of large software, the module (Moudle), Active OCX, Link Link (Active DLL) and class ( Class Moudle) constitutes a systematic, efficient software engineering, and the class's technology is the basis of control and link library technology, so the theoretical and programming methods of mastery are very meaningful.
(1) Basic definition and application overview of classes;
Class is a high-level code module that includes method, attribute, and data, which is within the scope of the module, is an Active OCX without a graphical interface. Programmers can use it as using controls, but can't see it. It is worth noting that the class cannot be inherited. Class enables us to efficiently complete complex operations for one or a few specific objects, the action of the object is the method of the class, the object's properties are the properties of the class. Relatively speaking, if the programmed object is a group of things, then we use the standard module to be very suitable, in the following two cases, you should use the class for code processing:
(1) Create a large number of objects similar to;
(2) Improve the encapsulation of the code.
The creation of the class is very simple. When you write, you can add a blank class when you select the Add Category item in the Project menu.
Class files are typically saved as extensions in .cls.
(2) Realization of methods of classes;
The method of class is similar to the interface function of the dynamic link library, which can accept the specified type parameters of other form code and pass to the class. Generally, the method of the class is to specify whether there is a return value. It is usually a public process in the class. Please see the following code example, which rejects a password box to refuse non-alphabetical inputs:
(1) Class CLS code;
Option Explicit 'variable check
Private Withevents Mytxt As TextBox
'This class accepts and controls a Text password box
DIM Isnum as boolean
'Class module variable
Public Sub Attach (Ittext As Textbox)
'Accept external variables into mytxt
Set mytxt = ittext
End Sub
Private sub mytxt_keyup (Keycode As Integer, Shift As Integer), SHIFT AS INTEGER
ISNUM = (Keycode> = 65) and (keycode <= 90)
'Test the keyboard input of the password box is English letters
IF isnum = false kil
BEEP
mytxt.text = ""
'If the input is not an English letter, the bell and clear the password box content
Msgbox "illegal character input!"
END IF
Debug.print mytxt.text
'Debug output password box content
End Sub
'Class code ends
(2) references;
The class that has been completed can be referenced by two formats. The first way: private (public or DIM) mycls (specified class name) AS New CLS (written completed class name); second way more for the program Writing a program more than "old": First, the module-level declaration in the form code - DIM MyCls AS CLS, and then performs specific definitions during the specific code - SET mycls = new CLS. In terms of the efficiency and code of the code, there may be differences, but there is no special feeling in the author's programming practice, but I use the first way because it is more convenient to write. In addition, when the code is ended, the resource occupied by using set mycls = nothing is a very good program habit. In the form form1 (the form has a password box control Text1, passworldchar = "*") Add the following code:
Option expedition
Private mycls as new CLS
'Reference CLS
Private sub flow_load ()
Mycls.attach Text1
'Starting class
End Sub
'Remember to release resources at the end of the code
Private Sub Form_Unload (Cancel AS Integer)
Set mycls = Nothing
End
End Sub
This document shows the code writing process and call mode of the class method (although it is very similar to the event of the class), its effect is that if the non-letter is entered in the password box, the system is ringing, and deletes the password box. The original data - protects the password to a certain extent. The method of the class can not require any parameters, which is similar to a PUBLIC function or process, which is also the most widely used in the class. In the next article I will discuss, how to use the class's properties, events, and methods for comprehensive programming. We discussed programming practices for classes, categories and classes of classes, in fact, the reason why the class can be widely used in software engineering, the most important point is that it can be very convenient to encapsulate many programmed properties, this Not only makes programmers overcome the complexity in the control (OCX) and link library (DLL) design and debugging, but also enhances the simplicity and efficiency of program code - this article will discuss the full class programming, including method , Attributes and basic events.
(1) Characteristics and definition of attributes of classes;
Similar to the properties of the standard control, the attributes of the class allow the user to assign values within the specified data range, which is shared by each code section within the class. The acquisition and delivery of the property needs to be programmed through the Property Let and the Property Get statement. Of course, we first need to define the corresponding variable definition of global or module-level in the class.
(2) Attributes and basic definitions of events;
Similar to the form of the form, the class also has two basic events, class_initialize (triggering time triggered) and class_terminate (triggered when unloading), both events are private. In fact, we can ignore these two events - as long as you remember to improve the methods and properties of the class.
The class can also define your own events. It is similar to the program's programming format, but only the WitHevents keyword is required to perform parameter declaration, and the event cannot have any named parameters or optional parameters, which has no return value.
In fact, the structure and attributes of the structure can be fully replaced with complex classes of the structure.
(3) Programming examples of classes, events, and attributes; the design purpose of this program is to transform all uppercase, lowercase and reverse sorting of the content of the text box in the class control form.
In order to facilitate the writing and call of the code, I reference the enumeration programming method in the class.
The following code is class Class1:
Option expedition
Private Withevents Mytxt As TextBox
'Parameter interface of the method
Public Enum Style
Lcaseit 'lowercase properties
Lbigit 'big write properties
NLOGOIT 'reverse sorting properties
END ENUM
'Custom enumeration, used to implement the automatic assignment of attributes
Private Mvarbiaozhi as Style
'Implement a web connection
Public Function Done () AS STRING '
The 'DONE method is used to be based on the specified enumeration property.
'Form text box makes the corresponding character conversion operation
'And return a transformed string
IF mvarbiaozhi = nlogoit then
Done = strreverse (MyTXT)
'Reverse sorting
Elseif mvarbiaozhi = lcaseit then
DONE = LCASE (MyTXT)
'Forced lowercase conversion
Else
DONE = ucase (mytxt)
'Force capital conversion
END IF
END FUNCTION
'DONE method ends
Public property let biaozhi (byval vdata as style)
'Get the value of the property
Mvarbiaozhi = vdata
End Property
Public property Get Biaozhi () AS Style
'Transfer attribute value to the class
Set biaozhi = mvarbiaozhi
End Property
Public Sub Attach (Ittext As Textbox)
'Method of connecting class
Set mytxt = ittext
End Sub
Private sub coplass_initialize ()
'This event is activated when loading
Msgbox "Hello! This program shows you the skills, attributes, events, and events programming!"
End Sub
Private sub coplass_terminate ()
'This event is activated when class is unloaded
Msgbox "Hello! Remember to fill in the code after being revoked in class_terminate!"
End Sub
The code of the 'class ends
(4) Quote Programming of Form Code;
Add a text control Text1, drop-down list control combo1, command button command1 (CAPTION = "start conversion"), adjust the three controls to the appropriate position.
DIM Myt as new class1
'Reference
Private sub flow_load ()
Combo1.clear
Combo1.additem "string uppercase transformation"
Combo1.addItem "string lowercase transformation"
Combo1.additem "String Reverse Sort"
Combo1.listIndex = 0
'Add attribute options in the list box
End Sub
Private submmand1_click ()
'Activate the class when the command button is pressed
myt.attach text1
'Method parameter connection
Select Case Combo1.ListIndexcase 0
Myt.biaozhi = lbigit
Case 1
myt.biaozhi = lcaseit
Case 2
myt.biaozhi = nlogoit
End SELECT
'According to the selection of the list box, assign the value of the BIAOZHI attribute of the class.
'Note, in the programming environment, the above properties value is added
TEXT1.TEXT = Myt.done
'Return the string after the end of the sort
End Sub
Private Sub Form_Unload (Cancel AS Integer)
Set myt = Nothing
End
'Good programming habits
End Sub
How, our code looks so concise, this feeling is like using a control, not only the call you want, but it is convenient to use VB's automatic prompt function.
(5) Summary of programming technology for classes;
Strictly speaking, the class is a quite useful technology in VB programming. It is also difficult to learn and master, and the application in large software engineering is very broad and effective, but in small software development, in order to improve software The efficiency and code clarity should avoid using more type modules, controls, and join libraries to replace standard modules.
The code exemplified in this article is relatively simple, but it covers all aspects of the module programming technology, I hope that beginners can learn from, and it will also hope that the programmer can discuss together. We should believe that no matter how complex high-rise buildings are all made by ordinary, the same, whether so complicated software projects are composed of basic program statements, programming enthusiasts, programmers The difference between the analyst is just that the program constructed with the same program statement is different.
