Posted 04 January 2009 - 05:59 PM
Let me explain my interpretation of classes. When i first started learning OO design, objects baffled me as i was used to procedural VB6.0 syntax! However, the simplicity of objects began to slowly sink in (and reading many eBooks) and they are powerful for one main reason - objects encapsulate code, i.e. think of objects as a shoe box; all your code is stuffed into a shoe box and you don't need to care what the code is, all you care about is what methods and properties are available. Don't worry about things like inheritance, delegates, reflection, polymorphism, etc, they are all scare words you don't need to know about when first understanding OO, just understand that classes are black boxes of code and the battle is half won.
Using intellisense shows you this easily (much better in VB than C# imho, but i'm a noob, so i may stand corrected). For example, dropping a text box on a form, if you type textbox1. then intellisense shows you all the methods and properties (class variables) available. You don't care how the code is written, just that it is there as a simple function call like textbox1.text or textbox1.width, etc.
I also thought along these lines when i first began to learn OO; imagine you create a simple form with buttons, labels, text boxes, etc and then view the form1.vb code (double click form in design view). This is called client code and think of it as the right page of a book. Now if you create an object, this would be the left page, so the left and right pages are two distinct entities separated by the spine of the book. The only way the two pages can 'talk' to one another is by creating an instance of the class in the client code (right page) by doing Dim myObject as New Object. You can now access all methods and properties of the left hand page (class). Here, myObject is code in the right hand page analogy and Object is the class code in the left hand page. The compiler now acts like the spine of the book and links the two code spaces together, so you now have at your disposal an object called myObject that lives in memory, ready to be used.
The class is completely separate and autonomous from your forms client code and so it easily extensible for future amendments without breaking other code elsewhere. You can create many left pages (classes) and many forms (right pages) without the two ever becoming dependant on each other. You can link any left and right page by instantiating objects in the forms client code where you wish to use the object.
The whole point i've found about the importance of OO is that with procedural languages (old school VB) you can easily end up with spaghetti code (all over the place with no structure). With OO, you are separating code as it relates to distinct actions on a form for example. If designed well, it's easy to code months later as you only ever need to worry about the scope of the class code and not the whole project in general.
This snippet shows you the basics of using a Timer control on your form, creating a basic object from a class in your project and some looping to validate which numbers to display; so let's begin.
1. Create a new VB project [File/New Project] and choose [Windows Forms Application], name it what you want
2. In your solution explorer you should now have [My Project] & [Form1.vb]
3. Right click your project name in solution explorer (the one in bold) and add a class. Name it [Timer] and paste this code into the new Timer class:
'******************************************************************************************' '**** METHODOLOGY USED FOR CLASS DESIGN ****' '**** --------------------------------- ****' '**** On every tick event, need to format the value so it's [HH:MM:SS:tenths] and ****' '**** increment [m_TimerValue] by 1. Then set [m_FormattedTime] variable so it can be ****' '**** read by calling procedure in [MainForm] through its associated property. ****' '******************************************************************************************' Public Class Timer 'Private class variables (called fields). These are only accessible by methods inside the class! Private m_TimerValue As Integer Private m_FormattedTime As String Private m_Hour As Integer Private m_Minute As Integer Private m_Seconds As Integer Private m_Tenths As Integer #Region "Property declarations" 'Use a public property so the forms client code can retrieve the data held in the above class fields. 'Properties are a gateway to access class data! Public Property FormattedTime() As String Get Return m_FormattedTime End Get Set(ByVal value As String) m_FormattedTime = value End Set End Property #End Region #Region "Class constructor" '*** CLASS CONSTRUCTOR *** 'When the object is first created in the forms client code, the [New] method is always invoked first; use this to 'set up the class variables, so we are forcing correct data into the properties. Public Sub New() 'Set [m_TimerValue] to 1 so the [FormatTime] method formats correctly on first loop. 'If it's set to 0, then on first loop [m_TimerValue] isn't synced properly to the loop and 'against [HH:MM:SS:tenths]. m_TimerValue = 1 m_FormattedTime = "" m_Hour = 0 m_Minute = 0 m_Seconds = 0 m_Tenths = 0 End Sub #End Region #Region "Format timer" 'This method is called every time the [Timer] on the form 'ticks'. So if you set the timers interval to 1000, for 'example (1second) then every second this class method is called. Because we want tenths of a second 'to show, we set the timer interval to 100 = 0.1secs, i.e. the timer fires 10 times every second and when it 'does we can work out which number in the [HH:MM:SS:tenths] to change, depending on the m_TimerValue 'counter value. Public Sub TimerTick() FormatTime() m_TimerValue += 1 End Sub Public Sub ResetTimerValue() m_TimerValue = 1 End Sub Private Sub FormatTime() 'Waterfall conditional check. Basically the m_TimerValue is incremented by one every time the [TimerTick] 'is called above. If the value is less than 10 then it is just adds 1 to m_Tenths. If it equals 10 then we 'have reached the end of tenths so we need to increase the seconds value by one and reset 'm_TimerValue and m_Tenths to zero. Carry on doing this and if m_Seconds reaches 59 then we are 'ready to increment the minutes value [m_Minute] by one; same happens when minutes reaches 59 and so 'now change the hour value. Carry on doing this if you want days, weeks, years, etc by nesting the 'conditional 'trap' checks to see if values exceed the upper limit of the variable, e.g. minutes(59), 'hours(24), days(7), etc, etc. If m_TimerValue = "10" Then m_TimerValue = 0 m_Tenths = 0 If m_Seconds = 59 Then m_Seconds = 0 If m_Minute = 59 Then m_Minute = 0 If m_Hour = 59 Then m_Hour = 0 Else m_Hour += 1 End If Else m_Minute += 1 End If Else m_Seconds += 1 End If Else m_Tenths += 1 End If 'Convert to strings (as we are using a label or text box on the form. Determine if result of Hour, 'Minute or second is a single digit, if so then want each string to be two significant figures so Label.Text is 'same length. Dim sHour As String = m_Hour.ToString Dim sMinute As String = m_Minute.ToString Dim sSecond As String = m_Seconds.ToString If sSecond.Length = 1 Then sSecond = "0" + sSecond End If If sMinute.Length = 1 Then sMinute = "0" + sMinute End If If sHour.Length = 1 Then sHour = "0" + sHour End If 'Final format of Time String now available to 'client code' m_FormattedTime = sHour + ":" + sMinute + ":" + sSecond + ":" + m_Tenths.ToString End Sub 'Can reset the digital clock on the form by calling this method. Public Sub ZeroHHMMSS() m_Hour = 0 m_Minute = 0 m_Seconds = 0 m_Tenths = 0 End Sub #End Region End Class
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In your MainForm (Form1, for example) create a timer control by selecting it from the toolbox and dragging it to your form. It should appear in the bottom panel/container; set it's interval in properties box (on right) to 100. Now we can create an object of our timer class. Instantiate the following object at the class level of your form:
Public Class Form1 Private DigitalClock As New Timer() Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load End Sub End Class
Put a Timer Control on the form and a label and use this line of code in the timer tick events (double click timer control):
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick Label1.Text = DigitalClock.FormattedTime DigitalClock.TimerTick() End Sub Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Timer1.Enabled = True End Sub
Hope that helps anyone trying to format time on their forms and more importantly using a basic class & object
MultiQuote
BTW, are you asking for a second Timer Control here: quote "Put a Timer Control on the form and a label and use this line of code in the timer tick events (double click timer control):"
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