QuickTest Pro Fundas: Loops

Showing posts with label Loops. Show all posts

Using For Each...Next in QTP

A For Each...Next loop is similar to a For...Next loop. Instead of repeating the statements a specified number of times, a For Each...Next loop repeats a group of statements for each item in a collection of objects or for each element of an array. This is especially helpful if you don't know how many elements are in a collection.

In the following HTML code example, the contents of a Dictionary object is used to place text in several text boxes.

<HTML>

<HEAD><TITLE>Forms and Elements</TITLE></HEAD>

<SCRIPT LANGUAGE="VBScript">

<!--

Sub cmdChange_OnClick

   Dim d   'Create a variable

   Set d = CreateObject("Scripting.Dictionary")

   d.Add "0", "Athens"   'Add some keys and items

   d.Add "1", "Belgrade"

   d.Add "2", "Cairo"

   For Each I in d

      Document.frmForm.Elements(I).Value = D.Item(I)

   Next

End Sub

-->

</SCRIPT>

<BODY>

<CENTER>

<FORM NAME="frmForm"

<Input Type = "Text"><p>

<Input Type = "Text"><p>

<Input Type = "Text"><p>

<Input Type = "Text"><p>

<Input Type = "Button" NAME="cmdChange" VALUE="Click Here"><p>

</FORM>

</CENTER>

</BODY>

</HTML>

Using For...Next in QTP

You can use For...Next statements to run a block of statements a specific number of times. For loops, use a counter variable whose value increases or decreases with each repetition of the loop.

The following example causes a procedure called MyProc to execute 50 times. The For statement specifies the counter variable x and its start and end values. The Next statement increments the counter variable by 1.

Sub DoMyProc50Times()

   Dim x

   For x = 1 To 50

      MyProc

   Next

End Sub

Using the Step keyword, you can increase or decrease the counter variable by the value you specify. In the following example, the counter variable j is incremented by 2 each time the loop repeats. When the loop is finished, the total is the sum of 2, 4, 6, 8, and 10.

Sub TwosTotal()

   Dim j, total

   For j = 2 To 10 Step 2

      total = total + j

   Next

   MsgBox "The total is " & total

End Sub

To decrease the counter variable, use a negative Step value. You must specify an end value that is less than the start value. In the following example, the counter variable myNum is decreased by 2 each time the loop repeats. When the loop is finished, total is the sum of 16, 14, 12, 10, 8, 6, 4, and 2.

Sub NewTotal()

   Dim myNum, total

   For myNum = 16 To 2 Step -2

      total = total + myNum

   Next

   MsgBox "The total is " & total

End Sub

You can exit any For...Next statement before the counter reaches its end value by using the Exit For statement. Because you usually want to exit only in certain situations, such as when an error occurs, you should use the Exit For statement in the True statement block of an If...Then...Else statement. If the condition is False, the loop runs as usual.

Using Do Loops in QTP

You can use Do...Loop statements to run a block of statements an indefinite number of times. The statements are repeated either while a condition is True or until a condition becomes True.

Repeating Statements While a Condition is True

Use the While keyword to check a condition in a Do...Loop statement. You can check the condition before you enter the loop (as shown in the following ChkFirstWhile example), or you can check it after the loop has run at least once (as shown in the ChkLastWhile example). In the ChkFirstWhile procedure, if myNum is set to 9 instead of 20, the statements inside the loop will never run. In the ChkLastWhile procedure, the statements inside the loop run only once because the condition is already False.

Sub ChkFirstWhile()

   Dim counter, myNum

   counter = 0

   myNum = 20

   Do While myNum > 10

      myNum = myNum - 1

      counter = counter + 1

   Loop

   MsgBox "The loop made " & counter & " repetitions."

End Sub

Sub ChkLastWhile()

   Dim counter, myNum

   counter = 0

   myNum = 9

Do

      myNum = myNum - 1

      counter = counter + 1

   Loop While myNum > 10

   MsgBox "The loop made " & counter & " repetitions."

End Sub

Repeating a Statement Until a Condition Becomes True

There are two ways to use the Until keyword to check a condition in a Do...Loop statement. You can check the condition before you enter the loop (as shown in the following ChkFirstUntil example), or you can check it after the loop has run at least once (as shown in the ChkLastUntil example). As long as the condition is False, the looping occurs.

Sub ChkFirstUntil()

   Dim counter, myNum

   counter = 0

   myNum = 20

   Do Until myNum = 10

      myNum = myNum - 1

      counter = counter + 1

   Loop

   MsgBox "The loop made " & counter & " repetitions."

End Sub

Sub ChkLastUntil()

   Dim counter, myNum

   counter = 0

   myNum = 1

Do

      myNum = myNum + 1

      counter = counter + 1

   Loop Until myNum = 10

   MsgBox "The loop made " & counter & " repetitions."

End Sub

Exiting a Do...Loop Statement from Inside the Loop

You can exit a Do...Loop by using the Exit Do statement. Because you usually want to exit only in certain situations, such as to avoid an endless loop, you should use the Exit Do statement in the True statement block of an If...Then...Else statement. If the condition is False, the loop runs as usual.

In the following example, myNum is assigned a value that creates an endless loop. The If...Then...Else statement checks for this condition, preventing the endless repetition.

Sub ExitExample()

   Dim counter, myNum

      counter = 0

      myNum = 9

      Do Until myNum = 10

         myNum = myNum - 1

         counter = counter + 1

         If myNum < 10 Then Exit Do

      Loop

      MsgBox "The loop made " & counter & " repetitions."

End Sub

Making Decisions with Select Case

The Select Case structure provides an alternative to If...Then...ElseIf for selectively executing one block of statements from among multiple blocks of statements. A Select Case statement provides capability similar to the If...Then...Else statement, but it makes code more efficient and readable.

A Select Case structure works with a single test expression that is evaluated once, at the top of the structure. The result of the expression is then compared with the values for each Case in the structure. If there is a match, the block of statements associated with that Case is executed, as in the following example.

Select Case Document.Form1.CardType.Options(SelectedIndex).Text

   Case "MasterCard"

      DisplayMCLogo

      ValidateMCAccount

   Case "Visa"

      DisplayVisaLogo

      ValidateVisaAccount

   Case "American Express"

      DisplayAMEXCOLogo

      ValidateAMEXCOAccount

   Case Else

      DisplayUnknownImage

      PromptAgain

End Select

Notice that the Select Case structure evaluates an expression once at the top of the structure. In contrast, the If...Then...ElseIf structure can evaluate a different expression for each ElseIf statement. You can replace an If...Then...ElseIf structure with a Select Case structure only if each ElseIf statement evaluates the same expression.

Making Decisions Using If...Then...Else

The If...Then...Else statement is used in QTP to evaluate whether a condition is True or False and, depending on the result, to specify one or more statements to run. Usually the condition is an expression that uses a comparison operator to compare one value or variable with another. . If...Then...Else statements can be nested to as many levels as you need.

Running Statements if a Condition is True

To run only one statement when a condition is True, use the single-line syntax for the If...Then...Else statement. The following example shows the single-line syntax. Notice that this example omits the Else keyword.

Sub FixDate()

    Dim myDate

    myDate = #2/13/95#

    If myDate < Now Then myDate = Now

End Sub

To run more than one line of code, you must use the multiple-line (or block) syntax. This syntax includes the End If statement, as shown in the following example:

Sub AlertUser(value)

   If value = 0 Then

      AlertLabel.ForeColor = vbRed

      AlertLabel.Font.Bold = True

      AlertLabel.Font.Italic = True

   End If

End Sub

Running Certain Statements if a Condition is True and Running Others if a Condition is False

You can use an If...Then...Else statement to define two blocks of executable statements: one block to run if the condition is True, the other block to run if the condition is False.

Sub AlertUser(value)

   If value = 0 Then

      AlertLabel.ForeColor = vbRed

      AlertLabel.Font.Bold = True

      AlertLabel.Font.Italic = True

   Else

      AlertLabel.Forecolor = vbBlack

      AlertLabel.Font.Bold = False

      AlertLabel.Font.Italic = False

   End If

End Sub

QuickTest Pro Fundas