While...Wend
From Xojo Documentation
Repeatedly executes a series of statements while a specified condition is True.
Usage
While condition
Wend
Part | Description |
---|---|
While | Begins the loop. |
Condition | Any valid Boolean expression. When this expression evaluates to True, the loop will continue to execute. |
Statements | Statements to be executed repeatedly until condition evaluates to False. |
Continue | If a Continue statement is present, execution will skip over the remaining statements in the loop and resume with a new iteration of the loop.
Optional arguments of the Continue statement allow you to specify which loop will iterate next, in cases of multiple nested loops. |
Exit | If an Exit statement is present, execution of the loop is terminated and resumes with the next line following the loop. |
Wend | Ends the loop. Condition is evaluated to determine if the loop should exit. |
Notes
If Condition is True, all statements are executed until the Wend statement is reached. If Condition is still True, the process is repeated. If Condition is False, then execution continues with the statement following the Wend statement.
While...Wend statements can be nested to any level. Each Wend statement goes with the previous While statement. It is permissible to place Var statements inside loops, including While loops.
If a variable is declared inside a While statement, it goes out of scope after the last iteration of the loop. For example,
While I < 100
Var a As Integer
a = i + 1
Wend
MessageBox(a.ToString) // 'a' is out of scope
This loop makes sense with the variable "a" declared outside the loop.
When a loop runs, it takes over the interface, preventing the user from interacting with menus and controls. If the loop is very lengthy, you can move the code for the loop to a separate Thread, allowing it to execute in the background.
Sample Code
This example uses the While...Wend statement to increment a variable.
Using Exit:
Var attempt As Integer = 1
Var output As String
While attempt <= kAttempts
Var randomValue As Integer = Xojo.Math.RandomInt(1, 10)
If randomValue > 5 Then
output = "Found a random value above 5 after " + Str(attempt) + " iterations."
Exit
End If
attempt = attempt + 1
Wend
If attempt > kAttempts Then
output = "Found NO random value above 5 after " + Str(kAttempts) + " iterations."
End If
Using Continue:
Var matchCount As Integer
Var attempt As Integer
While attempt < kAttempts
attempt = attempt + 1
Var randomValue As Integer = Xojo.Math.RandomInt(1, 10)
If randomValue <= 5 Then
Continue
End If
matchCount = matchCount + 1
Wend
Var output As String
output = "Found " + Str(matchCount) + " random values above 5 within " + Str(kAttempts) + " iterations."
See Also
Continue, Do...Loop, Exit, For...Next statements; Application, Thread classes.