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vb.net - 此代码是否是此任务的正确代码？

问题描述

创建一个名为 swapped 的函数，它将接受两个名为 byref 的整数 (a,b) 并返回一个布尔值，如果数字已被交换，则返回 true。在例程中比较数字，如果 b>a 使用局部变量 temp 交换它们，则返回值 true，否则返回值 false。

Function swapped(ByRef a As Boolean, ByRef b As Boolean)
    a = True
    b = True
    If b > a Then
        temp = b
        b = a
        a = temp
        a = True
        b = True
    Else
        a = False
        b = False
    End If

标签： vb.netfunction

解决方案

首先让我们看看你的代码。

'The requirements called for 2 Integers, not Booleans.
'A Function requires a datatype, in this can a Boolean
Private Function swapped(ByRef a As Boolean, ByRef b As Boolean)
    'Assigning values here will overwrite the passed in values
    a = True
    b = True
    'What would it mean for True > True ??
    If b > a Then
        'temp isn't declared so this will not compile
        temp = b
        'here I think you are trying to do the swap
        'but all the values are True
        b = a
        a = temp
        a = True
        b = True
    Else
        a = False
        b = False

    End If
    'Function need a return value to match the datatype of the function
    'It is preceded by Return
End Function

如果您在 Visual Studio（免费下载）中工作，则会为您突出显示其中的几个错误。

现在，让我们看一些可以完成任务的代码。

'Through comments you have already figured out that a and b are Integers
'In addition, Functions always need a return type. In this case a Boolean
    Function swapped(ByRef a As Integer, ByRef b As Integer) As Boolean
    'The values of a and b are passed to the function.
    'Keep the passed in value of a in a new variable
    If b > a Then
        Dim aPassedInValue = a
        'assign the value of b to a
        a = b
        'now assign the original value of a to b
        'we can't use a because we just changed the value of a in the above line
        b = aPassedInValue
        'There have been no errors so we can return True
        Return True
    Else 'We didn't swap them
        Return False
    End If
End Function

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim c As Integer = 7
    Dim d As Integer = 20
    MessageBox.Show($"c = {c}, d = {d}", "Before Swap")
    Dim ReturnValue = swapped(c, d)
    MessageBox.Show($"The return value of the swapped Function is {ReturnValue}")
    MessageBox.Show($"c = {c}, d = {d}", "After Swap")
End Sub

我认为这个练习的重点是演示 ByRef。您已更改函数中的值，新值反映在 Button.Click Sub 的变量中。

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