VB应用程序说没有为参数指定参数

Question

Private Function Calc(ByVal a As Decimal, ByVal Grams As Decimal) As Decimal
    ' declare variables and convert to decimal
    Grams = txtGrams.Text
    a = Grams
    Grams = a * 31.1035
    Return Grams
End Function

Private Function Calcul(ByVal b As Decimal, ByVal Ounces As Decimal) As Decimal
    Ounces = txtTroyOunces.Text
    b = Ounces
    Ounces = b * 0.911458
    Return Ounces
End Function

Private Sub btnConvert_Click(sender As System.Object, ByVal e As EventArgs) Handles btnConvert.Click
    ' determine if text boxes txtGrams and txtTroyOunces is empty
    If IsNumeric(txtGrams.Text) Then
        txtGrams.Text = Calc(txtGrams.Text)
    Else
        MessageBox.Show("Please enter a number")
    End If
End Sub

认为我是如此接近，但是没有为参数Grams指定参数。

Answer 1

你只在这里传递一个论点：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>


#define OUT_OF_MEMORY 3
#define FILE_EXTENSION ".txt"

typedef enum _Bool_ // enum _Bool_ is a non-typedef'ed enum
{
  FALSE = 0, // Enum element
  TRUE = 1 // Enum element
} Bool; // Bool is the typedef'ed enum

Bool cStringEndsWith(const char *sourceString, const char *suffix) {
  if (!sourceString || !suffix)  // Check for not null pointer
  {
    return FALSE;
  }
  size_t length_of_c_string = strlen(sourceString);
  size_t length_of_suffix = strlen(suffix);
  if (length_of_suffix > length_of_c_string) {
    return FALSE;
  }
  int compare_result = strncmp(sourceString + length_of_c_string - length_of_suffix, suffix, length_of_suffix);
  if (compare_result == 0) {
    return TRUE;
  } else {
    return FALSE;
  }
}

int prepareFileName(char **ptr_file_name){
  int ends_with_file_extension = cStringEndsWith(*ptr_file_name, FILE_EXTENSION);
  if(!ends_with_file_extension)
  {
    char *new_ptr_file_name = realloc(*ptr_file_name, strlen(*ptr_file_name) + strlen(FILE_EXTENSION) + 1);
    if(!new_ptr_file_name)
      return OUT_OF_MEMORY;
    *ptr_file_name = new_ptr_file_name;
    strcat(*ptr_file_name, FILE_EXTENSION);
  }
}

int main()
{
  char *file_name = "testFileName";
  printf("Filename unprepared: \"%s\"", file_name);
  prepareFileName(&file_name);
  printf("Filename prepared: \"%s\"", file_name);
  return 0;
}

对于期望两个的函数：

Calc(txtGrams.Text)

Answer 2

您的代码存在一些问题，所以我在这里尝试提供编译的代码，并执行我认为您打算使用代码的代码。

第一个函数从克转换为金衡盎司，所以我相应地命名了它。该函数的唯一目的是执行乘法，因此可能有点矫枉过正。但是，请注意我将D附加到常量。这是一个Decimal字面值。如果你不附加它，那么它就是Double字面值。这意味着在执行乘法之前将存在从输入Decimal值到Double值的转换。结果Double将从函数返回时转换回Decimal值。当您使用Decimal值时，通常希望避免这种精度损失。

Private Function ConvertGramsToTroyOunces(ByVal grams As Decimal) As Decimal
    Return grams*31.1035
End Function

另一个功能（未使用）变为：

Private Function ConvertOuncesToTroyOunces(ByVal ounces As Decimal) As Decimal
    Return ounces*0.911458D
End Function

按钮单击处理程序检查文本框以查看该值是否为数字，然后再次调用该函数执行转换，然后再将结果存储在文本框中：

Private Sub btnConvert_Click(sender As System.Object, ByVal e As EventArgs) Handles btnConvert.Click
    Dim grams As Decimal
    If Decimal.TryParse(txtGrams.Text, grams)
        txtGrams.Text = ConvertGramsToTroyOunces(grams)
    Else
        MessageBox.Show("Please enter a number")
    End If
End Sub

我不使用我认为是您自己实现的“遗留”Visual Basic功能的IsNumeric函数。相反，我使用Decimal.TryParse检查输入并一次执行转换。

Answer 3

试试这段代码。它会对您所拥有的内容进行几次改进：

Private Function TroyOuncesFromGrams(ByVal Grams As Decimal) As Decimal
    Return Grams * 31.1034768D
End Function

Private Function TroyOuncesFromStdOunces(ByVal Ounces As Decimal) As Decimal
    Return Ounces * 0.911458D
End Function

Private Sub btnConvert_Click(sender As System.Object, ByVal e As EventArgs) Handles btnConvert.Click
    ' determine if text boxes txtGrams and txtTroyOunces is empty
    Dim input As Decimal
    If Decimal.TryParse(txtGrams.Text, input)
        txtGrams.Text = ConvertGrams(input).ToString()
    Else
        MessageBox.Show("Please enter a number")
    End If
End Sub

并确保您已启用Option Strict或Option Infer！这样就可以解决大部分错误。

我也很想使用隐藏Module类型的Struct甚至Decimal：

Public Struct TroyOunce 

    'TODO: Implements directives for IEquatable, IConvertable, IComparable, etc to match Decimal, plus addition/subtraction operators and overloads for GetHashCode(), Equals(), CompareTo() etc

    Public Property Value As Decimal

    Public Sub New()
    End Sub

    Public Sub New(quantity As Decimal)
        Value = quantity
    End Sub

    Public Shared Widening Operator CType(ByVal ounces As TroyOunce) As Decimal
        Return ounces.Value
    End Operator

    Public Shared Narrowing Operator CType(ByVal ounces As TroyOunce) As Double
        Return CDbl(ounces.Value)
    End Operator

    Public Shared Narrowing Operator CType(ByVal ounces As TroyOunce) As Integer
        Return CInt(ounces.Value)
    End Operator

    Public Shared Widening Operator CType(ByVal ounces As Decimal) As TroyOunce
        Return New TroyOunce(ounces)
    End Operator

    Public Shared Widening Operator CType(ByVal ounces As Double) As TroyOunce
        Return New TroyOunce(CDec(ounces))
    End Operator

    Public Shared Widening Operator CType(ByVal ounces As Integer) As TroyOunce
        Return New TroyOunce(CDec(ounces))
    End Operator

    Public Shared Function FromGrams(grams As Decimal) As TroyOunce
        Return New TroyOunce(grams * 31.1034768D)
    End Function

    Public Shared Function FromStdOunces(ounces As Decimal) As TroyOunce
        Return New TroyOunce(ounces* 0.911458D)
    End Function

    Public Overrides Function ToString()
         Return Value.ToString()
    End Function

    Public Overrides Function ToString(provider As IFormatProvider)
         Return Value.ToString(provider)
    End Function

    Public Overrides Function ToString(format As String)
         Return Value.ToString(format)
    End Function

    Public Overrides Function ToString(format As String, provider As IFormatProvider)
        Return Value.ToString(format, provider)
    End Function

End Struct

完成Struct后，您可以将其视为十进制，并且您的Click事件将如下所示：

Private Sub btnConvert_Click(sender As System.Object, ByVal e As EventArgs) Handles btnConvert.Click
    ' determine if text boxes txtGrams and txtTroyOunces is empty
    Dim input As Decimal
    If Decimal.TryParse(txtGrams.Text, input)
        txtGrams.Text = TroyOunce.FromGrams(input).ToString()
    Else
        MessageBox.Show("Please enter a number")
    End If
End Sub