More than any other assignment, file processing is in prime
need of exception handling. During file
processing, there are many things that can go wrong. For this reason, the
creation and/or management of streams should be performed in a try block
to get ready to handle exceptions that would occur. Besides actually handling
exceptions, you can use the finally
keyword to free resources.
The finally keyword is used to create a section of an
exception. Like catch, a finally block cannot exist by itself. It can be created
following a try section. The formula used would be:
try
{
}
finally
{
}
Based on this:
- The finally section has a body of its
own, delimited by its curly brackets
- Like catch, the finally section is
created after the try section
- Unlike catch, finally never
has parentheses and never takes arguments
- Unlike catch, the finally
section is always executed
Because the finally clause always gets
executed, you can include any type of code in it but it is usually appropriate
to free the resources that were allocated such as those used during streaming. Here is an example:
using namespace System;
using namespace System::IO;
int main()
{
String ^ NameOfFile = L"Members.clb";
FileStream ^ fstPersons = gcnew FileStream(NameOfFile, FileMode::Create);
BinaryWriter ^ wrtPersons = gcnew BinaryWriter(fstPersons);
try
{
wrtPersons->Write(L"James Bloch");
wrtPersons->Write(L"Catherina Wallace");
wrtPersons->Write(L"Bruce Lamont");
wrtPersons->Write(L"Douglas Truth");
}
finally
{
wrtPersons->Close();
fstPersons->Close();
}
return 0;
}
In the same way, you can use a finally section to free
resources used when reading from a stream:
using namespace System;
using namespace System::IO;
int main()
{
/* String ^ NameOfFile = L"Members.clb";
FileStream ^ fstPersons = gcnew FileStream(NameOfFile, FileMode::Create);
BinaryWriter ^ wrtPersons = gcnew BinaryWriter(fstPersons);
try
{
wrtPersons->Write(L"James Bloch");
wrtPersons->Write(L"Catherina Wallace");
wrtPersons->Write(L"Bruce Lamont");
wrtPersons->Write(L"Douglas Truth");
}
finally
{
wrtPersons->Close();
fstPersons->Close();
}*/
String ^ NameOfFile = L"Members.clb";
String ^ strLine = nullptr;
FileStream ^ fstMembers = gcnew FileStream(NameOfFile, FileMode::Open);
BinaryReader ^ rdrMembers = gcnew BinaryReader(fstMembers);
try
{
strLine = rdrMembers->ReadString();
Console::WriteLine(strLine);
strLine = rdrMembers->ReadString();
Console::WriteLine(strLine);
strLine = rdrMembers->ReadString();
Console::WriteLine(strLine);
strLine = rdrMembers->ReadString();
Console::WriteLine(strLine);
}
finally
{
rdrMembers->Close();
fstMembers->Close();
}
return 0;
}
Of course, since the whole block of code starts with a try
section, it is used for exception handling. This means that you can add the
necessary and appropriate catch section(s) but you don't have to.
Practical
Learning: Finally Releasing Resources |
|
- Start Microsoft Visual C++ and create a CLR Console
Application named IceCream4
- To create a new class, on the main menu, click Project -> Add Class...
- In the Add Class dialog box, in the Templates list, click C++ Class and
click Add
- Set the Name to CIceCream
- Make sure the Managed check box is selected and click Finish
- Change the file as follows:
#pragma once
using namespace System;
using namespace System::IO;
public ref class CIceCream sealed
{
// This is the base price of an ice scream
// Optional values may be added to it
public:
static const double BasePrice = 1.55;
// These arrays are used to build the components
// of various ice creams
private:
array<String ^> ^ Flavor;
array<String ^> ^ Container;
array<String ^> ^ Ingredient;
// Additional factor used to process an ice scream order
int Scoops;
double TotalPrice;
// Variables that will hold the user's choice
// These are declared "globally" so they can be
// shared among methods
int ChoiceFlavor;
int ChoiceContainer;
int ChoiceIngredient;
// This default constructor is the best place for
// us to initialize the array
public:
CIceCream(void);
};
|
- Access the IceCream.cpp file and change the constructor as follows:
#include "StdAfx.h"
#include "IceScream.h"
CIceCream::CIceCream(void)
{
Flavor = gcnew array<String ^>(10);
Flavor[0] = L"Vanilla";
Flavor[1] = L"Cream of Cocoa";
Flavor[2] = L"Chocolate Chip";
Flavor[3] = L"Organic Strawberry";
Flavor[4] = L"Butter Pecan";
Flavor[5] = L"Cherry Coke";
Flavor[6] = L"Chocolate Brownies";
Flavor[7] = L"Caramel Au Lait";
Flavor[8] = L"Chunky Butter";
Flavor[9] = L"Chocolate Cookie";
Ingredient = gcnew array<String^>(4);
Ingredient[0] = L"No Ingredient";
Ingredient[1] = L"Peanuts";
Ingredient[2] = L"M & M";
Ingredient[3] = L"Cookies";
Container = gcnew array<String^>(3);
Container[0] = L"Cone";
Container[1] = L"Cup";
Container[2] = L"Bowl";
}
|
- In the Class View, right-click CIceCream -> Add -> Add Function
- Set the Return Type to void
- Set the Function Name to ChooseFlavor and click Finish
- In the IceCream.cpp source file, implement the ChooseFlavor method as
follows:
// This method requests a flavor from the user and
// returns the choice
void CIceCream::ChooseFlavor(void)
{
// Make sure the user selects a valid number
//that represents a flavor...
do {
// In case the user types a symbol that
// is not a number
try {
Console::WriteLine(L"What type of flavor do you want?");
for (int i = 0; i < Flavor->Length; i++)
Console::WriteLine(L"{0} - {1}", i + 1, Flavor[i]);
Console::Write(L"Your Choice? ");
ChoiceFlavor = int::Parse(Console::ReadLine());
}
catch(FormatException ^) // display an appropriate message
{
Console::WriteLine(L"You must enter a valid number "
L"and no other character!");
}
// If the user typed an invalid number out of the
// allowed range
// let him or her know and provide another chance
if( (ChoiceFlavor < 1) || (ChoiceFlavor > Flavor->Length) )
Console::WriteLine(L"Invalid Choice - Try Again!\n");
} while (ChoiceFlavor < 1 || ChoiceFlavor > Flavor->Length);
}
|
- In the Class View, right-click CIceCream -> Add -> Add Function
- Set the Return Type to void
- Set the Function Name to ChooseContainer and click Finish
- In the IceCream.cpp source file, implement the ChooseContainer method as
follows:
void CIceCream::ChooseContainer(void)
{
// Make sure the user selects a valid number that
// represents a container
do {
// If the user types a symbol that is not a number
try {
Console::WriteLine(L"What type of container do you want?");
for (int i = 0; i < Container->Length; i++)
Console::WriteLine(L"{0} - {1}", i + 1, Container[i]);
Console::Write(L"Your Choice? ");
ChoiceContainer = int::Parse(Console::ReadLine());
}
catch(FormatException ^) // display an appropriate message
{
Console::WriteLine(L"You must enter a valid "
L"number and no other character!");
}
// If the user typed an invalid number out of the
// allowed range
// let him or her know and provide another chance
if( (ChoiceContainer < 1) ||
(ChoiceContainer > Container->Length) )
Console::WriteLine(L"Invalid Choice - Try Again!");
} while( (ChoiceContainer < 1) ||
(ChoiceContainer > Container->Length) );
}
|
- In the Class View, right-click CIceCream -> Add -> Add Function
- Set the Return Type to void
- Set the Function Name to ChooseIngredient and click Finish
- In the IceCream.cpp source file, implement the ChooseIngredient method as
follows:
void CIceCream::ChooseIngredient(void)
{
do {
try {
Console::WriteLine(L"Do you want an ingredient or not");
for (int i = 0; i < Ingredient->Length; i++)
Console::WriteLine(L"{0} - {1}",
i + 1,
Ingredient[i]);
Console::Write(L"Your Choice? ");
ChoiceIngredient = int::Parse(Console::ReadLine());
}
catch(FormatException ^)
{
Console::WriteLine(L"You must enter a valid "
L"number and no other character!");
}
if( (ChoiceIngredient < 1) ||
(ChoiceIngredient > Ingredient->Length) )
Console::WriteLine(L"Invalid Choice - Try Again!");
} while( (ChoiceIngredient < 1) ||
(ChoiceIngredient > Ingredient->Length) );
}
|
- In the Class View, right-click CIceCream -> Add -> Add Function
- Set the Return Type to void
- Set the Function Name to SpecifyNumberOfScoops and click Finish
- In the IceCream.cpp source file, implement the SpecifyNumberOfScoops
method as follows:
void CIceCream::SpecifyNumberOfScoops(void)
{
do {
try {
Console::Write(L"How many scoops(1, 2, or 3)? ");
Scoops = int::Parse(Console::ReadLine());
}
catch(FormatException ^)
{
Console::WriteLine(L"You must enter a valid number "
L"and no other character!");
}
if( (Scoops < 1) || (Scoops > 3) )
Console::WriteLine(L"Invalid Choice - Try Again!");
} while (Scoops < 1 || Scoops > 3);
}
|
- In the Class View, right-click CIceCream -> Add -> Add Function
- Set the Return Type to void
- Set the Function Name to ProcessAnOrder and click Finish
- In the IceCream.cpp source file, implement the ProcessAnOrder method as
follows:
void CIceCream::ProcessAnOrder(void)
{
double PriceIngredient, PriceScoop;
// Let the user know that this is a vending machine
Console::WriteLine(L"=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=");
Console::WriteLine(L"Ice Scream Vending Machine");
Console::WriteLine(L"-----------------------------------");
// Let the user select the components of the ice scream
ChooseFlavor();
Console::WriteLine(L"-----------------------------------");
ChooseContainer();
Console::WriteLine(L"-----------------------------------");
ChooseIngredient();
Console::WriteLine(L"-----------------------------------");
SpecifyNumberOfScoops();
Console::WriteLine(L"-----------------------------------");
// If the user selects an ingredient instead of "No Ingredient",
// add $0.50 to the order
if( (ChoiceIngredient == 2) ||
(ChoiceIngredient == 3) ||
(ChoiceIngredient == 4) )
PriceIngredient = 0.50;
else
PriceIngredient = 0.00;
// Instead of multiplying a number scoops to a value,
// We will use an incremental value depending on
// the number of scoops
if( Scoops == 1 )
PriceScoop = 0.65;
else if( Scoops == 2 )
PriceScoop = 1.05;
else
PriceScoop = 1.55;
// Calculate the total price of the ice scream
TotalPrice = BasePrice + PriceScoop + PriceIngredient;
// Create the ice scream...
// And display a receipt to the user
DisplayReceipt();
}
|
- In the Class View, right-click CIceCream -> Add -> Add Function
- Set the Return Type to void
- Set the Function Name to DisplayReceipt and click Finish
- In the IceCream.cpp source file, implement the DisplayReceipt method as
follows:
void CIceCream::DisplayReceipt(void)
{
Console::WriteLine(L"\n=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=");
Console::WriteLine(L"Ice Scream Order");
Console::WriteLine(L"-----------------------------------");
Console::WriteLine(L"Flavor: {0}",
Flavor[ChoiceFlavor - 1]);
Console::WriteLine(L"Container: {0}",
Container[ChoiceContainer - 1]);
Console::WriteLine(L"Ingredient: {0}",
Ingredient[ChoiceIngredient - 1]);
Console::WriteLine(L"Scoops: {0}", Scoops);
Console::WriteLine(L"Total Price: {0:C}", TotalPrice);
Console::WriteLine(L"=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=\n");
}
|
- In the Class View, right-click CIceCream -> Add -> Add Function
- Set the Return Type to void
- Set the Function Name to SaveOrder and click Finish
- In the IceCream.cpp source file, implement the SaveOrder method as
follows:
void CIceCream::SaveOrder(void)
{
String ^ strNameOfFile;
Console::Write(L"Please enter your initials or the name "
L"we will use to remember your order: ");
strNameOfFile = Console::ReadLine();
strNameOfFile = strNameOfFile + L".icr";
// Find out if the user entered a name of a file
// that is already in the machine
if( File::Exists(strNameOfFile) )
{
String ^ answer;
FileStream ^ stmIceScream =
gcnew FileStream(strNameOfFile, FileMode::Create);
BinaryWriter ^ bnwIceScream =
gcnew BinaryWriter(stmIceScream);
try {
// If so, find out if the user wants to
// replace the old file
Console::WriteLine(L"The file you entered exists already.");
Console::Write(L"Do you want to replace it(y/n)?");
answer = Console::ReadLine();
// If the customer wants to replace it...
if( (answer == L"y") || (answer == L"Y") )
{
// ... do so
Console::WriteLine(L"The former order with the same "
L"name will be replaced");
Console::WriteLine(
L"\n=-= Ice Scream Vending Machine =-=");
Console::WriteLine(L" Saving Order: {0}", strNameOfFile);
bnwIceScream::Write(Flavor[ChoiceFlavor - 1]);
bnwIceScream::Write(Container[ChoiceContainer - 1]);
bnwIceScream::Write(Ingredient[ChoiceIngredient - 1]);
bnwIceScream::Write(Scoops);
bnwIceScream::Write(TotalPrice);
}
// If the customer wants to save the new order with
// a different name
else if( (answer == L"n") || answer == L"N") )
{
// Ask the user to enter a name to remember the order
Console::Write(L"Please enter a name we will use "
L"to remember this order: ");
strNameOfFile = Console::ReadLine();
strNameOfFile = strNameOfFile + L".icr";
stmIceScream =
gcnew FileStream(strNameOfFile, FileMode::Create);
bnwIceScream = gcnew BinaryWriter(stmIceScream);
Console::WriteLine(
L"\n=-= Ice Scream Vending Machine =-=");
Console::WriteLine(L" Saving Order: {0}", strNameOfFile);
bnwIceScream::Write(Flavor[ChoiceFlavor - 1]);
bnwIceScream::Write(Container[ChoiceContainer - 1]);
bnwIceScream::Write(Ingredient[ChoiceIngredient - 1]);
bnwIceScream::Write(Scoops);
bnwIceScream::Write(TotalPrice);
}
else
Console::WriteLine(L"Invalid Answer - We will close");
}
finally
{
bnwIceScream->Close();
stmIceScream->Close();
}
}
else
{
FileStream ^ stmIceScream =
gcnew FileStream(strNameOfFile, FileMode::Create);
BinaryWriter ^ bnwIceScream =
gcnew BinaryWriter(stmIceScream);
try {
Console::WriteLine(L"\n=-= Ice Scream Vending Machine =-=");
Console::WriteLine(L" Saving Order: {0}", strNameOfFile);
bnwIceScream::Write(Flavor[ChoiceFlavor - 1]);
bnwIceScream::Write(Container[ChoiceContainer - 1]);
bnwIceScream::Write(Ingredient[ChoiceIngredient - 1]);
bnwIceScream::Write(Scoops);
bnwIceScream::Write(TotalPrice);
}
finally
{
bnwIceScream->Close();
stmIceScream->Close();
}
}
}
|
- In the Class View, right-click CIceCream -> Add -> Add Function
- Set the Return Type to void
- Set the Function Name to OpenOrder and click Finish
- In the IceCream.cpp source file, implement the OpenOrder method as
follows:
void CIceCream::OpenOrder(void)
{
String ^ strNameOfFile;
String ^ SelectedFlavor;
String ^ SelectedContainer;
String ^ SelectedIngredient;
// Ask the user to enter a name of a previously saved order
Console::Write(L"Please enter the name you previously "
L"gave to remember your order: ");
strNameOfFile = Console::ReadLine();
strNameOfFile = strNameOfFile + L".icr";
FileStream ^ stmIceScream =
gcnew FileStream(strNameOfFile, FileMode::Open);
BinaryReader ^ bnrIceScream =
gcnew BinaryReader(stmIceScream);
try {
// Find out if this order was previously saved in the machine
if( File::Exists(strNameOfFile) )
{
// If so, open it
SelectedFlavor = bnrIceScream->ReadString();
SelectedContainer = bnrIceScream->ReadString();
SelectedIngredient = bnrIceScream->ReadString();
Scoops = bnrIceScream->ReadInt32();
TotalPrice = bnrIceScream->ReadDouble();
// And display it to the user
Console::WriteLine(L"\n=-= Ice Scream Vending Machine =-=");
Console::WriteLine(L" Previous Order: {0}", strNameOfFile);
Console::WriteLine(L"Flavor: {0}", SelectedFlavor);
Console::WriteLine(L"Container: {0}", SelectedContainer);
Console::WriteLine(L"Ingredient: {0}", SelectedIngredient);
Console::WriteLine(L"Scoops: {0}", Scoops);
Console::WriteLine(L"Total Price: {0:C}\n", TotalPrice);
}
else
Console::WriteLine(L"The name you entered is not "
L"registered in our previous orders");
}
finally
{
bnrIceScream->Close();
stmIceScream->Close();
}
}
|
- Access the IceCream4.cpp source file and change it as follows:
// IceCream4.cpp : main project file.
#include "stdafx.h"
#include "IceCream.h"
using namespace System;
int main()
{
String ^ answer = L"n";
CIceCream ^ ic = gcnew CIceCream();
Console::Write(L"Do you want to re-order a previously "
L"saved order(y/n)? ");
answer = Console::ReadLine();
if( (answer == L"y") || (answer == L"Y") )
ic->OpenOrder();
else
{
ic->ProcessAnOrder();
Console::Write(L"Do you want us to remember this "
L"order the next time you come to "
L"get your ice scream (y/n)? ");
answer = Console::ReadLine();
if( (answer == L"y") || (answer == L"Y") )
ic->SaveOrder();
else
Console::WriteLine(L"\nIt was nice serving you."
L"\nCome Again!!!\n");
}
return 0;
}
|
- Execute the application and test it. Here is an example:
Do you want to re-order a previously saved order(y/n)? n
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Ice Scream Vending Machine
-----------------------------------
What type of flavor do you want?
1 - Vanilla
2 - Cream of Cocoa
3 - Chocolate Chip
4 - Organic Strawberry
5 - Butter Pecan
6 - Cherry Coke
7 - Chocolate Brownies
8 - Caramel Au Lait
9 - Chunky Butter
10 - Chocolate Cookie
Your Choice? 6
-----------------------------------
What type of container do you want?
1 - Cone
2 - Cup
3 - Bowl
Your Choice? 2
-----------------------------------
Do you want an ingredient or not
1 - No Ingredient
2 - Peanuts
3 - M & M
4 - Cookies
Your Choice? 1
-----------------------------------
How many scoops(1, 2, or 3)? 2
-----------------------------------
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Ice Scream Order
-----------------------------------
Flavor: Cherry Coke
Container: Cup
Ingredient: No Ingredient
Scoops: 2
Total Price: $2.60
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
Do you want us to remember this order the next time you
come to get your ice scream (y/n)? n
It was nice serving you.
Come Again!!!
Press any key to continue . . .
|
- Close the DOS window
- Execute the application and test it. Enter a wrong file name. Here is an
example:
Do you want to re-order a previously saved order(y/n)? y
Please enter the name you previously gave to remember your order: dtr
Unhandled Exception: System::IO.FileNotFoundException:
Could not find file 'C:\Do
cuments and Settings\Administrator\My Documents\
Visual Studio 2005\Projects\Vend
ingMachine4\IceCream4\bin\Release\dtr.icr'.
File name: 'C:\Documents and Settings\Administrator\
My Documents\Visual Studio 2
005\Projects\VendingMachine4\IceCream4\bin\Release\dtr.icr'
at System::IO.__Error.WinIOError(Int32 errorCode, String ^ maybeFullPath)
at System::IO.FileStream.Init(String ^ path,
FileMode mode, FileAccess access, I
nt32 rights, Boolean useRights, FileShare share,
Int32 bufferSize, FileOptions o
ptions, SECURITY_ATTRIBUTES secAttrs, String ^ msgPath, Boolean bFromProxy)
at System::IO.FileStream..ctor(String ^ path, FileMode mode)
at IceCream4.IceScream.OpenOrder() in
C:\Documents and Settings\Administrator
\My Documents\Visual Studio 2005\Projects\
VendingMachine4\IceCream4\IceScream.cs
:line 360
at IceCream4.Program.Main(String[] args) in
C:\Documents and Settings\Adminis
trator\My Documents\Visual Studio 2005\Projects\
VendingMachine4\IceCream4\Progra
m.cs:line 18
Press any key to continue . . .
|
- Close the DOS window
.NET Framework Exception Handling for File Processing
|
|
In the previous lesson of our introduction to file
processing, we behaved as if everything was alright. Unfortunately, file
processing can be very strict in its assignments. Fortunately, the .NET
Framework provides various Exception-oriented classes to deal with almost any
type of exception you can think of.
One of the most important aspects of file processing is the
name of the file that will be dealt with. In some cases you can provide this
name to the application or document. In some other cases, you would let the user
specify the name of the path. Regardless of how the name of the file would be
provided to the operating system, when this name is acted upon, the compiler
will be
asked to work on the file. If the file doesn't exist, the operation cannot be
carried. Furthermore, the compiler would throw an error. There are many other
exceptions that can be thrown as a result of something going bad during file
processing:
FileNotFoundException: The exception thrown when a
file has not been found is of type FileNotFoundException. Here is an example
of handling it:
using namespace System;
using namespace System::IO;
int main()
{
/* String ^ NameOfFile = L"Members.clb";
FileStream ^ fstPersons = gcnew FileStream(NameOfFile, FileMode::Create);
BinaryWriter ^ wrtPersons = gcnew BinaryWriter(fstPersons);
try
{
wrtPersons->Write(L"James Bloch");
wrtPersons->Write(L"Catherina Wallace");
wrtPersons->Write(L"Bruce Lamont");
wrtPersons->Write(L"Douglas Truth");
}
finally
{
wrtPersons->Close();
fstPersons->Close();
}*/
String ^ NameOfFile = L"Members.clc";
String ^ strLine = L"";
try {
FileStream ^ fstMembers =
gcnew FileStream(NameOfFile, FileMode::Open);
BinaryReader ^ rdrMembers = gcnew BinaryReader(fstMembers);
try {
strLine = rdrMembers->ReadString();
Console::WriteLine(strLine);
strLine = rdrMembers->ReadString();
Console::WriteLine(strLine);
strLine = rdrMembers->ReadString();
Console::WriteLine(strLine);
strLine = rdrMembers->ReadString();
Console::WriteLine(strLine);
}
finally
{
rdrMembers->Close();
fstMembers->Close();
}
}
catch (FileNotFoundException ^ ex)
{
Console::Write(L"Error: " + ex->Message);
Console::WriteLine(L" May be the file doesn't exist " +
L"or you typed it wrong!");
}
return 0;
}
Here is an example of what this would produce:
Error: Could not find file 'c:\Documents and Settings\Administrator
\My Documents\Visual Studio 2005\Projects\FileProcessing2
\FileProcessing2\Members.clc'. May be the file doesn't exist
or you typed it wrong!
Press any key to continue . . .
IOException: As mentioned already, during file
processing, anything could go wrong. If you don't know what caused an error, you
can throw the IOException exception.
Practical
Learning: Handling File Processing Exceptions |
|
- In the Scopes combo box, select CIceCream
- In the Functions combo box, select SaveOrder
- To throw exceptions, change the method as follows:
void CIceCream::SaveOrder(void)
{
String ^ strNameOfFile;
Console::Write(L"Please enter your initials or the name "
L"we will use to remember your order: ");
strNameOfFile = Console::ReadLine();
strNameOfFile = strNameOfFile + L".icr";
try {
// Find out if the user entered a name of a file
// that is already in the machine
if( File::Exists(strNameOfFile) )
{
String ^ answer;
FileStream ^ stmIceScream =
gcnew FileStream(strNameOfFile, FileMode::Create);
BinaryWriter ^ bnwIceScream =
gcnew BinaryWriter(stmIceScream);
try {
// If so, find out if the user wants to
// replace the old file
Console::WriteLine(L"The file you entered exists already.");
Console::Write(L"Do you want to replace it(y/n)?");
answer = Console::ReadLine();
// If the customer wants to replace it...
if( (answer == "y") || (answer == "Y") )
{
// ... do so
Console::WriteLine(L"The former order with the same "
L"name will be replaced");
Console::WriteLine(
L"\n=-= Ice Scream Vending Machine =-=");
Console::WriteLine(L" Saving Order: {0}", strNameOfFile);
bnwIceScream->Write(Flavor[ChoiceFlavor - 1]);
bnwIceScream->Write(Container[ChoiceContainer - 1]);
bnwIceScream->Write(Ingredient[ChoiceIngredient - 1]);
bnwIceScream->Write(Scoops);
bnwIceScream->Write(TotalPrice);
}
// If the customer wants to save the new order with
// a different name
else if( (answer == "n") || (answer == "N") )
{
// Ask the user to enter a name to remember the order
Console::Write(L"Please enter a name we will use "
L"to remember this order: ");
strNameOfFile = Console::ReadLine();
strNameOfFile = strNameOfFile + L".icr";
try {
stmIceScream =
gcnew FileStream(strNameOfFile, FileMode::Create);
bnwIceScream = gcnew BinaryWriter(stmIceScream);
Console::WriteLine(
L"\n=-= Ice Scream Vending Machine =-=");
Console::WriteLine(
L" Saving Order: {0}", strNameOfFile);
bnwIceScream->Write(Flavor[ChoiceFlavor - 1]);
bnwIceScream->Write(Container[ChoiceContainer - 1]);
bnwIceScream->Write(
Ingredient[ChoiceIngredient - 1]);
bnwIceScream->Write(Scoops);
bnwIceScream->Write(TotalPrice);
}
catch(IOException ^)
{
Console::Write(L"\nThe file you wanted us to "
L"create exists already. ");
Console::WriteLine(L"In case it was registered "
L"by a different customer, "
L"we will not delete it.");
}
}
else
Console::WriteLine(L"Invalid Answer - We will close");
}
catch(IOException ^)
{
Console::Write(L"\nThat file exists already. ");
Console::WriteLine(L"We need to preserve it just in "
L"case another customer will require it.");
}
finally
{
bnwIceScream->Close();
stmIceScream->Close();
}
}
else
{
FileStream ^ stmIceScream =
gcnew FileStream(strNameOfFile, FileMode::Create);
BinaryWriter ^ bnwIceScream =
gcnew BinaryWriter(stmIceScream);
try {
Console::WriteLine(L"\n=-= Ice Scream Vending Machine =-=");
Console::WriteLine(L" Saving Order: {0}", strNameOfFile);
bnwIceScream->Write(Flavor[ChoiceFlavor - 1]);
bnwIceScream->Write(Container[ChoiceContainer - 1]);
bnwIceScream->Write(Ingredient[ChoiceIngredient - 1]);
bnwIceScream->Write(Scoops);
bnwIceScream->Write(TotalPrice);
}
finally
{
bnwIceScream->Close();
stmIceScream->Close();
}
}
}
catch(IOException ^ ex)
{
Console::WriteLine(L"\nError: " + ex->Message);
Console::WriteLine(L"Operation Canceled: The file you want "
L"to create exists already.");
}
}
|
- In the Functions combo box, select OpenOrder
- To throw exceptions, change the method as follows:
void CIceCream::OpenOrder(void)
{
String ^ strNameOfFile;
String ^ SelectedFlavor;
String ^ SelectedContainer;
String ^ SelectedIngredient;
// Ask the user to enter a name of a previously saved order
Console::Write(L"Please enter the name you previously "
L"gave to remember your order: ");
strNameOfFile = Console::ReadLine();
strNameOfFile = strNameOfFile + ".icr";
try {
FileStream ^ stmIceScream =
gcnew FileStream(strNameOfFile, FileMode::Open);
BinaryReader ^ bnrIceScream =
gcnew BinaryReader(stmIceScream);
try {
// Find out if this order was previously saved in the machine
if( File::Exists(strNameOfFile) )
{
// If so, open it
SelectedFlavor = bnrIceScream->ReadString();
SelectedContainer = bnrIceScream->ReadString();
SelectedIngredient = bnrIceScream->ReadString();
Scoops = bnrIceScream->ReadInt32();
TotalPrice = bnrIceScream->ReadDouble();
// And display it to the user
Console::WriteLine(L"\n=-= Ice Scream Vending Machine =-=");
Console::WriteLine(L" Previous Order: {0}", strNameOfFile);
Console::WriteLine(L"Flavor: {0}", SelectedFlavor);
Console::WriteLine(L"Container: {0}", SelectedContainer);
Console::WriteLine(L"Ingredient: {0}", SelectedIngredient);
Console::WriteLine(L"Scoops: {0}", Scoops);
Console::WriteLine(L"Total Price: {0:C}\n", TotalPrice);
}
else
Console::WriteLine(L"The name you entered is not "
L"registered in our previous orders");
}
finally
{
bnrIceScream->Close();
stmIceScream->Close();
}
}
catch(FileNotFoundException ^ ex)
{
Console::Write(L"\nError: " + ex->Message);
Console::WriteLine(L"It is unlikely that the file exists in "
L"our machine's register.");
}
}
|
- Exercise the application and test it
- Close the DOS window
|
|