Although you can write your own routines to perform these operations, the Array class provides most of the methods you would need to get the necessary information.
We have seen that, using the [] operator, you can add a new element to an array. Still, to support this operation, the Array class is equipped with the SetValue() method that is overloaded with various versions. Here is an example that adds an element to the third position of the array:
File: Exercise.h #pragma once
#include "Person.h"
using namespace System;
using namespace System::ComponentModel;
using namespace System::Collections;
using namespace System::Windows::Forms;
using namespace System::Data;
using namespace System::Drawing;
namespace Exercise1 {
/// <summary>
/// Summary for Exercise
///
/// WARNING: If you change the name of this class, you will need to change the
/// 'Resource File Name' property for the managed resource compiler tool
/// associated with all .resx files this class depends on. Otherwise,
/// the designers will not be able to interact properly with localized
/// resources associated with this form.
/// </summary>
public ref class Exercise : public System::Windows::Forms::Form
{
array<CPerson ^> ^ People;
array<CPerson ^> ^ ArrayInitializer();
void ShowPeople(array<CPerson ^> ^ People);
public:
Exercise(void)
{
InitializeComponent();
//
//TODO: Add the constructor code here
//
}
protected:
/// <summary>
/// Clean up any resources being used.
/// </summary>
~Exercise()
{
if (components)
{
delete components;
}
}
. . . No Change
private:
/// <summary>
/// Required designer variable.
/// </summary>
System::ComponentModel::Container ^components;
#pragma region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
void InitializeComponent(void)
{
. . . No Change
}
#pragma endregion
private: System::Void Exercise_Load(System::Object^ sender, System::EventArgs^ e)
{
array<CPerson ^> ^ persons = ArrayInitializer();
ShowPeople(persons);
}
private: System::Void btnAdd_Click(System::Object^ sender, System::EventArgs^ e)
{
CPerson ^ pers = gcnew CPerson;
pers->PersonID = int::Parse(txtPersonID->Text);
pers->FirstName = txtFirstName->Text;
pers->LastName = txtLastName->Text;
if (cbxGenders->Text == L"Male")
pers->Gender = L"Male";
else if (cbxGenders->Text == L"Female")
pers->Gender = L"Female";
else
pers->Gender = L"Unknown";
People->SetValue(pers, pers->PersonID);
ShowPeople(People);
}
};
}
File: Exercise.cpp #include <windows.h>
#include "Exercise.h"
namespace Exercise1
{
array<CPerson ^> ^ Exercise::ArrayInitializer()
{
People = gcnew array<CPerson ^>(8);
for(int i = 0; i < 8; i++)
{
People[i] = gcnew CPerson;
People[i]->PersonID = 0;
People[i]->FirstName = L"";
People[i]->LastName = L"";
People[i]->Gender = L"Unknown";
}
return People;
}
void Exercise::ShowPeople(array<CPerson ^> ^ People)
{
lvwPeople->Items->Clear();
for each(CPerson ^ pers in People)
{
ListViewItem ^ lviPerson =
gcnew ListViewItem(pers->PersonID->ToString());
lviPerson->SubItems->Add(pers->FirstName);
lviPerson->SubItems->Add(pers->LastName);
lviPerson->SubItems->Add(pers->Gender);
lvwPeople->Items->Add(lviPerson);
}
}
}
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow)
{
Application::Run(gcnew CExercise1::Exercise);
return 0;
}
When the Array::SetValue() method is called, it replaces the element at the indicated position.
The reverse of adding an item to an array is to retrieve one. You can do this with the [] operator. To support this operation, the Array class is equipped with the GetValue() method that comes in various versions. Here is an example of calling it: System::Void lvwPeople_ItemSelectionChanged(System::Object^ sender,
System::Windows::Forms::ListViewItemSelectionChangedEventArgs^ e)
{
CPerson ^ pers = static_cast<CPerson ^>(People->GetValue(e->ItemIndex));
txtPersonID->Text = pers->PersonID->ToString();
txtFirstName->Text = pers->FirstName;
txtLastName->Text = pers->LastName;
cbxGenders->Text = pers->Gender->ToString();
}
When calling this method, make sure you provide a valid index, if you do not, you would get an IndexOutOfRangeException exception. |
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Practical
Learning: Introducing Operations on Arrays
