As stated already, to start creating an indexer, declare an array as a field. Here is an example:
In the body of the class, create a property named default that is an array. The property must take a parameter as an array. This means that it must have square brackets. Inside of the brackets, include the parameter you will use as index to access the members of the array. You usually access the members of an array using an integer-based index. Therefore, you can use an int type as the index of the array. Of course, the index's parameter must have a name, such as i. This would be done as follows: #pragma once
#include "Person.h"
ref class CPersons
{
public:
CPersons(void);
array<CPerson ^> ^ individual;
property CPerson ^ default[int i]
{
}
};
If you want the property to be read-only, include only a get accessor. In the get accessor, you should return an element of the array field the property refers to, using the parameter of the property. This would be done as follows: #pragma once
#include "Person.h"
ref class CPersons
{
public:
CPersons(void);
array<CPerson ^> ^ individual;
property CPerson ^ default[int]
{
CPerson ^ get(int i)
{
return individual[i];
}
}
};
If you want to create an indexer that can only receive values, add a set accessor only. If you want to create an indexed property that can both receive values and provide values, that is, if you want to create a read/write indexed property, create both a get and a set accessors. Here is an example: #pragma once
#include "Person.h"
ref class CPersons
{
public:
CPersons(void);
array<CPerson ^> ^ individual;
property CPerson ^ default[int]
{
CPerson ^ get(int i)
{
return individual[i];
}
void set(int i, CPerson ^ p)
{
individual[i] = p;
}
}
};
After creating a read/write indexer, you can assign its values outside of the class. In other words, clients of the class can change the values to its elements. Remember that the advantage of an indexed property is that each element of the arrayed field can be accessed from the instance of the class by directly applying the square brackets and the (appropriate) index to it. Here is an example: System::Void Exercise_Load(System::Object^ sender, System::EventArgs^ e)
{
CPersons ^ People = gcnew CPersons;
People[0] = gcnew CPerson;
People[0]->PersonID = 72947;
People[0]->Gender = L"Female";
People[0]->FirstName = L"Paulette";
People[0]->LastName = L"Cranston";
People[1] = gcnew CPerson;
People[1]->PersonID = 70854;
People[1]->Gender = L"Male";
People[1]->FirstName = L"Harry";
People[1]->LastName = L"Kumar";
People[2] = gcnew CPerson;
People[2]->PersonID = 27947;
People[2]->Gender = L"Male";
People[2]->FirstName = L"Jules";
People[2]->LastName = L"Davidson";
People[3] = gcnew CPerson;
People[3]->PersonID = 62835;
People[3]->Gender = L"Unknown";
People[3]->FirstName = L"Leslie";
People[3]->LastName = L"Harrington";
People[4] = gcnew CPerson;
People[4]->PersonID = 92958;
People[4]->Gender = L"Male";
People[4]->FirstName = L"Ernest";
People[4]->LastName = L"Colson";
for (int i = 0; i < 5; i++ )
{
ListViewItem ^ lviPerson = gcnew ListViewItem(People[i]->PersonID.ToString());
lviPerson->SubItems->Add(People[i]->FirstName);
lviPerson->SubItems->Add(People[i]->LastName);
lviPerson->SubItems->Add(People[i]->Gender->ToString());
lvwPeople->Items->Add(lviPerson);
}
}
This would produce:
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