You read names from the standard input stream and create Person objects in an indefinite while loop:
while(true)
{
Console::Write(L”Enter a first name or press Enter to end: “);
first = Console::ReadLine();
if(first->Length == 0)
break;
Console::Write(L”Enter a second name: “);
second = Console::ReadLine();
person = gcnew Person(first->Trim(),second->Trim());
people->push_back(person);
}
After prompting for the input, the Console::ReadLine() function reads a name from the standard
input stream and stores it in
first. If just the Enter key was pressed, the length of the string will be
zero so you test for this to decide when to exit the loop. If the first name read is not of zero length, you
read the second name. You then create a
Person object on the CLR heap and store the handle in person.
For each
String^ argument to the constructor, you call the Trim() function to remove any leading or
trailing spaces. Calling the
push_back() function for the people container stores the person handle in
the vector.
The objects exist independently of the container, so if you were to discard the container (by assigning
nullptr to people for example) it would not necessarily destroy the objects pointed to by the handles
it contains. In our example, we do not retain any handles to the objects, so in this case destroying the
container would result in the objects not being referenced anywhere so eventually the garbage collector
would get around to destroying them and freeing the memory they occupy on the CLR heap.
After the input loop ends, you output the contents of a vector in a
for each loop:
for each(Person^ person in people)
Console::WriteLine(“{0}”,person);
The for each loop works directly with sequence containers so you can use this to iterate over all the
handles stored in the
people vector. The Console::WriteLine() function calls the ToString()
function for each Person object to produce the string to be inserted in the first argument string.
It is not normal usage but let’s look at another working example to explore how you can store
ref class
objects in a sequence container, rather than handles.
Try It Out Storing Reference Class Objects in a Double-Ended Queue
You will use Person object again but this time you will sort the contents of the container before you
generate the output. Here’s the new version of the
Person class:
// Person.h
// A class defining a person
#pragma once
680
Chapter 10: The Standard Template Library
25905c10.qxd:WroxPro 2/21/08 9:11 AM Page 680
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