Data model
- C++ course
- Beginner
- Lesson 113/116
- 6 min
Set up the structs and vectors for the app.
Task struct and vector
In the task list app, we will define a Task struct to represent each task. This struct will have two fields: title and status. We will use a vector<Task> to hold all tasks.
vector<T> is a container that provides a dynamic array in C++. You add items with push_back and access them with [index]. In this lesson we will add the Task struct, a vector called tasks, and the first task.
Using vector<Task>
The declaration vector<Task> creates a dynamic list of tasks. You add a new task with push_back and access an existing one with [index]. The #include <vector> header is required.
vector<Task> tasks;
Task t;
t.title = "Homework";
t.status = "pending";
tasks.push_back(t);
cout << tasks[0].title;Here tasks[0] is the first task; its fields are accessed with .title and .status. This pattern forms the basic data model of the task list.
Practice Add the Task struct and vector
Add the #include <vector> and #include <string> headers. Define struct Task { string title; string status; };. In main, after printMenu();, create vector<Task> tasks;, build Task t; with t.title = "Homework"; and t.status = "pending";, add it with tasks.push_back(t);. Print cout << tasks[0].title << " - " << tasks[0].status << endl;.
Starter code
#include <iostream>
#include <string>
#include <vector>
using namespace std;
void printMenu() {
cout << "1 - Add" << endl;
cout << "2 - List" << endl;
cout << "3 - Exit" << endl;
}
// Define the Task struct
int main() {
printMenu();
// build a Task, add it to a vector, print
return 0;
}Sample solution
#include <iostream>
#include <string>
#include <vector>
using namespace std;
void printMenu() {
cout << "1 - Add" << endl;
cout << "2 - List" << endl;
cout << "3 - Exit" << endl;
}
struct Task {
string title;
string status;
};
int main() {
printMenu();
vector<Task> tasks;
Task t;
t.title = "Homework";
t.status = "pending";
tasks.push_back(t);
cout << tasks[0].title << " - " << tasks[0].status << endl;
return 0;
}Expected output
1 - Add 2 - List 3 - Exit Homework - pending
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Fill in the blank: Task member
struct Task {
string title;
string ____;
};struct Task {
string title;
string status;
};Explanation: The status field holds the task's status.
2 Which header is required for vector<Task>?
- <string>
- <vector> Correct answer
- <list>
- <array>
Explanation: vector comes with the <vector> header.
3 Match each field with its type
| Term | Meaning |
|---|---|
title |
title text |
status |
status text |
vector<Task> |
task list |