Build a RUST GUI App: Student Analyzer + CSV Export (using egui)

I’m excited to share this as my first post on the DEV Community! 🎉

💡 Want to build your first GUI app in Rust?
This post walks you through creating a Student Analyzer app using egui, with form inputs, grade logic, and CSV export — all in a beautiful GUI using the eframe crate!

🎯 What You’ll Build

A minimal yet functional GUI that:

✅ Accepts student details and marks

✅ Calculates average and pass/fail result

✅ Exports the data into a CSV file

🧱 App Structure

We build this using the eframe framework — a native GUI library powered by egui.

Main building blocks:

StudentApp struct – Core data model of GUI application
impl Default – Initial state of app at launch
impl eframe::App – Draws UI and handles logic

🧠 Code Breakdown – GUI + Logic

This code defines the app’s data model and initial state.

struct StudentApp{
    name: String,
    roll_no: String,
    subjects: Vec<String>,
    selected_subjects: [usize; 7],
    marks: [String; 7],
    average: Option<f32>,
    result: Option<String>,
}

impl Default for StudentApp {
    fn default() -> Self {
        Self {
            name: String::new(),
            roll_no: String::new(),
            subjects: vec![
                "Math".to_string(),
                "Science".to_string(),
                "English".to_string(),
                "Social".to_string(),
                "Computer".to_string(),
                "Hindi".to_string(),
                "Tamil".to_string(),
            ],
            selected_subjects: [0; 7],
            marks: Default::default(),
            average: None,               
            result: None,
        }
    }
}

And

In impl eframe::App, the update() function gets called repeatedly while your app is running.
Inside this function, we:

Create a window (CentralPanel) where the UI lives.
Add form fields for user input (like name, roll number, subjects, marks).
Handle logic for computing average and result.
Render the result to the user.

🔖 Code Purpose Table (Highlight View)

Purpose	Explanation
`TextEdit::singleline(...)`	Draws input box for user text
`ui.button("Add Marks")`	Adds current mark to the list
`calculate_result()`	Computes average and pass/fail
`write_to_csv()`	Appends form data to a CSV file
`egui::CentralPanel::default().show(...)`	Main layout container of the UI with title centered
`egui::ComboBox::from_id_source(...)`	Renders subject dropdown for each entry

📤 CSV Export Logic

This snippet writes the data by saving each student's entry into a CSV file for future use or reporting.

                            let file_path = "student_analyzer.csv";
                            let file_exists = std::path::Path::new(file_path).exists();
                            let file = OpenOptions::new()
                                .create(true)
                                .append(true)
                                .open(file_path)
                                .expect("Cannot open file");

✨ Preview Screens

💻 Input Form

The StudentApp screen at launch, with fields for name, subject, and marks.

📊 Average + Result View

The user adds multiple marks, and the app calculates the average and displays the result.

📁 CSV Export Confirmation

A student_analyzer.csv file stores the entered data persistently for later use.

📎 Try the Full App
👉 Full post with detailed explanations and setup steps:
🔗 Techn0tz Full Blog

Source code
👉 Download the Student Analyzer Rust code

💭 What’s Next?
In the next post, test your Rust foundations with a quick interactive Mini Quiz on Techn0tz!

Thanks for reading! 🌱
This is my first post on DEV, and I'm truly excited to be part of this amazing community. If you found it helpful or have suggestions, feel free to drop a comment or connect! 🚀-Techn0tz

manjushaps @manjushaps