CODEWITHSUNDEEP
gtkrustlifetime
Boiethios
Boiethios

Reputation: 42909

How to use the button itself from the callback closure?

I have written this little code from gtk-rs examples, but it cannot compile since the button cannot be used from the closure.

extern crate gtk;

use gtk::prelude::*;

fn main() {
    if gtk::init().is_err() {
        println!("Failed to initialize GTK.");
        return;
    }
    let window = gtk::Window::new(gtk::WindowType::Toplevel);
    let button = gtk::Button::new_from_stock("Click me !");

    window.add(&button);

    window.connect_delete_event(|_, _| {
        gtk::main_quit();
        Inhibit(false)
    });

    button.connect_clicked(move |_| {
        button.hide(); // error
    });

    window.show_all();
    gtk::main();
}

The compiler writes:

src/main.rs:22:3: 22:9 error: cannot move `button` into closure because it is borrowed [E0504]
src/main.rs:22      button.hide();
                    ^~~~~~
src/main.rs:21:2: 21:8 note: borrow of `button` occurs here
src/main.rs:21  button.connect_clicked(move |_| {
            ^~~~~~

How to solve this problem?

I cannot pass variables by reference: it is invalid because the lifetime of closure may exceed the lifetime of main, compiler says.

Note: I use this Cargo.toml to compile:

[package]
name = "test"
version = "0.1.0"
authors = ["Me"]

[features]
default = ["gtk/v3_16"]

[dependencies]
gtk = { git = "https://github.com/gtk-rs/gtk.git" }

Upvotes: 2

Views: 359

Answers (1)

Jussi Kukkonen
Jussi Kukkonen

Reputation: 14617

underscore doesn't mean "same name as outside the closure", it means "make the closure argument unused/unusable". Try naming the argument:

button.connect_clicked(move |button| {
    button.hide();
});

Upvotes: 3

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