book: Move to std::cell::OnceCell (#1470)

Hofer-Julian · web-flow · commit d0d41104aa6e · 2023-08-16T10:10:36.000+02:00
diff --git a/book/listings/actions/7/window/imp.rs b/book/listings/actions/7/window/imp.rs
@@ -2,7 +2,7 @@ use gio::Settings;
 use glib::subclass::InitializingObject;
 use gtk::subclass::prelude::*;
 use gtk::{gio, glib, Button, CompositeTemplate, Label};
-use once_cell::sync::OnceCell;
+use std::cell::OnceCell;
 
 // ANCHOR: imp_struct
 // Object holding the state
diff --git a/book/listings/saving_window_state/1/custom_window/imp.rs b/book/listings/saving_window_state/1/custom_window/imp.rs
@@ -1,7 +1,7 @@
 use gio::Settings;
 use gtk::subclass::prelude::*;
 use gtk::{gio, glib, ApplicationWindow};
-use once_cell::sync::OnceCell;
+use std::cell::OnceCell;
 
 // ANCHOR: imp
 #[derive(Default)]
diff --git a/book/listings/todo/2/window/imp.rs b/book/listings/todo/2/window/imp.rs
@@ -6,7 +6,7 @@ use glib::subclass::InitializingObject;
 use gtk::prelude::*;
 use gtk::subclass::prelude::*;
 use gtk::{gio, glib, CompositeTemplate, Entry, ListView};
-use once_cell::sync::OnceCell;
+use std::cell::OnceCell;
 
 use crate::task_object::{TaskData, TaskObject};
 use crate::utils::data_path;
diff --git a/book/listings/todo/3/window/imp.rs b/book/listings/todo/3/window/imp.rs
@@ -6,7 +6,7 @@ use glib::subclass::InitializingObject;
 use gtk::prelude::*;
 use gtk::subclass::prelude::*;
 use gtk::{gio, glib, CompositeTemplate, Entry, ListView};
-use once_cell::sync::OnceCell;
+use std::cell::OnceCell;
 
 use crate::task_object::{TaskData, TaskObject};
 use crate::utils::data_path;
diff --git a/book/listings/todo/4/window/imp.rs b/book/listings/todo/4/window/imp.rs
@@ -6,7 +6,7 @@ use glib::subclass::InitializingObject;
 use gtk::prelude::*;
 use gtk::subclass::prelude::*;
 use gtk::{gio, glib, CompositeTemplate, Entry, ListView};
-use once_cell::sync::OnceCell;
+use std::cell::OnceCell;
 
 use crate::task_object::{TaskData, TaskObject};
 use crate::utils::data_path;
diff --git a/book/listings/todo/5/window/imp.rs b/book/listings/todo/5/window/imp.rs
@@ -6,7 +6,7 @@ use glib::subclass::InitializingObject;
 use gtk::prelude::*;
 use gtk::subclass::prelude::*;
 use gtk::{gio, glib, CompositeTemplate, Entry, ListView};
-use once_cell::sync::OnceCell;
+use std::cell::OnceCell;
 
 use crate::task_object::{TaskData, TaskObject};
 use crate::utils::data_path;
diff --git a/book/listings/todo/6/window/imp.rs b/book/listings/todo/6/window/imp.rs
@@ -8,7 +8,7 @@ use glib::subclass::InitializingObject;
 
 use adw::prelude::*;
 use gtk::{gio, glib, CompositeTemplate, Entry, ListBox};
-use once_cell::sync::OnceCell;
+use std::cell::OnceCell;
 
 use crate::task_object::{TaskData, TaskObject};
 use crate::utils::data_path;
diff --git a/book/listings/todo/7/window/imp.rs b/book/listings/todo/7/window/imp.rs
@@ -8,7 +8,7 @@ use glib::subclass::InitializingObject;
 
 use adw::prelude::*;
 use gtk::{gio, glib, CompositeTemplate, Entry, ListBox};
-use once_cell::sync::OnceCell;
+use std::cell::OnceCell;
 
 use crate::task_object::{TaskData, TaskObject};
 use crate::utils::data_path;
diff --git a/book/listings/todo/8/collection_object/imp.rs b/book/listings/todo/8/collection_object/imp.rs
@@ -4,7 +4,7 @@ use adw::prelude::*;
 use adw::subclass::prelude::*;
 use glib::Properties;
 use gtk::{gio, glib};
-use once_cell::sync::OnceCell;
+use std::cell::OnceCell;
 
 // ANCHOR: collection_object
 // Object holding the state
diff --git a/book/listings/todo/8/window/imp.rs b/book/listings/todo/8/window/imp.rs
@@ -10,7 +10,7 @@ use gtk::glib::SignalHandlerId;
 use gtk::{
     gio, glib, Button, CompositeTemplate, Entry, FilterListModel, ListBox, Stack,
 };
-use once_cell::sync::OnceCell;
+use std::cell::OnceCell;
 
 use crate::collection_object::{CollectionData, CollectionObject};
 use crate::utils::data_path;
diff --git a/book/src/actions.md b/book/src/actions.md
@@ -251,7 +251,7 @@ Filename: <a class=file-link href="https://github.com/gtk-rs/gtk4-rs/blob/master
 
 Again, we install the schema as described in the settings [chapter](./settings.html).
 Then we add the settings to `imp::Window`.
-Since [`gio::Settings`](https://gtk-rs.org/gtk-rs-core/stable/latest/docs/gio/struct.Settings.html) does not implement `Default`, we wrap it in a [`once_cell::sync::OnceCell`](https://docs.rs/once_cell/latest/once_cell/sync/struct.OnceCell.html).
+Since [`gio::Settings`](https://gtk-rs.org/gtk-rs-core/stable/latest/docs/gio/struct.Settings.html) does not implement `Default`, we wrap it in a [`std::cell::OnceCell`](https://doc.rust-lang.org/std/cell/struct.OnceCell.html).
 
 Filename: <a class=file-link href="https://github.com/gtk-rs/gtk4-rs/blob/master/book/listings/actions/7/window/imp.rs">listings/actions/7/window/imp.rs</a>
 
diff --git a/book/src/g_object_signals.md b/book/src/g_object_signals.md
@@ -30,7 +30,9 @@ The advantage of `connect_closure` is that it also works with custom signals.
 
 Let's see how we can create our own signals.
 Again we do that by extending our `CustomButton`.
-First we override the necessary methods in `ObjectImpl`.
+First we override the `signals` method in `ObjectImpl`.
+In order to do that, we need to lazily initialize a static item `SIGNALS`.
+Until [`std::sync::LazyLock`](https://doc.rust-lang.org/std/sync/struct.LazyLock.html) is stabilized, we use [`once_cell::sync::Lazy`](https://docs.rs/once_cell/latest/once_cell/sync/struct.Lazy.html) instead.
 
 Filename: <a class=file-link href="https://github.com/gtk-rs/gtk4-rs/blob/master/book/listings/g_object_signals/2/custom_button/imp.rs">listings/g_object_signals/2/custom_button/imp.rs</a>
 
diff --git a/book/src/saving_window_state.md b/book/src/saving_window_state.md
@@ -27,14 +27,8 @@ Filename: <a class=file-link href="https://github.com/gtk-rs/gtk4-rs/blob/master
 > When creating new GObjects, this is nicer than calling the setter methods manually.
 
 The implementation struct holds the `settings`.
-You can see that we embed `Settings` in [`once_cell::sync::OnceCell`](https://docs.rs/once_cell/latest/once_cell/sync/struct.OnceCell.html).
-This is a nice alternative to `RefCell<Option<T>>` when you know that you will only write to it once. 
-`once_cell` is already part of Rust nightly.
-Until it hits stable, we will add it as external dependency.
-
-```
-cargo add once_cell
-```
+You can see that we embed `Settings` in [`std::cell::OnceCell`](https://doc.rust-lang.org/std/cell/struct.OnceCell.html).
+This is a nice alternative to `RefCell<Option<T>>` when you know that you will initialize the value only once. 
 
 We also override the `constructed` and `close_request` methods, where we load or save the window state. 
 
