I am trying to do a get a object from a database with Diesel when the Enter key is pressed in a gtk Entry. My idea is to create a Diesel SQLite connection in main function and then borrow it every time that I need it.
To do that, I am trying to use a very simple MVC. The idea is to pass the connection to all the controllers and reuse it. I know that lifetime is necessary here.
pub struct Controller<'a> {
pub connection: &'a SQLiteConnection,
pub search_entry: SearchEntry,
....
}
impl<'a> Controller<'a> {
pub fn new(conn: &'a SQLiteConnection) -> Self {
Self {
search_entry: SearchEntry::new(),
connection: conn,
....
}
}
pub fn init(&self) {
self.search_entry.connect_activate(|x| {
let need_it = diesel_table
.filter(column_id.eq(&x.get_text().unwrap()))
.first(self.connection)
.unwrap();
});
}
}
When compile I get this:
error[E0495]: cannot infer an appropriate lifetime due to conflicting requirements
--> src/lib.rs:44:44
|
44 | self.search_entry.connect_activate(|x| {
| ____________________________________________^
45 | | let need_it = diesel_table
46 | | .filter(column_id.eq(&x.get_text().unwrap()))
47 | | .first(self.connection)
48 | | .unwrap();
49 | | });
| |_________^
|
note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the method body at 43:5...
--> src/lib.rs:43:5
|
43 | / pub fn init(&self) {
44 | | let need_it = diesel_table
46 | | .filter(column_id.eq(&x.get_text().unwrap()))
47 | | .first(self.connection)
48 | | .unwrap();
49 | | });
50 | | }
| |_____^
note: ...so that the types are compatible
--> src/lib.rs:44:44
|
44 | self.search_entry.connect_activate(|x| {
| ____________________________________________^
45 | | let need_it = diesel_table
46 | | .filter(column_id.eq(&x.get_text().unwrap()))
47 | | .first(self.connection)
48 | | .unwrap();
49 | | });
| |_________^
= note: expected `&&Controller<'_>`
found `&&Controller<'a>`
= note: but, the lifetime must be valid for the static lifetime...
note: ...so that the type `[closure@src/lib.rs:44:44: 49:10 self:&&Controller<'_>]` will meet its required lifetime bounds
--> src/lib.rs:44:27
|
44 | self.search_entry.connect_activate(|x| {
| ^^^^^^^^^^^^^^^^
This error is because the function connect_activate has a static parameter: fn connect_activate<F: Fn(&Self) + 'static>.
I would not like to initialize the connection every time that the user press the Intro key by using a function that returns a connection. Instead I would like to borrow that connection.
What would be the most efficient way to do that?
Thanks you very much. I hope you understand everything.
I think you need a Rc<SQLiteConnection>