CODEWITHSUNDEEP
rust
Stents
Stents

Reputation: 71

Cannot pass self as callback parameter due to double borrowing

I'm trying to call closure that was saved inside a struct but I'd also like to pass the struct as an argument to the closure. Here's the specific piece of code.

pub fn react(&mut self) -> &mut Button {
   if let Some(ref mut c) = self.click_callback {
            c(self);
    }
    self
}

Note that self is a Button and self.click_callback is an Option<Box<Fn(&mut Button)>>

So from what I understand the "if let" borrows self until its scopes ends, but then when I try to pass self as an argument it attempts to borrow it again. Is there anything specific I can do that will avoid this double borrow attempt?

Upvotes: 7

Views: 517

Answers (1)

DK.
DK.

Reputation: 58975

The simplest solution is to break the callback out from self, like so:

let callback = self.click_callback.take();
if let Some(ref mut c) = callback {
    c(self);
}
self.click_callback = callback;
self

This temporarily replaces click_callback with None, hence why you have to put it back when you're done.

Upvotes: 8

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