Temporary value dropped while borrowed using Closure

[tostaylo]

To solve this error
"the size for values of type (dyn std::ops::Fn() + 'static) cannot be known at compilation time"

I added on_click: Option<&'static dyn Fn() -> ()>

But now I am unsure how to solve
"temporary value dropped while borrowed"

fn main(){
let initial_state = 5;
fn handler(val: i32) {
       val + 1;
       ()
   }
   
let props = Props { on_click: Some(&|| handler(initial_state))};
}

struct Props {
   on_click: Option<&'static dyn Fn() -> ()>
}

How do I make initial_state live long enough?

[alice]

By using &'static you are telling the compiler that the closure must be an immutable compile time constant, so you can't store a local variable such as initial_state inside it. Use a Box instead.

struct Props {
   on_click: Option<Box<dyn Fn() -> ()>>
}

[RustyYato]

You will probably also need to annotaye your closure with move

move || handler(initial_state)

If you want to see how closures are desugared, you can read my blog on the subject:

Closures: Magic Functions

[tostaylo]

@RustyYato Thank you, I will read your blog on closures. I am working with the wasm crate right now and am running into many issues regarding closures and lifetime's.