Struct NavController 

pub struct NavController {
    pub push: Box<dyn Fn(&str) -> bool>,
    pub pop: Box<dyn Fn(bool) -> bool>,
    pub current: Box<dyn Fn() -> String>,
    pub enter: Box<dyn Fn(&str) -> bool>,
    pub segments: Box<dyn Fn() -> Vec<String>>,
}

A mounted host’s control surface. Closures run user code (route builders), so the registry NEVER holds a borrow across a call (§3.3 discipline: clone the Rc out, then call).

Fields

push: Box<dyn Fn(&str) -> bool>

Push (or, in split/tab presentation, select) a registered route. False = unknown route.

pop: Box<dyn Fn(bool) -> bool>

Pop the top route. already_popped = the native side popped first (iOS back). False = nothing to pop (tabs hosts always return false: they have no stack).

current: Box<dyn Fn() -> String>

Current route path (“” while showing the root).

enter: Box<dyn Fn(&str) -> bool>

Consume one segment of an ABSOLUTE path. Selectors/tabs accept a declared key (same as push); a stack accepts ANY segment by pushing it (its destinations are open-ended). Distinct from push so a relative navigate("key") can still fall through a stack.

segments: Box<dyn Fn() -> Vec<String>>

This surface’s contribution to the full route: [] at root, [key] for a selector / tabs, the whole path for a stack.