UXTransition

UXTransition is one edge in a UXStateMachine.

#use <UXKit>            // or #import "UXStateMachine.xc"

Overview

class UXTransition : Object {
    u8* fromState;
    u8* event;
    u8* toState;
}

m.addTransition((u8*)"welcome", (u8*)"next", (u8*)"details");

A transition is three strings. The flow is the set of transitions.

The edges are the rules

A machine holds only transitions, so what is not declared cannot happen. An event with no matching transition from the current state is refused, and this is not an error. A rule such as “you cannot go forward from the last page” is the absence of an edge, with no check elsewhere.

For this reason canFire is enough to drive a button’s enabled state, and adding a step to a wizard is an addTransition call with no edits to the screens.

Everything is a string, and nothing is registered

States and events are names you invent. There is no enumeration and no declaration step, so:

a typo is a state that never matches. There is no compile error or runtime error; the edge never fires.
the same name in two places is the same state, so a flow can be assembled from separate pieces

Keeping the names in one place, such as a header of literals, gives most of the benefit of an enum without the machine knowing about it.

Reading one back

UXTransition* t = m.transitionFor((u8*)"next");
if (t != (UXTransition*)0) { label.setText(t.toState); }

transitionFor returns the edge that an event would take. A Next button can use it to show where it leads as well as whether it is enabled.

A flow can also inspect itself this way: a diagram of a wizard is a walk over its transitions.

Fields

fromState

u8* fromState

event

u8* event

toState

u8* toState

All three are kept, not copied. Pass literals, or strings that outlive the machine.

Conforms to

Inherits Object