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YBStatechart is a statechart framework. Statecharts are a formalized type of finite state machine, which resulted from [David Harel's research] 1 on software architecture design for aircraft systems in 1986. His [white paper article] 1 is well worth the (somewhat lengthy) read.

The statechart design pattern is also used in the SproutCore web front-end framework. They wrote [a blog article] 2 about statecharts compared to the model-view-controller pattern.

Contrived example

A very simple example of a chart with only 2 substates:

YBState *rootState = [YBState stateWithName:@"rootState"];
YBState *loggedOut = [YBState stateWithName:@"loggedOut"];
YBState *loggedIn = [YBState stateWithName:@"loggedIn"];

[loggedIn onEnterState:^(YBState *_self) {
    // executed when loggedIn state is entered / activated

[loggedIn onExitState:^(YBState *_self) {
    // executed when loggedIn state is exited / deactivated

[loggedIn on:@"buttonPress" doBlock:^(YBState *_self) {
    // executed only when loggedIn is active
	// AND 
	// [statechart buttonPress] or [statechart dispatchEvent:@"buttonPress"] got called

YBStatechart *statechart = [[YBStatechart alloc] init];
statechart.rootState = rootState;
[statechart activate];

A state can be activated by calling one of the -activateState...: methods on the statechart, e.g.:

[statechart activateState:loggedIn];

Now the statechart object is able to respond to arbitrary Objective-C messages, which will be dispatched as "events" to all the active substates and their active substates, ... For example:

[statechart buttonPress];

This will call the block handlers associated with the named event buttonPress, but only on states that are active at this moment.

For more useful examples, please read [David Harel's white paper] 1.


CocoaPods is the recommended way to install YBStatechart

Example podfile:

pod 'YBStatechart'


YBLStatechart is licensed under the Apache Software License, 2.0 ("Apache 2.0")

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