Introduction

obj-behaviortree is an implementation of a behavior tree for iOS. Supported tasks include:

• Selector
• Sequence
• Concurrent
• Condition

Behavior trees can be built programatically, or by reading from a JSON file.

Requirements

The project currently builds and runs successfully with:

• Xcode 4.5
• iOS 5.0+

Setup

Clone the repository to a location on your machine, then:

$ git submodule init
$ git submodule update

Open BehaviorTree.xcworkspace

Test scenarios are available in the BehaviorTree project, which can be run in the usual way (CMD+U).

A demo project is available in the BehaviorTreeDemo project.

JSON Reader

A behavior tree can be built from a JSON representation:

{"type":"Selector","children":[
    {"type":"ShouldFlee","task":
    	{"type":"Flee"}
	},
	{"type":"ShouldSeek":"task":
		{"type":"Seek"}
	}
]}

The JSON is read by AOBehaviorReader which builds an instance of AOBehaviorTree:

NSString *json;
...
AOBehaviorReader *reader = [[AOBehaviorReader alloc] init];
AOBehaviorTree *behavior = [reader buildTreeWithFile:json];

The reader supports setting properties on task instances:

{"type":"MyAction","someBoolean":true}

If you want to set a property of type "Class", you can use the syntax:

{"type":"Flee","fromClassType":"class:MyEnemy"}

Task Class Prefixes

Task types read in from JSON are used to instantiate an objective-c class. To avoid polluting the JSON with class prefixes, you can register your own class prefixes that will be automatically searched when attempting to instantiate a task.

For example, if you register the prefix "AB" with the BehaviorReader:

AOBehaviorReader *reader = [[AOBehaviorReader alloc] init];
[reader registerPrefix:@"AB"];

and your JSON contains the task:

{"type":"MyTask"}

then the BehaviorReader will first attempt to find a class named "MyTask", and then if that class does not exist it will attempt to find a class named "ABMyTask".

Logging

Logging can be enabled by setting preprocessor macro flags on the BehaviorTree target.

BTree_NSLog

Logs to console window using standard NSLog

BTree_NSLogger

Logs to an NSLogger client using the NSLogger client library, which is much faster than using NSLog.