Cross-platform developmentfor

iPhone

Contributor: Tovchenko Taras(Doctor Set)

Plan

• What is cross-platform development

• Benefits & Expenses

• Implementation - 2 ways

• Use open source libraries

• A&Q

What does this mean “cross-platform”?

2. Business logic 1. GUI

GUI porting is very bag applicable from iPhone to desktop platforms

- ?

How we can distribute business logic?

1. Base logic - memory, containers, etc.

2. Logic of your application

3. Graphic output (OpenGL, convertors)

4. Audio output (OpenAL)

5. Databases

What applications we can create full cross-platform and what can be created

particles?

1. (Full) Games - 60% at all iPhone applications

2. (Medium) Scientific applications which use graphic output - medical, engineering, etc.

3. (Not applicable) Applications based on iPhone GUI

Expenses1. If you write 2 applications = you pay x2 $

2. Or you can write 1 application for 2 markets = x1.1 - x1.7 $

Several paths for attainment cross-platform

• Porting existing code

• Write new code than will be oriented to cross-platform

PortingIf you have already wrote project - use this method

Problems

1. Existing code wrote on language which not compile on other platforms, often this is Objective-C

2. On a project was used system depended api (on iPhone this is POSIX)

3. GUI - which can’t be ported automatically to other platforms

Solutions

• For problem with code we can use some emulators of objective-c code - qobjc runtime, cocotron library.

• For system api we can writes wrappers than will be defined on concrete platform.

• GUI - for better case need redesign, for second case you can write some automatic engine for your dialogs.

Open Source libraries

• For code porting (objc) currently we don’t have optimal solutions. Almost all libraries designed for Windows <-> Mac OS but not for iPhone.

But we can use its for:

1. Learning and looking to its implementations

2. Improve this libraries for iPhone

Solutions for code porting

Lib name License Compiler

Cocotron MIT GCC

GNUStep GPL GCC

qobjc Author’s, GPL Visual Studio

qobjc (quick)

Scientific project, this is worked, tested runtime of Objective-C language

Problem: this is only runtime lib, but for full functionality need code parser

http://code.google.com/p/qobjc

Q_BEGIN_CLASS(MyDecl, BaseClass)        Q_INCLUDE_PROTOCOL_TO_CLASS(QMyProto2)        Q_BEGIN_IVAR_LIST            Q_DEF_IVAR(_someInt, i)            Q_DEF_IVAR(_someDouble, d)            Q_DEF_IVAR(_someFloat, f)        Q_END        Q_BEGIN_INSTANCE_METHOD_LIST            Q_DEF_METHOD(calculateArea:, _calcAreaXY, +f+f+f+d+f+f)            Q_DEF_METHOD(dealloc, _dealloc1, +v)        Q_END_INSTANCE_METHOD_LIST    Q_END_CLASS

@interface MyDecl : BaseClass <QMyProto2> { int _someInt; double _someDouble; float _someFloat;}

- (float)calculateArea:(float)v0 :(float)v1 :(double)v2 :(float)v3 :(float)v4;- (void)dealloc; // in objective-c this method not need declare on header :)

Objective-C

Macro code on qobjc

New Code

What benefits?

We can write code on already portable language as - C++, and some scripting

languages - LUA, PostScript

For implementing system API uses libraries (mostly C++) which wraps this

work - example dCocoa, QT

- ?Objective-C

(speciality 2.0) is not cross-platform

dCocoa

Author’s library for cross-platform implementation business logics for iPhone and with possibility run or develop this logic on Windows platform.

http://code.google.com/p/dcocoa

LGPL license

What give your dCocoa now?

1. Convenient Objective-C mechanisms emulation. This library writes on C++ and approximates to Foundation framework with almost all objc-runtime features.

2. Cross-platform between iPhone <-> Windows

1. Keep meta-information

2. Memory management (retain count, autorelease pools)

3. Containers (array, set, dictionary) in 2 form - for standard C++ types and dcocoa types

4. System dependent features (threads, TLS, timer, run-loop, etc)

5. Other helper classes (such as invocation, etc)

Objective-C

@interface MyClass : NSObject {}+ (void)method1;- (void)method2;

void func() { NSAutoreleasePool* pool = [[NSAutorelease alloc] init];

id obj = [[MyClass alloc] initWith:5];

[_someObject addTarget:obj selector:@selector(method2)];

[obj release];[pool release];}

dCocoa

class MyClass : public CL::dObject {COCOA_CLASS_DECLARE(MyClass)typedef CL::dObject _super;public: virtual MyClass* initWith(t a); void method1(); // or virtual

METHOD_DECLARE(method2) // meta};void func() { _LocalPool

CL::dObject* obj = MyClass::alloc()->initWith(5); _someObject->addTargetSelector( obj, dselector(method2));

CoRelease(obj);}

A&Q

Written by Taras Tovcheko, 2009/07/18e-mail: doctorset@gmail.com