Great post Walter, thank you for taking the time to explain this!
Jeff
On Tue, Oct 11, 2011 at 6:29 AM, Walter Szewelanczyk
<walterszewelanc...@gmail.com> wrote:
> As a new to MonoTouch user myself, I had some issues with this as well.
> Primarily in what btouch actually did and how to setup to use it. At
> first I thought btouch would take the library itself (the .a file) and use
> that automatically produce the .Net dll, then I was thinking it would take
> the .h file and do it, but really thats not the case at all.
> Really what happens is that you need to build a .cs file that has interfaces
> that use annotations that tell btouch how to build the real classes that do
> the mapping to the Obj-C lib. Now if you have done some basic p/Invoke you
> may be thinking that if you have already annotated a .cs file why do you
> need btouch at all. You technically dont, but btouch does save you a lot of
> effort as there is a lot more work than with a typical c style interop.
> The other thing to note is that the interface file will never actually
> be referenced by your code base once you generate the dll in btouch. It is
> used only so that btouch knows what you need built, and you get real classes
> and your interfaces are not actually referenced.
> So to get some experience with this I built a simple Obj-C lib with the
> following header :
> --------------- BEGIN ObjC HEADER --------------------
>
> #import <Foundation/Foundation.h>
> typedef unsigned char UCHAR;
> typedef struct
> {
> UCHAR messageSize;
> UCHAR messageId;
> UCHAR data1;
> UCHAR data2;
> } Stuff;
> @protocol StructDelegate
> - (void)processStruct:(Stuff)antMessage;
> @end
> @protocol SimpleDelegate
> - (NSString*)process:(NSString*)msg;
> @end
> @interface TestLib : NSObject
> {
> id <StructDelegate> del;
> id<SimpleDelegate> sDel;
> }
> - (NSString *) RepeatAfterMe:(NSString*) repeatMe;
> - (NSString*) SayHello;
> - (int) HardCodedValue;
> - (NSString*) Send:(Stuff) s;
> + (NSString*) classMethod;
> - (void) save:(id <StructDelegate>) d;
> - (void) saveSimple:(id <SimpleDelegate>) d;
> - (NSString*) callSimple:(NSString*) s;
> @end
> --------------- END ObjC HEADER --------------------
>
> So you will notice we have a C style struct, some protocols and an Objective
> C style class with static and instance methods.
> Now I wanted to be able to use this in MonoTouch so here is the Interface
> file I built for bTouch :
>
> ------ BEGIN btouch Mapping File ----------
> using System;
> using MonoTouch.Foundation;
> using System.Runtime.InteropServices;
> using MonoTouch.ObjCRuntime;
>
> namespace libTestLib
> {
> [BaseType (typeof(NSObject))]
> [Model]
> interface StructDelegate
> {
> [Export ("processStruct:")]
> string processStruct (MyStuff s);
> }
> [BaseType (typeof(NSObject))]
> [Model]
> interface SimpleDelegate
> {
> [Export ("process:")]
> string process (string s);
> }
> [BaseType (typeof (NSObject))]
> interface TestLib {
> [Export ("RepeatAfterMe:")]
> string RepeatAfterMe (string repeatMe);
> [Export ("SayHello")]
> string SayHello { get; }
> [Export ("HardCodedValue")]
> int HardCodedValue { get; }
> [Static, Export ("classMethod")]
> string ClassMethod { get; }
> [Export("saveSimple:")]
> void SaveSimple(SimpleDelegate del);
> [Export("callSimple:")]
> string CallSimple (string s);
> [Export ("save:")]
> void Save(StructDelegate d);
> [Export ("Send:")]
> string Send (MyStuff s);
> }
> }
> ------ END btouch Mapping File ----------
> Now notice the struct is not referenced in this file. Btouch will only
> output classes for the interfaces in the main file so we need to included
> the extra things we need in other files. In this case we need a file to
> define the struct.
>
> ------ BEGIN btouch struct File ----------
> namespace libTestLib
> {
> public struct MyStuff
> {
> public byte messageSize;
> public byte messageId;
> public byte data1;
> public byte data2;
> }
> }
> ------ BEGIN btouch struct File ----------
> to build the .dll run btouch -v theInterface.cs
> anyExtraFilesLikeOurStructFile.cs
> This will produce a .dll that you will include into our MonoTouch project.
> You do not need to include the interface or extra files into the project
> itself as they are already built into the dll. ( I do include them in a sub
> dir with the lib, but I have the build action set to nothing ).
> Once you build the dll I would encourage you to look at the dll in
> MonoDevelop and see how much extra stuff is generated for you by using
> btouch.
> now in your real code you can invoke things as follows :
> var t = new TestLib();
> var s = new MyStuff();
> s.messageSize = 1;
> s.messageId = 2;
> s.data1 = 10;
> s.data2 = 11;
> Console.WriteLine ("This is from objC sayHello : {0}", t.SayHello);
> Console.WriteLine ("This is from objC send : {0}", t.Send (s));
> Console.WriteLine ("This is from objC static : {0}", TestLib.ClassMethod);
>
> Hopefully that helps a bit on how btouch actually works and helps you
> started in the right direction.
>
>
> Walt
>
>
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>
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