Hello
I have used a gradle build script to build a .a static library file from a .m file - written in Objective-C. Now I would like to check if it's working by using the content of the library. When using #import "myLibraryName.a" I don't get access to any of it's contents. How can I use the content of the .a file in a .m file in a SingleViewProject of Xcode, Objective-C?
When you built your static library, you must have had a "myLibraryName.m" file, and you should also have had a "myLibraryName.h" file that the .m file #imports. This .h file should contain the @interface sections for the class(es) defined in the .m file, or at least the public API portions of them, along with any other public definitions (e.g. #defines, enums, structs, etc) that clients of your library should use.
If your original source wasn't organized this way, you should do so now. If there are any private declarations, you can still put those directly in the .m file, so they're not exposed to clients.
After you build your library, you should copy the .a file and the public .h file into a new folder, and add the library to your Xcode project from that folder. Also, in the project build settings, set the Header Search Paths and Library Search Paths setting to that same folder. Using a copy in a separate folder protects your project from failing to build if you start developing incompatible changes to the library.
With these settings, you should be able to #import "myLibraryName.h" in your Xcode project source files, and the public API should be available to the code in those files.
Note that, if your library includes any actual Obj-C classes, you typically need to add the "-ObjC" flag to the Other Linker Flags setting of your project. That's because the default linker behavior is to omit code that isn't explicitly referenced, and because of Obj-C's dynamic nature, this may cause some classes to be left out, causing link errors. With this setting, everything in the library is linked, whether (apparently) referenced or not.
The #import pre-processing directive is for source-code only, not object code. The static library is a collection of object files created by the compiler and the static library archiver during the build process (your gradle build script ends up using the compiler and the archiver). You need to to link the library into your executable with the object files created by the Xcode compiler, clang, from the source code files in your "SingleViewProject" (the .m files).
The "Link Binary with Libraries" build phase would be the place to add the library.
The status was already set to "Required" in the build phases tab - "Link Binary with Libraries", which probably happended when I dragged the .a file into the project. Now what, how do I use it in my .m file? The library was built from a .m file containing a void method "logMessage()" - of which used UIApplication ( and imported UIKit)
You usually create a .h file (or many of them) that lists the public interface to the binary things that are in your .a file.
Your client project (the SingleViewProject) specifies where to find the header/headers in a header path setting.
The code that needs to access the symbols linked from the .a imports those headers.
How can those headers be created? I have read in some places that they should have been generated when building the library file. If that is so - then there is no way for me to use the library inside Xcode to see that it is working?
When you built your static library, you must have had a "myLibraryName.m" file, and you should also have had a "myLibraryName.h" file that the .m file #imports. This .h file should contain the @interface sections for the class(es) defined in the .m file, or at least the public API portions of them, along with any other public definitions (e.g. #defines, enums, structs, etc) that clients of your library should use.
If your original source wasn't organized this way, you should do so now. If there are any private declarations, you can still put those directly in the .m file, so they're not exposed to clients.
After you build your library, you should copy the .a file and the public .h file into a new folder, and add the library to your Xcode project from that folder. Also, in the project build settings, set the Header Search Paths and Library Search Paths setting to that same folder. Using a copy in a separate folder protects your project from failing to build if you start developing incompatible changes to the library.
With these settings, you should be able to #import "myLibraryName.h" in your Xcode project source files, and the public API should be available to the code in those files.
Note that, if your library includes any actual Obj-C classes, you typically need to add the "-ObjC" flag to the Other Linker Flags setting of your project. That's because the default linker behavior is to omit code that isn't explicitly referenced, and because of Obj-C's dynamic nature, this may cause some classes to be left out, causing link errors. With this setting, everything in the library is linked, whether (apparently) referenced or not.
I don't think I can test my particular .a file then. The Gradle build script that created it is intented to be used by Java Native Interface, and JNI can work with .a files without headers. In my case I will have to continue of finding ways to troubleshoot the root of my orginal problem in java. Thanks a lot to all the posts.
