I have a dylib file on my macbook, and I want to use it in an iPhone application I create. I try using dlopen as usual:
#include <dlfcn.h>
char* dylibPath = "/Users/benams/lib.dylib";
void* libHandle = dlopen(dylibPath, RTLD_NOW);
libHandle is null and I guess the reason is that the dylib file doesn't exist on my iPhone. How can I solve it and use this dylib when I debug my app?
In general you can open dynamic libraries on iOS, too. But you can't use a dynamic librray for macOS on iOS, because they have different processor architecturs (x86_64 vs. arm?). You have to compile your library for arm32 and arm64 processors. If you want deploy your app (in the app store), you must also code sign they library.
But it is much easier to create and include a static library for iOS, or use use a shared framework. Note: In general dynamic libraries or shared frameworks will only make sense when reused for multiple executables (e. g. app and its extensions).
Related
I have read many articles about static/dynamic library/framework. So my understanding is (let me know if it's inaccurate):
Framework = Library + Bundle
Static = Linking at build time
Dynamic = Linking at run time
In Xcode, we have "Static Library" and "Framework". Which raises a few confusing points:
Why there's no "Dynamic Library" option?
Given that we can already link framework statically, why do we still need a "Static Library"? (isn't StaticFramework = StaticLibrary + Bundle? )
Why there's no "Dynamic Library" option?
Because Dynamic Library is not permitted for iOS apps at beginning.
Given that we can already link framework statically, why do we still need a "Static Library"? (isn't StaticFramework = StaticLibrary + Bundle? )
Because old Xcode only support Static Library.
Static Framework was added later, and they keep the Static Library.
There are many concepts that must be clear
Libraries have two categories based on how they are linked to the executable file
Static library .a, .so. link at compile time. wiki
Dynamic libraries .dylib .dll etc. link at runtime. only apple can use it for iOS for some safe reason, we cannot build this.
ps, a special kind in apple platform
Text Based .dylib stubs — .tbd
Framework
Framework is a package that can contain resources such as dynamic libraries, strings, headers, images, storyboards etc.
vs Libraries, Framework has more features
Framework also has static and dynamic
iOS 8 later, we can use a dynamic framework, why Apple releases this. maybe Extension and App share code
this Dynamic Framework for iOS is named embedded frameworks, because when we build the app copy the framework in app bundle.
so the embedded framework is different from system dynamic Frameworks like UIKit.Framework
Why there's no "Dynamic Library" option?
the embedded library is allowed with the Framework option, but dynamic framework shared in muti app is also not allowed
Given that we can already link framework statically, why do we still need a "Static Library"? (isn't StaticFramework = StaticLibrary + Bundle? )
well, Xcode not only support Objective-c and Swift, but also support C, C++ which may use the static library
Is there a way to create a framework with two executables inside, one for device and one for simulator, instead of making one fat lib?
You should pack your project as fat framework (different from fat library), this way will make sure the app must strip out the simulator part in order to upload to app store, and the stripping script can be easily obtained in some famous framework like Realm's dynamic framework (required iOS 8+ - if your lib is iOS 7, you can try rewrite the script)
There is no such option. We can see this on libxml example of Apple framework, they have one for device and one for simulator.
I have to admit that with the release of iOS 8 I am a bit confused about dynamic and static frameworks in iOS.
I am looking for a way to distribute a library that I created, and I need to support iOS 7 and above. (Note: This will be a proprietary framework. I cannot use cocoa pods, and I also cannot distribute the source). Here is what I already know:
iOS 8 introduced "embedded frameworks" for iOS, but, as I understand, they do not work for iOS 7, only for iOS 8 and above.
I have the option of distributing my library as a static library (.a file) and also distribute the headers. I know that this is a common way of dealing with the situation, but I would like to find something simpler than that (and also to bundle some resources with it, if possible).
I have also found that iOS 7 does not support dynamic .framework libraries (only static) because it doesn't support dynamic linking. But iOS 8 does, as well as static linking.
And here are my questions regarding this information:
I saw that I can create a .framework target, and make it static, by changing the Mach-O type to "static library. Would that be enough in order to support iOS 7 without any problems, and also to distribute my library as a .framework bundle? If so, why is "embedded frameworks" in iOS 8 that big of a deal, as many resources on the internet are suggesting? Am I missing something?
Is it necessary to codesign the .framework just as I do with any other application I make?
What if I need to include other resources (like Core Data or Images) with my .framework file? Will I need to make a separate .bundle file for that?
Before iOS8, Xcode only allowed the option of creating static libraries for iOS. The common problem with that was we had to ship the binary and headers separately.
Later, some developers came with the idea of creating 'static frameworks'. [the .framework is just a folder with symbolic links to the lib and the headers]. One such example is https://github.com/jverkoey/iOS-Framework
This option will work for iOS 7 or 8 or before that. Because they are just static libraries with the convenience of bundling the headers files along.
As for your questions of the resources, we would need to bundle them in '.bundle'.. For shipping them i am not sure if we can enclose them in the .framework folder.. In the past i used to ship my libs as a static framework and bundle...
However the above option will not work for you if you use Swift. Xcode does not support building static libraries that include swift code.
You must go with Dynamic frameworks if there is swift usage. In theory, Dynamic frameworks work in iOS7.. But, i think iTunes Connect will reject if the app is targeting iOS7 and uses Dynamic frameworks :-).
Hope this helps
Static vs Dynamic linking
static or dynamic in name usually points into a Linking[About] type
Frameworks can be static or dynamic[Check static or dynamic]
You can change the format of library that will have an impact on a Linker by changing Framework target -> Build Settings -> Mach-O Type[About] to Static Library or Dynamic Library. By default Xcode has Dynamic Library value.
Depends on this setting different types of binary will be generated
After you successfully configure a consumer[Link vs Embed]
Static Linker ld: at compile time will include all code from the static library into the executable object file.
Dynamic Linker dyld: at load/run time will try to find the embedded framework using #rpath[About] and link it
[Vocabulary]
With Xcode 9 onwards you can create static frameworks for Swift as well. This is possible due to ABI source compatibility. All you need to do is just change the Mach-O type under build settings of the framework target.
This technique is also applicable to Hybrid Frameworks(frameworks with Swift and Objective-C code).
I don't have all the answers but I'll try to address some of your questions here.
You will get a warning for using these frameworks in iOS 7, however that's all it is, a warning. See this answer.
You can include other resources like CoreData however you'll need to create them in code manually. Here's a tutorial showing how to create a core data model.
You have to code sign dynamic libraries for iOS.
You need to make sure your framework supports both simulator and device architectures if you're planning to distribute it.
Swift does not work in static lib. If you have to use dynamic framework, you have to set min iOS to 8.0 because AppStore reject ios 7 with dynamic framework
I am creating an app using Swift Language in Xcode 6.1 Beta. How to create a .so file? Will the Xcode create a .so file automatically? If yes where can I find it?
Darwin, the OS that iOS (and OS X) use, doesn't use ELF shared objects (.so). Instead, it uses Mach-O dynamic libraries (.dylib). Apple recently added support for frameworks, which includes a dynamic library inside of a directory structure, which can include headers and resources that the framework, or an app linking to the framework, might use.
I have an existing iOS app and want to add a large chunk of code that I've been developing as another project just for ease of testing. The new chunk basically deals with saving an image to various sharing services, etc.. Because that sharing code needs a lot of testing and future updating, I was wondering what the best way to incorporate that code chunk into my existing app.
I don't know if it should be a static library, dynamic library or a framework, and honestly, I'm not really sure what the difference is, or how I should go about it and get it set up in Xcode.
All I know is that I need/want to keep a separate testing and updating app for the sharing code and have the main app use it.
First, some general definitions (specific to iOS):
Static library - a unit of code linked at compile time, which does not change.
However, iOS static libraries are not allowed to contain images/assets (only code). You can get around this challenge by using a media bundle though.
A better, more formal definition can be found on Wikipedia here.
Dynamic library - a unit of code and/or assets linked at runtime that may change.
However, only Apple is allowed to create dynamic libraries for iOS . You're not allowed to create these, as this will get your app rejected. (See this other SO post for confirmation and reasoning on such).
Software Framework - a compiled set of code that accomplishes a task... hence, you can actually have a static framework or a dynamic framework, which are typically just the compiled versions of the above.
See the Wiki on Software Framework for more details.
Hence on iOS, your only option is basically to use a static library or static framework (the main difference being that a static framework is distributed as a compiled .a file most often, whereas a static library may simply be included as a subproject - you can see all of the code - which is compiled first and its resulting .a file used as a dependency by the project).
Now that we're clear(er) on these terms, setting up a static library and supporting media bundle for iOS isn't too difficult, and there are many tutorials on how to do such. I personally would recommend this one:
https://github.com/jverkoey/iOS-Framework
This is a pretty straight-forward guide and doesn't have the disadvantage of dealing with "fake static libraries"... check it out for more info...
Once you've created your static library, it's as easy as including it as a submodule within Git for use across different projects.
Good Luck.
EDIT
Regarding a subproject within a project, as far as I know, to get this to work/compile correctly, you essentially have to set up a compile chain where the subproject is compiled first, which creates a static framework .a file that is used as a dependency by the project.
Here's another useful tutorial which talks about this:
http://www.cocoanetics.com/2011/12/sub-projects-in-xcode/
EDIT 2
As of iOS 8, Apple now permits developers to create dynamic frameworks! (Note: your app must have a minimum target of iOS 8 to include a dynamic framework... back porting isn't allowed.)
This has been added as a new project template. In Xcode 6.1, this can be found at:
New Project -> iOS -> Framework & Library -> Cocoa Touch Framework
Mach-O file format(Mach Object - .o)
In iOS world every source file is converted into object files - ABI[About] Mach-O file[About] which will be packaged into a final executable bundle(application, framework), file (library) and it's behavior is determined by Mach-O type[About]
Package is a directory which behavious itself as a file - opaque file. It is created for user experience to complicate making some changes into internal structure that can cause unpredictable program behaviour. Package is used in Document Package or with a Bundle. You can use Show Package Contents in a Finder
Bundle is a directory with a specific structure to organize a binary(executable code) and resources for that code(e.g. images, nibs... Assets.car file[About]).
Bundle contains Info.plist[About] file. Bundle was created for developer experience. Also it can be packaged. There are several types of bundle:
application bundle - Application target
framework bundle and versioned bundle as a subtype - Framework Target
loadable bundle(aka plug-in bundle) - '... Bundle' (UI Testing Bundle, Unit Testing Bundle) - can be loaded at runtime. .bundle extension for Mac OS
[Mac OS] XPC Service - Cross Process Communication is a kind of Inter Process Communication (IPC). It can be used as a module on a different process(managed by launchd root process)[About]
others(dSYM[About] bundle)
Application - .ipa, .app[About] - packaged application bundle - launchable program.
Application extension[About] - from iOS v8 - extends functionality of Application which are available when user interacts with other application. App extension as a bundle is a part of Containing app but it is run on their own sandbox(processor, memory...), app which try to use app extension is called Host App. Types of extension app:
Action
Share
Photo Editing
Today aka widget
...
to share common code and resources. It's available when Deployment target is iOS 8+.
Tests - packaged loadable bundle which is used to test a binary. Plug-in architecture allows us to add a new functionality(test cases) as a separate module into existing binary
Libraries and Frameworks
[Library vs Framework]
Martin Fowler on InversionOfControl
A Library is essentially a set of functions that you can call, these days usually organized into classes. Each call does some work and returns control to the client.
A Framework embodies some abstract design, with more behavior built in. In order to use it you need to insert your behavior into various places in the framework either by subclassing or by plugging in your own classes. The framework's code then calls your code at these points. The main control of the program is inverted, moved away from you to the framework. This phenomenon is Inversion of Control (also known as the Hollywood Principle - "Don't call us, we'll call you"
Libraries and Frameworks on iOS
They can help you to solve: modularity, reusing, encapsulation, improve build time
Library is a collection of Mach-O object files[check static or dynamic] compiled for one or more architectures.
Static library - .a(aka static archive library, static linked shared library[doc]) - When you add it into your application the static linker during compilation time will merge the object files from the library and package them along with the application object files into one single executable file. The disadvantage is a big output file
From Xcode 9.0, Swift static library is supported.
Dynamic library - .dylib(aka dynamic shared library, shared object, dynamically linked library[doc]) is dynamically linked with the app's executable at load or runtime, but not copied into it. On practice app's package will contain Frameworks folder with .dylib file. All iOS and macOS system libraries are dynamic. The disadvantage is a slow launch time since all dynamic libraries should be copied and linked.
[iOS static vs dynamic library]
[Static vs dynamic linking]
Text-based stub library - .tbd[About], it is a text stub of dynamic library which is located on a target device. As a result you should not package a dynamic library into your bundle. It has a size effect.
Framework aka binary framework - .framework is a not packaged framework bundle(to allow developers to easily take a look at headers and resources) which contains a compiled static or dynamic library, header files and resources.
Static framework contain a static library packaged with its resources.
Dynamic framework aka Embedded framework - from iOS v8 - contains the dynamic library and resources. In addition to that, dynamic framework can include different versions of the same dynamic library in a single bundle (versioned bundle). Also Embedded framework is used in App Extension
[Static vs dynamic framework]
Umbrella framework [Aggregate target] is a framework that contains other frameworks. It is not officially supported on iOS and that is why it is not recommended for developers to create them[Official doc]. In actuality it's a set of sub-frameworks(or Nested Frameworks). When you create a framework which has a dependency, a consumer (such as an app) is responsible for adding this dependency along with your framework into the project. As a developer, it's natural to try to find a way to transfer this duty from consumer to your's. As a result you think that Umbrella framework is the rescue but usually it leads to a serious issues with managing versions and complexity of creating and supporting it.
Fake Framework - is a result of specific operations under a static library to create a bundle with .framework extension that will behave yourself as a dynamic framework. This technic was used when Xcode did not support creating a framework since did not have a framework template. One of realisation of a fake framework. With Xcode 6, Apple has added iOS framework support.
Modular Framework[About] - #import it is a framework which contains a .modulemap file inside. Module can contains submodules. The main advantage is that you save a build time with Modular Framework.
Universal Library or Framework (aka Fat) [lipo] [Aggregate target] contains multiple architectures. For example your release build should support a some arch which you can regulate via Build Active Architecture Only [ONLY_ACTIVE_ARCH]
XCFramework[About] was introduced by Xcode 11 and it is a bundle which includes multiple architectures(arm, x86_64...) and platforms(iOS, MacOS...). It should replace a Universal Framework
Dependency[About] You are able to use third party code as a part of your target. It allows you to reuse a code from a lot of sources like - another project, project in the same workspace, another target, library, framework etc.
How to build and use a Static Library:
[Swift consumer -> Swift static library]
[Swift consumer -> Objective-C static library]
[Objective-C consumer -> Swift static library]
[Objective-C consumer -> Objective-C static library]
How to build and use a Dynamic Framework[change to static]
[Swift consumer -> Swift dynamic framework]
[Swift consumer -> Objective-C dynamic framework]
[Objective-C consumer -> Swift dynamic framework]
[Objective-C consumer -> Objective-C dynamic framework]
[Xcode Build System]
[Xcode components]
[Dynamic linker]
You can also create .podspec file for CocoaPods( http://guides.cocoapods.org/making/private-cocoapods.html#1.-create-a-private-spec-repo ) and use it like any other pod with the only difference that it's your private pod and is not visible to outside world(I'm not sure what will happen if your pod should create CoreData model, but that's not the case, as I understand).