I have an app that has many components. In my case, there are several visual assets (a pie chart, a bar chart, a line chart, etc), and I'd like to be able to reuse those across multiple projects.
I have coded everything with a nice, top level delegate, which if implemented, the component can run on its own. (similar to UITableViewDelegate, or the like).
What's my best bet for separating the code out? It seems that the options are to create a Framework, or to use a subproject in XCode.
Frameworks look pretty robust, but seem complex to create. Also, with a framework, can you debug/step through code within the framework (assuming I have all the source, since I wrote it).
If anyone has done this for themselves, I'd be grateful for some insight.
I like to package reusable components into CocoaPods and either put them in a shared spec repo or reference them directly in the project's Podfile.
Related
I have 2 frameworks created by me that use (both of them) a library also created by me.
The first framework initialize the library and makes all its workflow. After finishing the first framework, the second one must start.
But when the second one is going to start, after initializing the library, the app using both frameworks crashes with a exc_bad_access error.
Apparently the library is created correctly, but if i comment the line of code to initialize the library in the second framework, the workflow continues (it crashes later because it has no library initialization).
Is there anything I'm doing wrong? Should I use two separate libraries instead?
EDIT:
Imagine the situation:
Framework A has this methods: start, stop. And while it works it delegate to the methods: infoFromA,frameworkAFinished.
Framework B has this methods: start, stop. And while it works it delegate to the methods: infoFromB,frameworkBFinished.
Both start methods initialize the static library mentioned (lets call it problematicLibrary).
Both frameworks present some views to make its functionality. So lets make an example of the app workflow.
At the app view viewWillAppear method, I start the Framework A just using:
[FrameworkA start]; , this will initialize the library and present a view. With this view (using my problematicLibrary) some info will be delegated to the infoFromA delegated method. And after all the info is delegated, it will delegate to frameworkAFinished.
When the FrameworkA has delegated to the frameworkAFinished I start the next Framework: [FrameworkB start]. As the other Framework, it will initialize the library and present a view. While debugging, all the initialization of the library is done (create the instances of the needed objects and a new instance of the library is created) and while its presenting the view it goes through the viewDidLoad method and then it throws an exc_bad_access error at the problematicLibrary initialization line (which has been done before and continued to present the view!!) without going into any other method from the view.
I have checked if the initialization is doing well, and all the variables were at null value before the initialization, and a new memory address is given to the library object.
This sounds strongly like a symbol conflict to me. I'm just surprised the linker didn't catch it, but I assume that's because you're using a static library in both your frameworks instead of simply yet another framework.
Generally speaking, I'd warn that "this is a bad idea™". What you're trying to introduce into your design is basically dependency management. Like a lot of blog articles and specifically this SO answer suggest, you should avoid packaging frameworks (and by extension libraries) into frameworks.
What most likely happens in your scenario is this (I admit I'm guessing a bit here): You linked the library into Framework A. Thus, the library becomes a fixed part of it. Its symbols are in it, even if you did not expose them to the app in any header files or the like. As long as you use only that, everything works smoothly. Then comes Framework B, of which the library is also a fixed part. Even though you can't see it from your app, the very same symbols are inside it. This, however, clashes with the symbols that were already loaded by Framework A, hence a crash (as said, this would usually be caught by the linker, but I guess you "tricked" it by building the frameworks beforehand and packaged the library in them). Maybe somebody else can explain this in more detail, but that quickly becomes besides the point as to how you would go for a solution. From how I see it, it just won't work this way.
So here's a suggestion for how you can solve your problem:
If you really, really need to split like this (two frameworks used in your app using the same dependency), I'd suggest removing the library from the frameworks (i.e. make them depend on it, but not package the actual .a file in them) and documenting that properly. Then add the library to your app project, just like you added the frameworks.
If you want to make this fancy and easily installable into other apps, I'd recommend setting up a private CocoaPods repository and turn your frameworks into private pods. You can then easily define the library (or rather "new Framework C") as a dependency for Framework A and Framework B. When you then pod install in your app, cocoapods figures out the dependency and adds Framework C automatically to your project. This scenario is exactly what cocoapods (or any dependency manager for that matter) was designed for. It automates and helps in the project setup, so that the final build (the app) doesn't have to figure out dynamically what it can and can't use. The end result is the same.
Trying to duplicate that "in code" quickly becomes messy. Frameworks trying to figure out things of the surrounding app/project that uses them (like "is my dependency so-and-so already linked? if not, can I load my own version of the library?") can lead to a lot of pain.
Okay, in response to your comment I'll try my hand at a more detailed How-To for the non-cocoapods setup. As a preface, though, let me say that that's kinda hard to do on top of my head, as I have no ready sample project to toy around with. Since this is one of those "set it up once and then forget aout it for a long time" I have to admit my recollection of these things is a bit fuzzy, so consider this as a sort of "rough direction". There might be things you need to configure differently than how I recall them. Other SO user are thus hereby invited to edit and correct my answer here, too. :)
First, I have to say I am not exactly sure whether you need to convert your static library into a framework or not for this, I think you don't so I'll go from here (I have never used a static library in that way).
That means you can leave the project that builds your library as is. On second thought, you probably have to do this to be able to link against the library without making it a part of the framework that uses it. I will still refer to this code as "library" in the below points, but assume that you're able to turn it into a dynamic framework as well.
The projects building Framework A and Framework B should be changed. I don't know how you have this set up (as one project with various targets, whether you have a "development application" as part of it to test the frameworks on themselves, etc.), but the important thing is that in the target that builds a framework, the library should be linked (i.e. in the "Link Binary With Libraries" build phase), but not copied (i.e. it must not be in the "Copy Bundle Ressources" build phase). It might be tricky to set up any development/test target you use to run, depending on how you did that so far. For example you might have to manually edit Library Search paths in your build settings to be able to properly compile the framework.
Lastly, you need to change your final app's project settings, obviously. The library that was originally part of Framework A and B now needs to be linked to from its project directly, and, obviously, it needs to be copied into the bundle as well. Note that any projects that include either of your frameworks (A or B or both) in the future must do so, otherwise they won't work, because these frameworks expect the library to be present (but no longer "bring it with them").
In spite of this long-ish text wall, it shouldn't be that complicated, I think, but you may still want to check out how cocoapods can support you with something like this, perhaps it's helpful in the future. The linked article expects basic knowledge on how to use a pod and write one, but the other guides on the site explain that pretty well. I am just saying this because in the end, when using cocoapods in a project to add multiple libraries/frameworks that introduce dependencies, it basically sets up your project in the way I described above. It uses some fancy shell scripts that ensure everything is copied to the correct folders and such, but overall speaking that's how it works: A pod's podspec tells cocoapods what additional pods to include in your app for it to work (a dependecy the pod expects to be there, but doesn't "bring in" by itself).
Check if they are both compiling for the same target.
Check if they have access to the same target membership.
Check build phases to see that they are both there.
I think because the first library is not 'well' referencing the second one.
Also i think that you can't import a framework inside another one.
To make things easier, you can merge the two frameworks on a single one.
Also you can add a callback (using protocols or closures) that informs for the end of the first workflow, and you use this callback to initialize the second framework. This way the initialization will not be made automatically.
I am a (very) novice iOS/Swift programmer with a basic question about moving reusable software objects to their own ... something.
I am developing three iPhone apps that present information from three distinct data sets. Those data sets contain unique information but are structurally similar. As such, the apps share some Swift classes that are identical, specifically the classes that model the data. As I continually refactor the code, I find that when I tweak a class in one app's project, I have to remember to go to the other two projects and make the same tweaks to the same classes for those apps. It's getting to be a big headache.
What I would like to do is have one class definition in its own ... something that I can share, link, import, or attach to/from each app's project. From my online research, I suspect that the ... something is a library? or maybe it's a framework? or a module? I have found all three terms are used, but I am not sure how they relate to each other.
Given that all of the software I am writing is in Swift, does Xcode support what I am trying to do? Thank you!
It seems you have the issue of needing the same Swift class in multiple projects. You could build a Framework (aka Module) for this class then copy it in to each project. This is probably the formally correct approach but it is a bit of overkill for just a single class.
Instead, you could just make the file in the Navigator panel a reference in each project to the one actual file.
You could also make a Workspace and then put each project into the workspace and just have the file at the top level (but this may introduce some build complexity).
I built an iOS project (actually workspace because of Pods) that is 100% functional, with its logic and UI (Storyboard and xibs). Now I would like to reuse this app/project as a "core" for future apps.
I've been searching about it and there are several solutions like Static libraries, Frameworks and Targets. But I am not sure which one would be the best in my case. I would like to reuse all the UI part as well.
I saw that most of the people agree that the best approach for reusing code is static libraries, even thought it looks not so straight forward. But I think for reusing UI probably Targets is the best solution. The problem I see is that if a build 10 apps based on my core project, the new project will be huge, so probably it is not the best option.
I don't know if you guys have any better idea or opinion.
Thanks in advance!!
There are several things you can do, and I will try to go through them.
If you have minor changes on your "base" app, then the best thing would be using targets(build schemes). This way you can add things to build phases and therefore, add files that you need. This might be the quickest possible way to do what you want but here are some drawbacks: What if you have 5 apps, and for each one you have QA and prod. That 10 build phases. If you keep using your app in no time you will find hard to manage it.
Another thing could be to create different project, and include all the files you have (and you need), inherit from there and have extended functionality/UI/UX. This is slower approach then number 1, but you will have dependency on the files that you might change in one app and don't want to propagate that change in other apps. So the drawback would be that you have to be extra careful, and plan a lot of things in advance.
Third thing could be to create base app group(or project) and then you are certain what to do, where and what that change could do to other apps(since you know that this file is actually being reused).
And finally, there is a framework, which is my favorite. I am working on one project that inherits base app and we found that is a huge problem. You start separated and then, one thing by one, you have entangled code for specific app and base app like headphones in pocket. And if you don't refactor it ASAP, it will became really hard to resolve these kind of issue. Not to mention merging and other stuff. Here is an excellent article about creating framework http://www.raywenderlich.com/65964/create-a-framework-for-ios . Off course, there is a price to pay and that's every change that you create you must update library and add it again to project. This thing can be easily forgotten and if you are working in team could produce build crash.
All after all, you predicate that you will have more then 5 apps, so I would say go with the framework. This way you will have much cleaner and separated app, and won't have to think about changing things and how these changes would affect your other apps.
I recommend you use a custom project template. I did it perfectly today. I had the same needs as your. Follow this link: https://github.com/reidmain/Xcode-6-Project-Templates/tree/master/iOS%20Application.xctemplate
Download it. You can add all the files from existing project into this template, storyboards too. If you have any doubts I will help you.
Using iOS 8, Xcode 6.
Let's say I have 2 dynamic frameworks, frameworkA and frameworkB and they are both dependent on libC. In addition, I have an app that uses both frameworkA and frameworkB. My original thought was to make frameworkA and frameworkB umbrella frameworks and libC a subframework. However, Apple advises against umbrella framework and this post describes why umbrella framework is a bad idea due to potential linker conflict issue.
My second option is to use cocoapods (still new to this so a bit fuzzy on details) to use libC as a pod which then gets compiled into frameworkA and frameworkB. However, it occurred to me that both frameworks still has its own copy of the libC. Since the app uses both frameworks, will this result in a linker conflict issue as well? Is there a better way to solve this problem?
UPDATE
#Rob The projects I work on do require complex dependency management but I kept the problem domain simple in the question to try to better understand how and if using cocoapods can help solve the linker conflict issue with umbrella frameworks. I work with a team of developers who write libraries and can depend on each other's base libraries that provide versioned common APIs. We are required to package and deliver as few libraries as possible to a different organization that is building an app with our libraries and one of their key requirement is that we deliver a dynamic framework.
The best way to solve most problems is to put all the code in a project and compile it. When you have specialized problems that make that problematic, then you should look at other solutions, such as static libraries, and finally frameworks.
Static libraries can make sense if you have a code base that has pieces which require different build requirements. If all the pieces have the same build settings, then just "add files" them into your project from a "common" directory and build your project. Static libraries can be attractive if your build times are very significant and some pieces never change and you want to be able to "clean" without rebuilding those parts. But wait until you start having that problem before you go making complicated multi-package projects.
If you sell closed-source libraries, then frameworks are very attractive. You should strongly avoid adding third-party dependencies for the reasons you note. If you must, the best way is to help your customers package all the pieces as frameworks and have them link everything at the end. But that adds a lot of annoyance; so make sure you really need that third-party piece.
You might also consider frameworks if you have a very large piece of reusable code that has its own lifecycle separate from the main products. But again, keep it simple. Avoid third party stuff inside of it, and if you must have third party stuff, then have the consumers link it at the end.
(This isn't a new solution, BTW. When you use curl, if you want SSL, you need to also download and build OpenSSL and link them together yourself. Curl doesn't come with OpenSSL built in.)
But in the vast majority of cases, this is all overkill. Don't jump to frameworks. Don't jump to libraries. Just put all the code in the project and compile it. 90% of your problems will evaporate. iOS projects in particular just aren't that big usually. What problem is a framework solving?
If you have a lot of code that your organization uses repeatedly in lots of products, then I have heard many teams have good luck using internal CocoaPods to manage that. But that's just to simplify checking the code out. It still all goes into a project and you compile it together into one binary; no frameworks needed. Dynamic frameworks are a nice feature in for certain kinds of problems that were really painful before. But, for most situations, they're just complexity looking for a problem.
(If you have one of those specialized problems, edit your question and I'm happy to discuss further how you might approach it.)
EDIT: (You fall into that "specialized problem," so let's talk about it. I did, too, for many years inside of a large multi-team Mac and iOS dev environment. And we tried just about every different solution, including Frameworks. They're only new on iOS.)
Within an org like you describe, I would strongly recommend packaging each dependency as its own framework (AFNetworking, JSONKit, etc) and each of your pieces as a framework, and then have the app devs link all of them together at the end. In this way, it is identical to other dynamic libraries (libcurl, openssl, etc.) which require the app dev to link everything together.
In no case should dynamic frameworks include other frameworks that could otherwise be required (i.e. frameworks should never package "third party" stuff). That will explode. You cannot make that not explode. You'll either have bloat, build conflicts, or runtime conflicts. It's like merge conflicts. There's a point at which a developer has to make a choice. App-level linking is making that choice.
Making components over-dependent on other components is the source of decades of trouble, from Windows DLL Hell to iOS apps with competing crash handlers. All the best component systems look like Legos, where the end user assembles small pieces that have minimal dependencies. As much as possible, make your internal frameworks rely on nothing but Cocoa. This has some tangible design influences:
Avoid directly requiring logging or analytic engines. Provide a delegate interface that can be adapted to the engines of the caller.
Avoid trivial categories (methods that save just a few lines of code). Just write the code directly.
Avoid adding framework dependencies that aren't buying you a lot. Don't add AFNetworking just to save a few lines of code over NSURLConnection. Of course if you're heavily relying on the features of another framework, that's different. But as a framework developer your threshold should be quite high before requiring another framework.
Strongly avoid being clever in the build or version control. I've seen too many cases where people want to make everything "automatic" for the app-level developer, and so make the system really complicated. Just say "you need to link this and import this and put this in your app delegate startup." Don't create complicated build and version control systems to save 2 minutes on the first build or two lines of initialization logic. These things blow up and waste hours to work around. Don't get clever with +load magic. Just make it clear and consistent.
And of course, good luck. Supporting other devs is always an interesting challenge.
In a brainstorming meeting, someone recommended that we use a static library in a future project. I have researched this topic all day.
I have found some helpful answers about what a static library is and how to create one.
Library? Static? Dynamic? Or Framework? Project inside another project
I've also found answers on how to use resources with a library:
iOS Library With Resources
My Question Is:
Do I really need to create a static library, or should I just create a class for internal-use-only code?
Conditions:
I have three projects that require a special encode and decode engine.
The engine's functions involve cryptography, IP packet transport, and hardware binary coding.
There are fewer than 20 functions.
We will never release this engine to a third party developer or open source it.
Another way to ask:
In what circumstances should I create a static library?
Even if you don't want to share your code with other developers, you can still gain tremendous benefits from creating a static library.
As Srikar Appal mentions, benefits gained from creating a static library are 1) Code Distribution, 2) Code Reuse, and I'd also like to add, 3) Versioning, 4) Testability (kudos to BergQuester's comments below) and 5) Documentation.
Let's look at these more closely:
1) Code Distribution
Static libraries are great because they make it easy to distribute your code- all you have to do is compile and share the resulting .a file.
Even if you never plan to share your code with other developers, you can still make use of this across your own projects.
Alternatively, you might instead include the static library's project as a subproject to your various main projects, making this a dependency of the main project... see https://github.com/jverkoey/iOS-Framework for how this can be setup.
2) Code Reuse
Even in very different apps, you'll often find that you're doing the same task that you'd previously written code for. If you're an efficient developer, you wouldn't want to write the same code again... instead, you'd want to just include your previously written, polished code.
You might say, But I can just include the classes directly.
What if your code isn't necessarily polished, however? Or as tends to happen, the frameworks it uses change over time?
As you make changes and bug fixes to the code set, it'd be nice to be able to easily include the latest version in your projects (or be able to easily update your projects later on). A static library makes this easier to do because all the related code is included within a single package.
There's also no worrying about what other project-specific hacks other developers have been imposed on it - the main project can't (or in the case of a static library included as a subproject, shouldn't) change the static library's code set.
This has the added benefit that if someone does need to change the static library's code set, he must make the change such that all projects relying on it will still be able to use it (no project-specific shortcut hacks).
3) Versioning
If you have a set of classes that are moved around and included project to project, it's hard to keep up with versioning. Most likely, the only versioning you do have is that of the main project.
What if one project fixes some bugs and another project fixes other bugs within this class set? You might not know to merge these changes (what if two teams are working separately even on these)? Or, each project might be fixing the same bugs!
By creating a static library, you can keep track of versioning (the static library's project has its own version number), and by making changes on the static library, you'll have less merge issues and eliminate the risk of fixing the same bugs over and over.
4) Testability
As iOS continues to mature as a platform, unit testing your code is becoming more and more prevalent. Apple even continues to build and expand on testing frameworks (XCTest) to make it easier and faster for iOS developers to write unit tests.
While you could (and, IMHO, should) write unit tests for your code at the application level, creating and encapsulating code withIN static libraries typically makes these tests better and easier to maintain.
The tests are better because well-designed static libraries encapsulate purposeful functionality (i.e. a well-designed library performs a specific task, such as networking tasks for example), which makes it easier to "unit" test the code.
That is, a well-designed static library sets out to accomplish a predefined "purpose", so essentially, it creates test boundaries naturally (i.e. networking and presenting the fetched data would likely be at least two separate libraries).
The tests are easier to maintain because they would be within the same repository (e.g. Git repo) as the static library code (and thereby, versioned and updated alongside this code). Just like you don't really want to copy and paste code from project to project, you similarly don't want to copy and paste tests, either.
5) Documentation
Like unit testing, in-line documentation continues to become more important in iOS.
While you can (and again, IMHO, should) document code at the application level, it's again better and easier to maintain if it's at the static library level (for the same reasoning as unit testing above).
So to answer your question,
Do I really need to create a static library, or should I just create a class for internal-use-only code?
You might ask yourself the following:
Will this code be used across multiple apps?
Will this code ever have more than one class?
Will multiple developers be working on or using this code concurrently (possibly in different apps)?
Will this code be unit tested?
Will this code be documented?
If you answer YES to most of the above, you should probably create a static library for this code. It will likely save you trouble in the long run.
If you answer NO to most of the above, you might not gain much benefit from creating a static library (as the code set would have to be very specific to a project in such an instance).
In my opinion creating a static library has the following benefits -
Code distribution - This is the biggest reason (perhaps the only reason) developers create a static library. It obfuscates the actual code and exposes the API methods. But since you have explicitly mentioned that this "library package" would never be distributed to 3rd party developers this reason might not apply.
Code Reuse - This is the other reason I can think of. But then, one can achieve code reuse by simply using classes in (.m files), having the method definitions in header file & importing the header file (.h files). So this is not much of a reason to create a static library.
I am not aware of any performance benefits due to statically linked code. Also creating static library has its own maintenance overhead. It would not be as simple as creating one build. You would have to keep in mind linking the static library, maintaining compatibility etc.
So in your case creating a static library might not make much sense.