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I have been developing iOS apps for about a year. In that time, I have developed a fair number of classes that I frequently recycle from app to app. For example, I have a bunch of classes related to making it easier to write table views to control in-app settings.
Right now, I simply grab these classes from one app and paste them into the next one. My question is -- at what point is it likely to be easier to create and use a static library?
Static libraries have their problems as well.
Using a static library discourages you from fixing problems as you see them, since the code is in another project and it becomes troublesome.
GCC has a bug in whereas any method defined in a category is optimized away from the static library. Not good if you library code consist of lots and lots of convenience categories on existing classes.
So what you want is a solution where you can add dependencies to actual source code. This way you avoid the nasty GCC bug, and the boy scout rule is encouraged!
Our solution is a simple dependency system based on Rake. It creates sym-links to the source code of the shared libraries, and hard copies when building on the build server (You should never build the distribution binaries on a developers own machine!).
The sym-links allow developers to edit the shared code just as if it was part of the current project, while ensuring any cleanups, bug-fixes, etc. are always propagated to a single repository and benefits all projects using the shared library.
The hard-copies on the build server allows for the shared libraries to be tagged for version, so that the exact build of v1.0 you sent to App Store is forever reproducible!
A colegue of mine have blogged about setting up a build server for continious integration here: http://blog.jayway.com/2010/01/31/continuos-integration-for-xcode-projects/
I will nag him to blog and share the Rake based dependency system as well. It is basically just a handful of lines with Ruby script.
I have my own library of miscellaneous stuff.
I add things to it that I deem to be reasonably generic and that I can envisage using in the future at some point.
After all, there's no harm in adding it to your library, even if you never use it again.
As soon as you tire of copying and pasting you should create a library. Or, as soon as you make your first mistake (mis-)copying and (mis-)pasting.
Or, in more business-like terms: when the net present value exceeds the net present cost.
If you want to distribute your classes out to your "team", then you will not have to worry about changes they make to your code, thus keeping the libary consistant.
Or if you wanted to sell your classes as API's to another DEV team then your can hide the source code from the API user.
I have a few "utility" classes that I find usuful and I do tend to drop the class file into my solution as I find it easier and quicker, (not that the extra 2 to 3 clicks matter), so really i suppose i do it out of habbit more than anything else.
Another solution is to use use a version control system (such as git) that supports submodules. You can wrap up each of these helper classes (or even a collection of classes) in its own repository which can be imported into the main repository of your code.
In this way you don't have to worry about cutting and pasting errors. Also, if you make improvements to these classes they can be propagated to other projects that use them (if you want to), yet you can always roll back to previous versions for bug fixing / testing.
It is common to find such helper code on sites such as github example
I have a static library that is in a separate project.
That way I can fully develop the library, complete with unit tests etc. and then simply re-use it by making another project dependant on it.
It means I don't have to cut/paste, and it also means that should I find/fix a bug, or add/modify a feature of the library, then it can be regression tested easily.
Now all the projects that use that library can benefit.
So for my money, the time to turn a collection of 'useful code' into a library is certainly when you find you want to use it again.
(Of course we all have useful code snippets we re-use by copy/paste from a previous project - those aren't necessarily right for being in a library.)
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I have a paid application on the android marketplace, however, I want to release a free ad-supported version.
The easiest way I thought to do this was to set up a branch on my subversion repository that has the additional code to add the ads. However, when I went to submit this to the android marketplace, they require unique package names. This solution no longer works for me because I'd have to change the package of every class file, which would make merging the trunk and branch very painful.
What is the best way I can keep these two projects together, sharing patches, but with a different package?
Have you considered compiler directives?
Example:
#define FREE
// ...
#if FREE
Console.WriteLine("Free version");
#else
Console.WriteLine("Paid version");
#endif
You can keep the exact same code base and target the two builds using two separate build scripts or a parametrable one.
msbuild /p:DefineConstants=FREE
To do it with Java, read this and this. And maybe this.
Only your application package must be unique. See here. That's the package declared in your manifest file. You can have most of your code in com.mydomain.myapp, and just have a different main activity in com.mydomain.myapp.free.
If you really want to do separate, the best way is to set it up as two parts of the same repository. That way you can at least merge changes across the different branches. If you want to keep things completely separate then you will be doing alot of schlepping patch files.
I've done this and frankly it isn't a great strategy in practice. Much better, especially in compiled environments, is to have a separate build process for free versus paid so there is one codebase rather than two. If there are two codebases things will diverge.
Version control is a poor way of managing things like this. You'll end up with a maintenance nightmare - two separate applications that need to be almost identical.
Have you considered a multiple project solution? (caveot: I haven't actually done this, but it seems feasible, and I think Android will allow it. I'll try it later and see for sure.) Compile all your app code into a main project jar. Then create two separate Android apps, one for your paid version, and one for the free version. This will solve your package naming problem. These apps will just delegate to the main jar for pretty much everything, except that your ad version will include the code to support the ads.
You may also find this discussion on a similar topic interesting.
Building your app using a feature toggle would allow you to reach your objective but you might have to rework a lot of code.
By defining 2 (I would recommand 3) feature container environment in a .ini file like :
[paid]
features.ads = false
features.featureOne = true
features.featureTwo = true
features.premiumFeature = true
features.underDevFeature = false
features.debug = false;
[free:paid]
features.ads = true
features.premiumFeature = false
; And the optionnal third
[development:paid]
features.debug = true
features.underDevFeature = true
This way, you have a version that that is uniform and require only one branch in your version control source
In your specific scripts you then have to check if the feature is authorized, if not, you dont display it
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Wether you call it Addons, Plugins or extra peices of code that is connected with the original software later, it really doesn't matter. I would love to understand how they work, there has to be a simple explanation of how to design a Plugin System. Unfortunately, I never understood it, and there remains a lot of open question in my mind. For example, how does the program find a plugin? how does it interface with it? when is it preferable for a software to have Plugin System?
Thanks for all helpful answers. It seems I asked too open question, fortunately I got keywords to look for. I liked David answer though I am not a Java guy, but his talk made sense to me :)
Plug-ins work by conforming to well-known interfaces that the main application expects to work with.
There are several ways in which a plug-in architecture actually works, but in general, these are the steps:
Plug-ins are designed to match an interface that the application expects. For example, a simple application might require that plug-ins implement a IPlugin interface.
Plug-ins are loaded by the application, usually when the app is starting up
Plug-ins are often provided access to much of the data that the application manages. For example, Firefox plug-ins can access the current web page, and Eclipse plug-ins can access the open files.
Here are two ways (out of several) in which an application can find plug-ins:
The plug-ins are known to exist in a particular folder, and the application knows to load plug-ins from that folder
Each plug-in runs as a service, and the services are designed to work together (this is how an OSGi-based application works)
When plug-ins are found, they are loaded by the application (sometimes the job of a Class Loader).
A software architect might design a plug-in architecture when they expect that either the software provider or the user community will implement new features that were not originally part of the system. Two great examples are Eclipse and Firefox; other applications include Adobe Photoshop (for artistic techniques and graphical tools) and Winamp (for visualizations).
Create an interface that all plugins of a particular type will implement
Write the code that will 'consume' the plugin against the interface only.
Have a dynamic way to load a DLL containing the plugin type that implements your interface (for instance, have a configurable folder location to test whether any DLLs in that folder contain any types that implement your interface, and dynamically load any that do. In .NET this might use Assembly.LoadFile())
If you want to have a look at some source code, Paint.NET is free and open source, and has a plugin architecture.
A program typically has to be designed to look for a plug-in, and the plug-in has to have a standard access point to accept control from the main program. Every application or website does it a little differently.
The simplest type of plug-in is accessed something like this:
if (a plug-in exists/is configured)
call predefined plug-in code
In this case, the main program is coded to only handle a specific set of plug-ins (many php-based wordpress templates are like this). A slightly more advanced plug-in
perform application specific logic
if any plug-in exists that exposes the run_after_app_specific_logic function
call plug-in code
This second case can handle ridiculously complex plug-ins ... the plug-in would just need to implement more functions called by the master program.
Eclipse in an example of a application-framework which is entirely plugin-based, meaning that all functionality is implemented as plugins. There is a thin layer at the bottom for startup/shutdown and plugin-management, but everything else is implemented as plugins on top of that. This results in a framework which can be used for just about everything. More info about Eclipse plugin architecture can be found here: http://www.eclipse.org/articles/Article-Plug-in-architecture/plugin_architecture.html.
It's very language dependent.
In an interpreted language it simply involves calling a file that follows a pattern.
In C it's pretty hard to do without help. In C+windows a "DLL" can be a plug-in and are often used that way.
In an OO language with reflection, you might create an object that implements an interface and load it reflectively. After it's loaded, you can ignore the fact that it was a plug-in because it's treated as any other object in your code.
.net has a plugin architecture (is it COM?) Well anyway COM can be used as (is?) a plugin system.
Your question is probably too open-ended because of all the possibilities. There is no single answer.
I've never written a plugin system. But this is how I imagine it in my head:
Your program has a subdirectory for plugins (e.g. "C:\Program Files\My Program Name\plugins").
You create plugins as DLL files and place them in the plugins folder.
These DLLs would export functions with predefined names.
When you run your program, it looks through all the DLLs in your plugins folder. In each one it would look for an exported function with a certain name (e.g. "Load") and call that function. The plugin could then do any setup that it needed to do.
The program would then call an exported function on the plugin with a name like "GetPluginName". The plugin would return it's name and the program could then use that name when it displays a list of plugins to the user.
When it comes time to invoke the plugin, the program would call another exported function (maybe "Activate") and probably pass the plugin a pointer to the data that the plugin is going to work on. The program would then do its work on the data.
The plugin might also export another function that the program would call to show a setup dialog where you could change the plugin options.
A plugin system can be implemented in many ways, but the common way for a lot of C/C++ applications is a DLL-based plugin SDK.
The DLL will expose various automated function calls which may allow the plugin to "set itself up" in the running application such as adding menu items, new functionality or extra options for systems (like 3D rendering implementations).
More ofthen there's no need for any special discovery - the plugin mechanizm is generally dumb: Here's a code signature I understand, and here's a call(s) I can make. I have no clue how the thing I'm calling will do the job, but I expect result to be in certain format. And that is pretty much a contract. Now - the plugin will implement the contract and make itself available. In Java, for example "make available" simply means that implementing classes are loaded into memory. JDBC driver for a particular database would be a good example.
I see a lot of questions, both here on SO and elsewhere, about "maintaining
common libraries in a VCS". That is, projects foo and bar both depend on
libbaz, and the questioner is wondering how they should import the source
for libbaz into the VCS for each project.
My question is: WTF? If libbaz is a library, then foo doesn't need its
source code at all. There are some libraries that are reasonably designed
to be used in this manner (eg gnulib), but for the most part foo and bar
ought to just link against the library.
I guess my thinking is: if you cut-and-paste source for a library into
your own source tree, then you obviously don't care about future updates
to the library. If you care about updates, then just link against the
library and trust the library maintainers to maintain a stable API.
If you don't trust the API to remain stable, then you can't blindly
update your own copy of the source anyway, so what is gained?
To summarize the question: why would anyone want to maintain a copy of a
library in the source code for a project rather than just linking against
that library and requiring it as a dependency?
If the only answer is "don't want the dependency", then why not just
distribute a copy of the library along with your app, but keep them
totally separate?
The use of vendor branches to control 3rd party dependencies is discussed in some depth in the Subversion book. As I understand it, the basic advantages are guaranteeing a stable API and uniformity of libraries for all developers, and the ability to control custom modifications in house in the same versioning system.
On the project I'm working on right now, we've got the main code (which is in one Subversion project) and a host of assorted libraries from various places that are in their own Subversion modules. The Visual Studio solution maintains separate projects for each of them and links them together at the end. If we were working on Unix or similar OSs, we'd do the same thing.
The only downside I see is that I sometimes forget to update one of the libraries that changes more frequently, and my code doesn't compile until I notice that. If we had the libraries in the same module, then we wouldn't have that problem. (Not that I'd ever do it that way. The gains in flexibility and the ability to use different libraries with different main projects are just too great.)
The API is a red herring here: either it stays the same or it changes, and if it changed we'd have to update the main code either way. So is the question of source vs. binary libraries (either we compile them with the main project, or we don't).
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I've met quite a few people lately who says that 3rd party libraries doesn't belong in version control. These people haven't been able to explain to me why they shouldn't yet, so I hoped you guys could come to my rescue :)
Personally, I think that when I check the trunk of a project out, it should just work - No need to go to other sites to find libraries. More often than not, you'd end up with multiple versions of the same 3rd party lib for different developers then - and sometimes with incompatibility problems.
Is it so bad to have a libs folder up there, with "guarenteed-to-work" libraries you could reference?
In SVN, there is a pattern used to store third-party libraries called vendor branches. This same idea would work for any other SVN-like version control system. The basic idea is that you include the third-party source in its own branch and then copy that branch into your main tree so that you can easily apply new versions over your local customizations. It also cleanly keeps things separate. IMHO, it's wrong to directly include the third-party stuff in your tree, but a vendor branch strikes a nice balance.
Another reason to check in libraries to your source control which I haven't seen mentioned here is that it gives you the ability to rebuild your application from a specific snapshot or version. This allows you to recreate the exact version that someone may report a bug on. If you can't rebuild the exact version you risk not being able to reproduce/debug problems.
Yes you should (when feasible).
You should be able to take a fresh machine and build your project with as few steps as possible. For me, it's:
Install IDE (e.g. Visual Studio)
Install VCS (e.g. SVN)
Checkout
Build
Anything more has to have very good justification.
Here's an example: I have a project that uses Yahoo's YUI compressor to minify JS and CSS. The YUI .jar files go in source control into a tools directory alongside the project. The Java runtime however, does not--that has become a prereq for the project much like the IDE. Considering how popular JRE is, it seems like a reasonable requirement.
No - I don't think you should put third party libraries into source control. The clue is in the name 'source control'.
Although source control can be used for distribution and deployment, that is not its prime function. And the arguments that you should just be able to check out your project and have it work are not realistic. There are always dependencies. In a web project, they might be Apache, MySQL, the programming runtime itself, say Python 2.6. You wouldn't pile all those into your code repository.
Extra code libraries are just the same. Rather than include them in source control for easy of deployment, create a deployment/distribution mechanism that allows all dependencies to easily be obtained and installed. This makes the steps for checking out and running your software something like:
Install VCS
Sync code
Run setup script (which downloads and installs the correct version of all dependencies)
To give a specific example (and I realise this is quite web centric), a Python web application might contain a requirements.txt file which reads:
simplejson==1.2
django==1.0
otherlibrary==0.9
Run that through pip and the job is done. Then when you want to upgrade to use Django 1.1 you simply change the version number in your requirements file and re-run the setup.
The source of 3rd party software doesn't belong (except maybe as static reference), but the compiled binary do.
If your build process will compile an assembly/dll/jar/module, then only keep the 3rd party source code in source control.
If you won't compile it, then put the binary assembly/dll/jar/module into source control.
This could depend on the language and/or environment you have, but for projects I work on I place no libraries (jar files) in source control. It helps to be using a tool such as Maven which fetches the necessary libraries for you. (Each project maintains a list of required jars, Maven automatically fetches them from a common repository - http://repo1.maven.org/maven2/)
That being said, if you're not using Maven or some other means of managing and automatically fetching the necessary libraries, by all means check them into your version control system. When in doubt, be practical about it.
The way I've tended to handle this in the past is to take a pre-compiled version of 3rd party libraries and check that in to version control, along with header files. Instead of checking the source code itself into version control, we archive it off into a defined location (server hard drive).
This kind of gives you the best of both worlds: a 1 step fetch process that fetches everything you need, but it doesn't bog down your version control system with a bunch of necessary files. Also, by fetching pre-compiled binaries, you can skip that phase of compilation, which makes your builds faster.
You should definitively put 3rd party libraries under the source control. Also, you should try to avoid relying on stuff installed on individual developer's machine. Here's why:
All developers will then share the same version of the component. This is very important.
Your build environment will become much more portable. Just install source control client on a fresh machine, download your repository, build and that's it (in theory, at least :) ).
Sometimes it is difficult to obtain an old version of some library. Keeping them under your source control makes sure you won't have such problems.
However, you don't need to add 3rd party source code in your repository if you don't plan to change the code. I tend just to add binaries, but I make sure only these libraries are referenced in our code (and not the ones from Windows GAC, for example).
We do because we want to have tested an updated version of the vendor branch before we integrate it with our code. We commit changes to this when testing new versions. We have the philosophy that everything you need to run the application should be in SVN so that
You can get new developers up and running
Everyone uses the same versions of various libraries
We can know exactly what code was current at a given point in time, including third party libraries.
No, it isn't a war crime to have third-party code in your repository, but I find that to upset my sense of aesthetics. Many people here seem to be of the opinion that it's good to have your whole developement team on the same version of these dependencies; I say it is a liability. You end up dependent on a specific version of that dependency, where it is a lot harder to use a different version later. I prefer a heterogenous development environment - it forces you to decouple your code from the specific versions of dependencies.
IMHO the right place to keep the dependencies is on your tape backups, and in your escrow deposit, if you have one. If your specific project requires it (and projects are not all the same in this respect), then also keep a document under your version control system that links to these specific versions.
I like to check 3rd party binaries into a "lib" directory that contains any external dependencies. After all, you want to keep track of specific versions of those libraries right?
When I compile the binaries myself, I often check in a zipped up copy of the code along side the binaries. That makes it clear that the code is not there for compiling, manipulating, etc. I almost never need to go back and reference the zipped code, but a couple times it has been helpful.
If I can get away with it, I keep them out of my version control and out of my file system. The best case of this is jQuery where I'll use Google's AJAX Library and load it from there:
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js" type="text/javascript"></script>
My next choice would be to use something like Git Submodules. And if neither of those suffice, they'll end up in version control, but at that point, its only as up to date as you are...
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I am working in a team of five. We are working on a C# application with five csprojects.
The problem is that for each csproject, each of my colleagues has their own ideas on how to reference a DLL; some would like to link in by Project reference, other would like to link in the DLL only. So each and every one of us will have our own csproject.
I want all of them to check in their csproject; but given that every copy of csproject is different, there isn't really a feasible mechanism to do that, is there? But if I don't ask them to check in their csproject, then every time they add a new file, I would have to manually edit my csproject and that's very tedious, not to mention that it beats the purpose of continuous integration.
Is there any strategy to handle this? I know it would be best to enforce a standard, but is there any other option leaving this aside?
There is a reason why the csproject content is different for everyone; not everyone has all of the five csprojects, and not everyone can have all of the 5 csprojects. So invariably some will have to end up having to reference DLLs instead of projects, and some want to reference by projects for the ease of debugging. If I were to enforce a standard, as the answers here suggest, I would have to solve this issue.
As to why we need to split into multiple csprojects, that's because we want to reuse some parts of the code for other applications, and because not everyone can have all access to the source code. It's more political than technological.
Your problem is not how to handle it with Source Control.
Your problem is that you (or management) needs to get your team to adopt a set of standards the entire team follows.
If you let everyone follow their own mish-mash of ideas and do not get team cohesion on the basics it will only end in tears...
You're almost certainly solving the wrong problem. If you fork the .csproj files to cater to invididual preferences, you are incurring additional work and introducing the likelihood of errors, for exactly the reason you describe -- every time Alice adds a file to AlicesX.csproj, Bob has to learn about this and add the same file to BobsX.csproj.
You really need to consider this as a problem of standards and team dynamics: agree on how DLLs will be referenced in the master sources, and require everyone to stick to that. If the "losing" side don't like to work that way, sure, they can use their preferred style in their private working copies. But you really only want one master source, and you want to work towards getting everybody to buy into the way the master source does it.
Per your edit: If you really, really cannot come to an agreement with your colleagues, then I would still suggest a single master, but write a little utility that the dissenters can use that converts project references to DLL references (or vice versa). .csproj files are just XML so this is pretty trivial to do. If you cannot even agree on what is going to be the repository format, then you will need to maintain parallel .csproj files, but I'd still write the utility to ensure that changes made to DllReferencingProj.csproj get copied to ProjectReferencingProj.csproj. But I still say you're just making more work and storing up more pain for yourself than if you had the squabble and got it over with: in order to function as a team, you're going to need to find some way of resolving disputes, and this is as good as test case as any.
Time to make everyone grow up and follow a standard. If you're all working on the same code you should decide together whether referencing the dll or the project is best and then stick to it. Once you guys figure this one out you can decide whether to indent 2 or 4 spaces or a tab. Then decide whether to put your curly braces on the same line as or the next line after your function declarations. I'm not even going to speak to the vagaries of Hungarian notation...
Our configuration is as follows:
Project -> copy dll to common folder
Project -> copy dll to common folder
Main Project -> Copy exe to common folder, run application from common folder
Doesn't much matter how you reference using this configuration, the dlls will be picked up from the application folder and you're golden.
Continuous integration shouldn't care about your .csproj files. I guess they're MSBUILD files? Or something?
Don't use them for CI. They're junk. They accrue garbage because they make too many things invisible. Create a clean build structure that is independent of them, you'll be thankful you did. And then only check in a project file when you're adding something, and everyone else can update/merge. You don't need to have the same or even similar project files most of the time. On my team we don't even run the same version of VS across all workstations.