Load pre-compiled dart code at runtime using a shared library - dart

Let's assume I have the following project structure:
interfaces/
A.dart, B.dart, etc
app/
main.dart, etc
addon1/
Aimpl.dart, Bimpl.dart, etc
addon2/ etc
The code being executed lies in app/, with some features using the functionalities defined in the interfaces located under interfaces/. However, the actual implementation of those interfaces lie in various addonX/ folders, whose code ONLY accesses code in the interfaces/ folder. The name of that folder might be a bit misleading, really it should be shared/, as my addon/ code is also allowed to instantiate classes from there and so on.
When I compile my app this way, everything works fine - after all, it's all the same project.
However, I would now like to essentially "outsource" the whole code in the addon folders, initially only compiling my interfaces/ and app/ code, and then loading various implementations (which can therefore be chosen by the user) at runtime.
In essence, I would like to have a plugin system where each plugin has access to all interfaces and functionalities in a shared folder (the shared folder would, in essence, be the SDK of my project), similar to how it can be done in Java with the usage of pre-compiled jar files. About a decade ago I saw one implementation of this system that I quite liked in the Bukkit project.
Is there a simple way to achieve this in dart? I've seen some talk about plugins in dart on stackoverflow already, but it took a much different form, with plugins "communicating" with the main app via messages, which is, imo, incredibly cumbersome.

Related

What is the difference between a unity plugin and a dll file?

i am new to Unity and i am try to understand plugins. I have got the difference between a managed plugin and a native plugin, but what is not very clear to me is:
what is the difference between a plugin and a dll? what should i expect to find in an sdk to make it usable in my unity project?
Thanks a lot
To expand on #Everts comment instead of just copying it into an answer, I'll go a little into details here
What is a plugin?
It's a somewhat vague word for a third-party library that is somehow integrated with the rest of your game. It means that it neither is officialy supported by Unity, nor is it a part of your core code. It can be "plugged" in or out without altering its internals, so it must provide some kind of API that can be used by the game code.
For example, you'll find many plugins that handle external services like ads, notifications, analytics etc. You'll also find a couple of developer-tools that can also be called plugins, like tile-based map editors and such.
Plugins come in many forms - DLL files are one example but some plugins actually provide full source code for easier use. And of course, other plugins will provide native code for different platforms, like Objective-C for iOS or .jars for Android.
So to answer your first question:
DLL is simply a pre-compiled source file that can be a part of a plugin
A plugin is a whole library that can consist of multiple files with different formats (.cs, .dll, .jar, .m etc)
What do you need to use an sdk?
First of all - documentation. Like I said before, and like you noticed yourself, not all plugins give you access to the source code. And unfortunately, not many sdks have extensive and developer-friendly documentations so it can be a tough task to actually understand how to use a given sdk.
Secondly - the code. Many sdks give you some kind of "drag & drop" library, a single folder with all the neccessary files inside that you simply add to your Unity projects. I've also seen sdks that use Unity packages that you have to import via Assets > Import Package > Custom Package.
Once you have the code and documentation it's time to integrate it with your game. I strongly recommend using an abstract lyer in your game as, in my experience, you often have to change sdks for various reasons and you don't want to rewrite your game logic every time. So I suggest encapsulating sdk-related code in a single class so that you have to change only one class in your code when switching from, say, one ad provider to another (and keep the old class in case you need to switch back).
So you basically need three things:
Documentation (either a readme file or an online documentation)
The code (precompiled or source)
A versatile integration

How do I convert a specific controller to a package to include in other projects?

VS2013, MVC5, VB
I am nearing the completion of a small project to manage the roles tables in a standard MVC5 application. The code is pretty much encapsulated. What are my options for using this 'package' in other projects?
Can I compile it into something? I know this type of action is possible, I'm just not familiar with the options available to me or the steps to do this. Links to sites that have tutorials are fine. Is creating a Nu Get package the only way to go, or is that even in the ballpark of what I'm asking. I say Nu Get, but I don't mean for public consumption, only for my consumption.
Will the finished 'whatever' include it's controller class, view models and views? Will I be able to easily manage updates? etc.
Creating a Nuget package is one way. I have created a local repository of common utilities for this purpose. But I usually use it just for DLLs. I use Nuget Package Explorer for its ease of use since its just me using the packages most of the time. Not sure its possible to place the files in specific directories.
Files in the content folder are copied to the root of your application when the package is installed. - Nuget
The alternative is to create an item template. I used to use this method for class files I want in my code but I can't see why you couldn't do it for the rest. Works well and isn't too hard to set up. There are dozens if not 100s of tutorials on the subject. Here is one on code project.

Using EXE's instead of DLL's as plugins - Ways to "one way, one time" transfer information

tldr; at bottom.
Ok, so once again an interesting problem and I'm looking for a fun and interesting solution.
My current project involves being very modular, meaning the program functionality will be easily changed based on different modules and the program would adapt.
So I started out with the typical route, which is using DLL plugins. Now this is just way to normal, I want to think outside the box a bit.
The modules included in my program are long running campaigns that may take weeks to finish, and there will be many running at a time. So stability is a big issue, so I thought about what Google Chrome does. Processes, not DLLs or threads.
So I have a framework going and I need a way to get some information about each module (which are now EXEs). Now for my DLL framework I was exporting a "Register" function that would fill in some information.
So I thought to myself, hey EXEs can export functions, let's see if that actually works...It doesn't. I did some research into how Windows handles theses things and I don't feel like hacking the PE headers on the fly (but it's the out of the box kind of thinking I'm going for).
I'm planning on using named pipes and CLI parameters to transfer data between the main program and the module exe's. I could use that in a register fashion, but I want to here other peoples thoughts.
tldr: I'm using EXE's instead of DLL's for plugins. Looking for a way to easily export one time information like a exported "Register" function would on a DLL. Thoughts?
You might still consider having the modules written as DLLs with defined entrypoints (e.g., the Register function). Then you write the executable that loads the specified DLL. Your main application would fire off the driver executable and give it a name of a plugin DLL.
That way it is still easy to define and export the set of APIs that must be provided yet still run it as a separate process. The one executable that you write can load the specified DLL and then handle the necessary IPC with the main app.
You could define a protocol via the stdin/stdout, named pipes, sockets, etc.
I have successfully used 'plain' COM for several projects, and objects inheriting from TAutoObject. The bonusses here are IDL; the interopability with .Net, VBA and other non-Delphi things; and the fact that implementors still can choose wether to supply a DLL, an exe, an NT-service, and optionally run hosted over the network (COM+/DCOM). There may be several considerations you should handle about multi-threading and locking, but I found all that I needed to know online.
You can, of course, not use symbols exported by a (running) exe since it is running in another boundary. But, you can load an exe as an image (as you would do with a library) using LoadLibrary(Ex) and then, use the functions exported by the exe. I have tested (just for fun) when debugging PeStudio. See the snapshot below of chrome.exe loaded in the process space of PeStudio.exe using LoadLibrary.

In Delphi, should I add shared units to my projects, to a shared package, or neither?

This question is similar to this one, but not a duplicate because I'm asking about issues not discussed in that question.
I have a client-server project in Delphi 7 with the following directory structure:
\MyApp
\MyClientApp
\MyServerApp
\lib
There are 2 actual Delphi projects (.dpr), one each in the MyClientApp and MyServerApp folders.
The lib folder has .pas units that have common code to the client and server apps. What I'm wondering is if I should include those .pas files in the client and server projects? Or should I create a package in the lib folder which includes those units? Or should I just leave the .pas files sitting in the lib folder and not add them to any app/package?
What are the pros/cons of each approach? Which way is "best"? Is there any issue with having those units from the lib folder be included in more than one project?
Right now the units in the lib folder are not a part of any app/package. One disadvantage of this is that when I have my client app open in Delphi, for example, and I want to search in all files in the project for something, it doesn't also search in the units in the lib folder. I get around this by opening those units and doing a find in all open files, or using grep search (but I'd prefer a better solution).
I would also greatly prefer a solution where I will not have to go and open some separate package and recompile it when I make changes to those files in the lib folder (is this where I should use a project group?).
Sharing units between applications always carries the risk of incompatible changes done in one application that breaks the other. On the other hand, making copies of these units is even worse, so your approcach of moving them to their own subdirectory at least adds a psychological barrier to changing them without considering other programs.
As for adding them to the project files: I usually add some units which I frequently access (either for expanding or for reference) from the IDE to the project, and leave others out for the compiler to pick using the search path. I do that on per project basis, that means, some units may be part of several projects, why not?
Putting them into a package only makes sense, if you actually want to create a package based application, otherwise, why bother?
For more info on how I organize my projects and libraries, see http://www.dummzeuch.de/delphi/subversion/english.html
I dislike having files shared by projects. All too often, you'll be tempted to edit one of the shared files, and you'll either break something in the other project, or you'll forget that you have to rebuild the other project at all.
When the shared files are instead separated into their own library (package), then there's a little extra barrier to editing them. I consider that a good thing. It will be a light reminder that you're switching from project-specific code to shared code. You can use project groups to let you keep every together in a single IDE instance. arrange the library projects ahead of the executable projects. The "build all" command will build everything in order, starting with the first project.
Keep your DCU files separate from your PAS files. You can do this easily by setting the "DCU output directory" project option to send your package's units to some other location. Then put that destination directory on your other projects' "search path." They'll find the DCU, but they won't find the PAS file, and so no other project will accidentally recompile a unit that isn't really a member.
Having a separate package also discourages use of project-specific conditional defines. Those cause all sorts of trouble when you're sharing units between projects. Find a way to instead keep all project-specific options within the respective projects. A shared library shouldn't require project-specific modifications. If a library needs to act differently based on who's using it, then employ techniques like callback functions that the library user can set to modify the library's behavior.
I would need to have a very good reason to add shared code to a package. If you just have a few shared files stick them all in a directory called Shared. This should make it obvious the files are shared between projects.
Also use a good build tool to do automated builds so you will find out soon enough if you break something.
.bpl files are fine for components, but bring in serious added complexity for things like this, unless you have a huge amount of shared files.
I usually create a package with all shared unit, and just use the units.
If you do not explicitly mark "Build with run time packages" the package content (all used dcu's) will be linked to your project as any other unit.
I would only use runtime packages if you actually had two binaries that were supposed to run on the same physical machine and that shared some code. Keep in mind that runtime packages are mostly an all-or-nothing approach. Once you decide to use them you will also no longer be able to link the RTL and VCL units straight into your projects and will instead have to deploy those separately as well.
However, packages might still be a good solution to your problem when combined with project groups which is exactly what I'm doing. I hate having shared units included in multiple projects. Including the shared units in a package (but not compiling your actual projects with runtime packages) allows you to add that package to your project group so you (and the IDE!) will always have them easily accessible yet nicely separated from the project-specific code. Strictly speaking you don't even ever have to compile those packages. They can merely serve as an organisational unit in the project manager.
Note that for the Find in Files, you can also specify "in all files in project group"

Organizing the search path

We create via "Tools | Options | Environment Variables" Variables like that:
$(Sources) = D:\Sources\Delphi
$(OurLib) = $(Sources)\OurLib\Src
$(OurApp1) = $(Sources)\Applications\App1\3.x
$(ThirdParty) = $(Sources)\ThirdPartyComponents
We use these Variables in the project search path like that:
($OurApp1)\Src\Core;($OurApp1)\Src\GUI;($OurApp1)\Src\Plugins;$(ThirdParty)\JVCL
But this is broken (meanwhile fixed) since Delphi 2009 as these variables are not evaluated completely anymore (see QC #73276). So the files in the directories are not found by the compiler. A workaround: Use only complete directories in the environment variables.
We use this approach because on all developer machines and the build servers the files can be found and we only have to point $(Sources) to the right place.
We don't have anything in our global library path (except the Delphi defaults), because that wouldn't be in the version control and isn't reflected on other developers or build machines.
One problem is: If one unit in $(OurLib) decides to include another new unit maybe in a new path, all projects break because they don't find this new unit. Then we have to go through all projects and add the search path. (BTW: I really hate the search path editor...wouldn't be a simple memo field much better to edit than this replace/add/delete logic?)
Another thing we do is not adding many units to our project. Especially everything from $(OurLib), but we often have units like plugins which add functionality only by including them. For different editions of our products, we want to include different units. As Delphi always messes up $IFDEFs in the uses clause in the .dpr we help us by including units named like "IncludePlugins" which then include the units depending on IFDEFs.
But not including units in the project makes navigating to a pain. The units don't appear in the project, they are not found by Ctrl+12 (Show Units), they are not shown in code completion etc.
Has anybody a better way to cope with these problems?
We use only relative paths, any libraries are always below the libs subdirectory while the project source code resides in the src subdir. So our search paths always look like:
..\libs\library1;..\libs\library2\common;
etc.
All libraries are added as svn:external to each project, so checking out the project will automatically check out the libraries as well and the search path will always point to the correct version of the library for that project.
Not perfect, but it works most of the time.
I have to agree about the search path editor, it is even worse for relative paths because you must not use the "..." buttons otherwise Delphi will insert an absolute path.
We use standard drive mappings.
Our current project is always on W: regardless if it is a network drive or a substitute.
This works great.
When you need to work on a different project, swap the W: and you can continue.
You can copy the search path out to an editor, modify it and then copy it back.
Your search path is much too big. It should contain only the things you want Delphi to recompile with your project. You don't really want to recompile the Jedi VCL every day, do you?
I create a single directory where all compiled units go. Say, C:\dcu. Specify that as the "unit output directory" in all packages. My "search path," then, is always just this:
$(Delphi)\Lib;C:\dcu
The compiler finds everything it needs, and it never finds any source code. The only source code it ever sees is in the files that directly belong to whatever project I'm compiling. The project's own source directories don't need to be on the search path because all of those files are already direct members of the project. The compiler knows exactly where they are.
For me, all a project's source files go in a single directory. If you want separate directories for different parts, like Core and GUI, then I would put those in separate packages so I could work on them and compile them separately. Even if the final program doesn't use the resultant BPLs, packages are still a good way of segmenting your project and defining dependencies.
When compiling units for one project doesn't automatically compile units for all the other projects, you're forced to change active projects. It takes a moment of your time, but it also serves as a mental reminder that you're "changing hats," too.
Although you're producing just one product, that doesn't mean you should have just one project in Delphi. You should have at least one project for each executable module (EXE, DLL, BPL) in your product. Use project groups to manage multiple projects in a single IDE session. No unit should be a member of more than one project.
I don't understand your part about plug-ins and different editions of your project. When you say "plug-in," I assume you're talking about separate executable modules, like DLLs or packages, that the customer can choose to include or not. Couldn't you turn your different editions' features into plug-in modules that simply don't include in the lesser editions? Then you don't have to worry about conditional compilation of your project; just have several different installer packagers that grab different sets of plug-ins.
I have always found it odd that this has never been addressed adequately. I suggested recently to David I that Delphi should allow the user to set up some sort of preferred development structure and that third party library publishers could be made aware of this so that they could automatically adjust their installers to install correctly in the preferred development framework. If the preferred development structure was stored in an XML file or similar, then, it could be copied from one computer to another on a development team.
As an alternative, it could make an interesting project to create a Delphi application that would allow a user to "refactor" their library installation in a high level way. You specify which folders on your system contain source or compiled components or whatever and where you want to keep source files or compiled units, hit Go and your system gets rearranged for you, while updating your Delphi environment so that when you start Delphi, it finds everything it should.
I've just recently discovered a way to have project specific environment variables in delphi builds using XE6, it's not quite as good as a full blown #define like in C but at least I can now have consistent search paths across multiple projects and create some shared option sets.
What I've done is setup environment variables in the same manner as the original poster and then override them in the dproj or optionset.
The BuildPaths.optset added to the project looks like
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<SVN_Root>..\..\..</SVN_Root>
<SVN_Riemann>$(SVN_Root)\Riemann</SVN_Riemann>
<SVN_Library>$(SVN_Root)\Library</SVN_Library>
<SVN_ThirdParty>$(SVN_Library)\Third Party</SVN_ThirdParty>
</PropertyGroup>
<ProjectExtensions>
<Borland.Personality>Delphi.Personality.12</Borland.Personality>
<Borland.ProjectType>OptionSet</Borland.ProjectType>
<BorlandProject>
<Delphi.Personality/>
</BorlandProject>
<ProjectFileVersion>12</ProjectFileVersion>
</ProjectExtensions>
</Project>

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