In a Rails 3.1 app, one controller needs to have all its views compile whatever Sass stylesheets they might need per request using a set of custom variables. Ideally, the compilation must happen via the asset pipeline so that content-based asset names (ones that include an MD5 hash of the content) are generated. It is important for the solution to use pure Sass capabilities as opposed to resorting to, for example, ERB processing of Sass stylesheets.
From the research I've done here and elsewhere, the following seems like a possible approach:
Set up variable access
Create some type of variable accessor bridge using custom Sass functions, e.g., as described by Konstantin Haase here (gist). This seems pretty easy to do.
Configure all variable access via a Sass partial, e.g., in _base.sass which is the Compass way. The partial can use the custom functions defined above. Also easy.
Capture all asset references
Decorate the asset_path method of the view object. I have this working well.
Resolve references using a custom subclass of Sprockets::Environment. This is also working well.
Force asset recompilation, regardless of file modification times
I have not found a good solution for this yet.
I've seen examples of kicking off Sass processing manually by instantiating a new Sass::Engine and passing custom data that will be available in Sass::Script::Functions::EvaluationContext. The problem with this approach is that I'd have to manage file naming and paths myself and I'd always run the risk of possible deviation from what Sprockets does.
I wasn't able to find any examples of forcing Sprockets processing on a per-request basis, regardless of file mod times, that also allows for custom variable passing.
I'd appreciate comments on the general approach as well as any specific pointers/suggestions on how to best handle (3).
Sim.
It is possible. Look here SASS: Set variable at compile time
I wrote a solution to address it, I'll post soon and push it here, in case you or someone else still need it.
SASS is designed to be pre-compiled to CSS. Having Sprockets do this for every request for a view on a per request basis is not going to perform very well. Every request is going to have to wait for the compilation to be done, and it is not fast (from a serving-pages point of view).
The MD5 generation is within Sprockets, so if you are changing custom variables you are going to have to force a compilation on every single request to make sure that changes are seen because the view is (probably) not going to know.
It sounds as though this is not really in the sweet-spot of the asset-pipeline, and you should look at doing something more optimised for truly dynamic CSS.
Sorry. :-)
Related
I would like to use Sorbet in my Ruby projects at work. As I want to make the process as smooth as possible, I'd like to know if it is possible to add static type checking only using RBI files in sorbet folder.
The idea is to avoid adding signatures to the source code, so my colleagues do not complain, then adding signatures in RBI on the side. This way I can start typing and benefiting in my local environment until it is advanced enough.
Thanks
Yes, it's possible for static checking but not for runtime checking. But I think it's enough for your use case
Considering all freedom that yocto gives to the developer, I have a question.
I would like to make this my_file.inc available only for recipes in one particular meta-layer. I know, that, for instance, using INHERIT keyword inside the local.conf will make my_class.bbclass file available globally for each recipe.
Is it a good practice to add this:
require my_file.inc
inside layer.conf? Or should I change my_file.inc to the my_file.bbclass, and, add INHERIT = "my_file.bbclass" to the layer.conf?
Any other possibilities?
Even if it seems to work, neither of your approaches is technically completely correct. The key point is that all .conf files are parsed first and everything they contain is globally visible throughout the whole build process. So if you add something through the layer.conf file, itis not being pulled in through an unexpected place, it also is not being limited that layer only and might therefore cause breakage at other places.
While I do not have a really good and clean solution, maybe the following can help you:
You can make your custom recipes react on certain keywords in DISTRO_FEATURES or MACHINE_FEATURES. Then you can create a two-staged approach:
Add the desired keyword in local.conf (or your MACHINE, or DISTRO, or whatever configuration)
Make the recipes react to it. If you need the mechanism in several places, then it might be useful to pour it into a .bbclass that your layer brings along and that you pull in for the respective recipes.
This way the effect is properly contained.
Maybe part 5.1.3.2 from the Yocto Project answers your question:
Avoid duplicating include files. Use append files (.bbappend) for each recipe that uses an include file. Or, if you are introducing a new recipe that requires the included file, use the path relative to the original layer directory to refer to the file. For example, use require recipes-core/package/file.inc instead of require file.inc. If you're finding you have to overlay the include file, it could indicate a deficiency in the include file in the layer to which it originally belongs. If this is the case, you should try to address that deficiency instead of overlaying the include file. For example, you could address this by getting the maintainer of the include file to add a variable or variables to make it easy to override the parts needing to be overridden.
So to avoid duplicate inclusion later, it would be better not to include your .inc file(s) this way.
I'm using ng-bootstrap in my Angular project.
The problem is that ng-bootstrap is still in its early stages and missing lots of functionality. I have added a simple feature within the code in my node_modules/#ng-bootstrap directory.
The trouble is that I worry that if/when there is an update to ng-bootstrap and I update my project with it, my local changes in the functionality will be overwritten and lost.
What are some techniques to deal with this problem?
You've effectively just created your own "branch" of that package. You could submit a pull request if the functionality is something that should be there for everyone. Since you have custom changes, you're responsible for making sure updates don't overwrite them.
If i needed to so something like this, i'd see if there was a way to implement the changes without modifying the ng-bootstrap files themselves. Without knowing what the change is, i can't say how that might be accomplished. One option there is to not use a package manager for that framework, or let the package manager get the "official" files, and then copy them somewhere else that you actually use. You're still responsible for making sure to merge changes in when the framework updates, but at least it won't be automatically overwritten.
if I'm using rails 3 which uses asset pipeline to compile all
Javascripts, does that mean I can have only one Knockout view model for my entire application? If not, how do I specify which view model is binded with which view? In the tutorial code, it looks like 1 view model is bound per page, but that doesnt work in rails since all JS are loaded upon first page load.
No, you do not need to include all javascript on every page! This is a very bad idea.
There are many methods for limiting javascript to a single page, you should pick one:
Method 1
Method 2
Method 3
Please, please, please do not try to load all your javascript on every single page.
Update (after your comment below):
I think you are confusing a few different things here.
First, even if you compile all your javascript into a single gzipped/uglified file, that still doesn't force you to use one knockout viewmodel for your entire application. That file can contain multiple viewmodels. They don't even need to know about each other.
Second, the way the rails pipeline works is by concatenating related or dependant javascript files together. It does this to reduce the number of requests the browser has to make to get the javascript it needs for each page. It doesn't necessarily mean all your javascript becomes one file. Just that the javascript for each page become one file. For more information, check out the Rails Asset Pipeline Documenation, it has a great explanation of how it works and how to use it properly.
Third, neither of these things mean you need to write all your javascript as if it were one file. In fact, this is a bad idea. You should seperate your javascript into relevant files by functionality. This allows them to be reusable, as well as eases development work.
My application has a plugin system that allows my users to write their own plugins that get loaded at runtime. Usually this is fine but in some cases two plugins use the same libraries that will cause a collision between those two.
Example:
Plugin A wants to use TouchJSON for working with JSON and thus the creator adds the TouchJSON code to the plugin source and it gets compiled and linked into the plugin binary. Later Plugin B also wants to use that same library and does exactly the same. Now when my app loads these two different plugins it detects this and spits out an warning like this:
Class CJSONScanner is implemented in
both [path_to_plugin_a] and
[path_to_plugin_b]. One of the two
will be used. Which one is undefined.
Since my app just loads plugins and makes sure they conform to a certain protocol I have no control over which plugins are loaded and if two or more use the same library.
As long as both plugins use the exact same version of the library this will probably work but as soon as the API changes in one plugin a bunch of problems will arise.
Is there anything I can do about this?
The bundle loading system provides no mean to pacifically resolve name conflicts. In fact, we're told to ensure ourselves that the problem doesn't happen, rather than what to do if it happens. (Obviously, in your case, that's not possible).
You could file a bug report with this issue.
If this is absolutely critical to your application, you may want to have bundles live in separate processes and use some kind of IPC, possibly NSDistantObject, to pass the data from your program to the plugin hosts. However, I'm fairly sure this is a bag of hurt, so if you don't have very clearly-defined interfaces that allow for distribution into different processes, it might be quite an undertaking.
In a single-process model, the only way to deal with this is to ensure that the shared code (more precisely, the shared Objective-C classes) is loaded once. There are two ways to do this:
Put the shared code in a framework.
Put the shared code in a loadable bundle, and load the bundle when the plug-in is loaded if the relevant classes aren’t already available (check using NSClassFromString()). The client code would also have to use NSClassFromString() rather than referring to classes directly.
Of course, if you aren’t in control of the plug-ins you can’t enforce either of these schemes. The best you can do is provide appropriate guidelines and possibly infrastructure; for instance, in the second case the loading could be handled by the application, perhaps by specifying a class to check for and the name of an embedded bundle to load if it isn’t available in the plug-in’s Info.plist.