I am currently working with python and Qt which is kind of new for me coming from the C++ version and I realised that in the oficial documentation it says that an UI file can be loaded both from .ui or creating a python class and transforming the file into .py file.
I get the benefits of using .ui it is dynamically loaded so no need to transform it into python file with every change but what are the benefits of doing that?, Do you get any improvements in run time? Is it something else?
Thanks
Well, this question is dangerously near to the "Opinion-based" flag, but it's also a common one and I believe it deserves at least a partial answer.
Conceptually, both using the pyuic approach and the uic.loadUi() method are the same and behave in very similar ways, but with some slight differencies.
To better explain all this, I'll use the documentation about using Designer as a reference.
pyuic approach, or the "python object" method
This is probably the most popular method, especially amongst beginners. What it does is to create a python object that is used to create the ui and, if used following the "single inheritance" approach, it also behaves as an "interface" to the ui itself, since the ui object its instance creates has all widgets available as its attributes: if you create a push button, it will be available as ui.pushButton, the first label will be ui.label and so on.
In the first example of the documentation linked above, that ui object is stand-alone; that's a very basic example (I believe it was given just to demonstrate its usage, since it wouldn't provide a lot of interaction besides the connections created within Designer) and is not very useful, but it's very similar to the single inheritance method: the button would be self.ui.pushButton, etc.
IF the "multiple inheritance" method is used, the ui object will coincide with the widget subclass. In that case, the button will be self.pushButton, the label self.label, etc.
This is very important from the python point of view, because it means that those attribute names will overwrite any other instance attribute that will use the same name: if you have a function named "saveFile" and you name the button "saveFile", you won't have any [direct] access to that instance method any more as soon as setupUi is returned. In this case, using the single inheritance method might be helpful - but, in reality, you could just be more careful about function and object names.
Finally, if you don't know what the pyuic generated file does and what's it for, you might be inclined to use it to create your program. That is wrong for a lot of reasons, but, most importantly, because you might certainly realize at some point that you have to edit your ui, and merging the new changes with your modified code is clearly a PITA you don't want to face.
I recently answered a related question, trying to explain what happens when setupUi() is called in much more depth.
Using uic.loadUi
I'd say that this is a more "modular" approach, mostly because it's much more direct: as already pointed out in the question, you don't have to constantly regenerate the ui files each time they're modified.
But, there's a catch.
First of all: obviously the loading, parsing and building of an UI from an XML file is not as fast as creating the ui directly from code (which is exactly what the pyuic file does within setupUi()).
Then, there is at least one relatively small bug about layout contents margins: when using loadUi, the default system/form margins might be completely ignored and set to 0 if not explicitly set. There is a workaround about that, explained in Size of verticalLayout is different in Qt Designer and PyQt program (thanks to eyllanesc).
A comparison
pyuic approach
Pros:
it's faster; in a very simple test with a hundred buttons and a tablewidget with more than 1200 items I measured the following bests:
pyuic loading: 33.2ms
loadUi loading: 51.8ms
this ratio is obviously not linear for a multitude of reasons, but you can get the idea
if used with the single inheritance method, it can prevent accidental instance attribute overwritings, and it also means a more "contained" object structure
using python imports ensures a more coherent project structure, especially in the deployment process (having non-python files is a common source of problems)
the contents of those files are actually instructive, especially for beginners
Cons:
you always must remember to regenerate the python files everytime you update an ui; we all know how easy is to forget an apparently meaningless step like this might be, expecially after hours of coding: I've seen plenty of situations for which people was banging heads on desks (hopefully both theirs) for hours because of untraceable issues, before realizing that they just forgot to run pyuic or didn't run it on the right files; my own forehead still hurts ;-)
file tracking: you have to count two files for each ui, and you might forget one of them along the way when migrating/forking/etc, and if you forgot an ui file it possibly means that you have to recreate it completely from scratch
n00b alert: beginners are commonly led to think that the generated python file is the one to be used to create their programs, which is obviously wrong; unfortunately, the # WARNING! message is not clear enough (I've been almost begging the head PyQt developer about this); while this is obviously not an actual problem of this approach, right now it results in being so
some of the contents of a pyuic generated files are usually unnecessary (most importantly, the object name, which is used only for specific cases), and that's pretty obvious, since it's automatically generated ("you might need that, so better safe than sorry"); also, related to the issue above, people might be led to think that everything pyuic creates is actually needed for a GUI, resulting in unnecessary code that decreases its readability
loadUi method
Pros:
it's direct and immediate: you edit your ui on Designer, you save it (or, at least, you remember to do it...), and when you run your code it's already there; no fuss, no muss, and desks/foreheads are safe(r)
file tracking and deployment: it's just one file per ui, you can put all those ui files in a separate folder, you don't have to do anything else and you don't risk to forget something on the way
direct access to widgets (but this can be achieved using the multiple inheritance approach also)
Cons:
the layout issue mentioned above
possible instance attribute overwriting and no "ui" object "containment"
slightly slower loading
path and deployment: loading is done using os relative paths and system separators, so if you put the ui in a directory different from the py file that loads that .ui you'll have to consider that; also, some package managers use to compress everything, resulting in access errors unless paths are correctly managed
In my opinion, all considering, the loadUi method is usually the better choice. It doesn't distract me, it allows better conceptual compartmentation (which is usually good and also follows a pattern similar to MVC much more closely, conceptually speaking) and I strongly believe it as being far less prone to programmer errors, for a multitude of reasons.
But that's clearly a matter of choice.
We should also and always remember that, like every other choice we do, using ui files is an option.
There is people who completely avoids them (as there is people who uses them literally for anything), but, like everything, it all and always depends on the context.
A big benefit of using pyuic is that code autocompletion will work.
This can make programming much easier and faster.
Then there's the fact that everything loads faster.
pyuic6-Tool can be used to automate the call of pyuic6 when the application is run and only convert .ui files when they change.
It's a little bit longer to set up than just using uic.loadUi but the autocompletion is well worth it if you use something like PyCharm.
I read on this answer the following statement:
"Keep in mind that the compiler can and does move code from one chunk into other chunk output files if it determines that it is only used by that chunk."
Is there any way to switch that off?
I have a 'main' chunk and an 'optional' chunk, and I'm finding the code from the optional chunk is being moved entirely into the main.
My optional code will only be called from the main code, but only if it's determined that we actually want to load the optional stuff (based on a flag that's external to both.)
I want to minimize the size of the main code for cases where the optional stuff isn't needed, but it doesn't seem to be possible with closure as far as I can see.
EDIT:
To split the code I use the -chunk options on the (java) commandline. The 'main' one I point at several folders ('src/Infra/*.js' etc) and use 'auto' for the numFiles for the chunk. The 'optional' I point at three specific files, no wildcard, and specify 3 as numFiles.
To load the 'optional' script the 'main' writes a script tag to the page and has a Promise resolve when it loads. 'optional' is supposed to instantiate the class it defines, and push a reference to that instance to an array in the global namespace, then main reads the ref from the array, and calls an init() method on it, passing in some dependencies.
Is there a better-supported (and equally compact) way of doing it?
EDIT2: in case anyone has a similar issue, I resolved it using the "nameCache" feature of uglifyjs, so the separate components don't necessarily need to be compiled at the same time.
The compiler does not move code "up" the module graph. What's happening is the compiler somehow believes that symbols defined in your optional chunk are directly required.
This most frequently occurs because you are using dependency management and modules. When the compiler sorts dependencies, if any of the "optional" files are directly imported via require for CommonJS, import for ES6 or goog.require for Closure. In this case the compiler adds them to the main module.
To be more specific, I'd actually have to see code.
I am trying to make changes to the behavior of a function and print the results to a file. The ViewCfg plug-in described in the Plug-in Development Guide does something similar, but I am trying to avoid having to use Ast.get, which ViewCfg uses. I am thinking of extending Printer.extensible_printer which, according to the Frama-C API Documentation, is something I can do if I want to obtain a custom pretty-printer.
However, if I extend the pretty-printer as described in the API docs, unless I'm doing something wrong, I notice that the changes I make take place regardless of which project is set as the current project. I'm using File.create_project_from_visitor to create a new project and Project.set_current to set the new project as the current project before I use the custom pretty-printer.
Is it true that any change made by a class that extends Printer.extensible_printer applies to all projects? I happen to be using frama-c-Aluminium-20160502, which I know is not the latest version.
EDIT: Sorry, I should have made this clearer in the beginning, but I'm not actually making changes to the behavior of a function. I'm reading in the behavior of a function, then based on that, I'm trying to generate as output valid C code that's meant to be read as input by another program.
Regarding AST.get, the only reason I was avoiding it was that it sounds like it gets the entire AST, while I'm only interested in part of it, i.e. behaviors. But if I'm just making things harder for myself by avoiding it, then I'll go ahead and use it.
VS2015 shows how many references there are to a class.
However if the class is started by WebApplication.Run the references are not shown.
The highlighted code does get executed when the application is run.
Is there any way to get the reference count for the Configure method?
Here are two reasons ;)
The Startup Class is invoked by reflection (it does not implement an interface)
I doubt that code pieces outside of your local source code will influence the reference count. So even if somewhere deep in WebApplication.Run the Configure method is invoked (assuming directly over some magic interface), the reference code will not rise. Make sense, otherwise the counter for string would have overflow ;)
I’m curious to know how feasible it is to get away from the dependency onto the application’s internal structure when you create an automated test case. Or you may need to rewrite the test case when a developer modifies a part of the code for a bug fix, etc.
We could write several automated test cases based on the applications internal object structure, but lets assume that the object hierarchy changes after 6 months or so, how do we approach these kind of issues?
I can't speak for other testing tools but at least in QTP's case the testing tool introduces a level of abstraction over the application so that non-functional changes in the application often (but not always) have no effect on the way the testing tool identifies the object.
For example in QTP all web elements are considered to be direct children of the document so that changes in the DOM (such as additional tables) don't change the object's description.
In TestComplete, there are a couple of ways to make sure that the changed app structure does not break you tests.
You can set up the Aliases tree of the Name Mapping feature. In this case, if the app structure is changed, you need to modify the Aliases tree appropriately and your test will stay working without requirement to modify them.
You can use the Extended Find feature of the Name Mapping in order to ignore parts of the the actual object tree and search for a needed objects on deeper levels.
This is what I was forced to do after losing all my work twice due to changes on the DOM structure:
Every single time I need to work with an object, I use the Find function with the ID of the object, searching for the object on the Page object. This way, whenever the DOM gets updated, my tests still run smoothly.
The only thing that will break my tests is if the object's ID get changed, but that's not very probable to happen.
Here you can find some examples of the helper functions I use.