So far all of my view code is still in my main file, Main.elm. Within that file, it's relatively well-factored, with the different parts of the view broken down appropriately.
My question: I'd really like to break it out into separate files, e.g.:
- Views/Header.elm
- Views/InfoPage.elm
- Views/Footer.elm
- etc
But I'm really not clear on how to do this. Sure, I can make the different files and import/export the functions that I need. Not difficult with very simple views (e.g. a footer), but I quickly ran into problems with more complex views most of which contain app logic, i.e. calls to the update function. Of course, if I then import the Msgs to my separate view files, then I get a circular dependency. Apologies if this is a naive question, but how do I solve this? I just want to be able have different page sections in different files, it's so much easier for me to navigate like that than perma-scrolling around.
I've googled around and read a few posts about refactoring Elm apps (for example), but nothing focused specifically on the view code. Can anyone give me some pointers? Is it not possible to break out view code without also factoring out the app logic that it uses? (And what if that app logic is used elsewhere too?) I'd really appreciate some help here.
You can organize your dependencies as follows:
Model.elm (includes Model and Msg)
^ ^
| |
View.elm Update.elm
^ ^
| |
Main.elm
You say that you "ran into problems with more complex views, most of which contain app logic, i.e. calls to the update function." But views should not contain app logic and do not call the update function. Views only need to declare what Msg constructor to use to handle various events, so view and update are completely decoupled.
I see a lot of javafx code something like this:
private Button getButton(){
Button myButton = new Button("A button");
myButton.setOnAction...
}
private HBox toolbar(){
Button file = new Button("File");
Button edit = new Button("Edit");
Button props = new Button("Properties");
HBox toolbarArea = new Hbox();
toolbarArea.getChildren().add(file, edit, props);
}
I'm interested in an explanation of why this is done (which I haven't found).
The small method approach works well for internet demo code
Rather than using small methods to define UI elements, the alternatives are:
A very long method unless the application is completely trivial.
FXML defined UI (usually preferred for non-trivial examples, but verbose and unnecessary for small demonstrations).
Separate enclosing objects and classes (sometimes overkill if only aggregation of existing controls is required).
Small methods decrease dependencies on pre-declared objects and program state. Usually the small methods are self-contained and any inputs to them are in their parameter list - it's easier to read and understand them without needing to understand a lot of contextual information and it is also easier to unit test the methods or apply the methods to a more functional programming style, reuse the methods in lambda calls, etc. The names of the small methods also make them self-documenting, so the code is more readable without adding additional comments.
So, in a lot of small, example JavaFX applications you see on the internet, you will find the approach of small methods to describe UI elements, though such an approach is not always the one you should use when you are building larger applications.
Using small methods for UI component definition is an example of an extract-till-you-drop method of programming. Of course, as you can see in the comments on the linked extraction blog, everything is debatable and opinionated, so use your best judgement, but when in doubt, I'd argue in favor or method extraction, not just in the UI definition code, but in your functional code as well.
A concrete example
Take a look at the discussion of JavaFX programming style in the comments on this blog. This is based on this original clock app sample, which does not use small methods, and an updated clock app sample, which is built around many small methods. Per's Lundholm's comment on the original code was this:
A typical sign of not doing it right is when you write comments. Don’t write comments in your code, write code that reads well without comments!
I read you code and I think it is virtually unreadable, with all respect. It is a long method sprinkled with constants that carries little or no meaning. If I am given such a code to change, be it fix a small bug only, I start to extract method ’til I drop. It is the fastest way of understanding code.
I suggest you review both sample code bases and decide which you would prefer to maintain. My guess is that you will decide the version with many small methods would be easier to read and maintain.
Use declarative FXML and CSS for larger applications
Also keep in mind, that for many larger applications, use of FXML and CSS is preferred over java code to define and style the UI elements - this is because a large part of defining a UI is often easier to maintain using a declarative syntax rather than a procedural or functional syntax, and FXML is declarative by it's nature (plus it is fully tooled via SceneBuilder and IDE FXML support). Study the SceneBuilder code base for an example of how to use FXML and CSS to define larger UIs.
i'm currently working on a big projekt and i loose many time searching the right thing in the code. i need to get e.g. a method which makes someting special. so i scroll the whole code.
are there any common and effective methods to struct a file of code? e.g.
1. all global variables
2. constructor etc.
3. all methods
4. all event handlers
do you know common methods to do this??
It's more usual to break large projects into several source files, with logically related functionality. This helps with speeding up compilation and reducing coupling in your design as well as helping you navigate the code.
An example might be to have separate files for
UI functionality
helper classes (such as geometric/maths stuff)
file I/O
core functionality that connects the rest together
Design is a large topic, the book Code Complete by Steve McConnell might be a good starting point for you.
You shouldnt use global variables :)
Try spreading things out over different classes and files. Maks sure each class has only one purpose, instead of 1 class that manages a whole lot of different tasks.
That sounds like a sensible enough structure to me, what would really benefit you though is learning to use the tools you have available — whatever editor you're using it will have a search function, you can use that to quickly find what you're looking for.
Some editors will also include bookmarks too, and most offer a way to move back and forward through recent positions in the file.
Seen this sort of things started, never seen it kept on under the pressure to turn out code though.
Basically my rule of thumb is, if I feel the need to do this, break the code file up.
I've occasionally found myself in situations where I have to type out redundant code... where only one variable or two will change in each block of code. Usually I'll copy and paste this block and make the necessary changes on each block of code... but is there a better way to handle this?
Heavy use of cut and paste usually means there's something not quite right in the design of the code. Think about how you could refactor such as breaking out the cut/paste functionality into commonly called methods.
Yes. There is always a better way to do it than copy-and-paste. You should always get a little uneasy (kind of like you feel when you're about to give a speech in front of a huge crowd) when you're about to hit "Ctrl-V."
In almost any introductory class you're likely to be using a language that has functions, methods, or sub procedures. (What they're called and what they do depends on the language in question). Any variable that changes needs to be a parameter to that function/method/subprocedure.
When you do that (and the method/function/sub is accessible) you can replace the HUGE chunks of code with a single call to your new m-f-s.
There are a lot of other ways to do this, but when you're just getting started this is probably the way to go.
you have a lot of approaches to this situation. I don't know if you're working with OO or structured programming but you can build methods or functions and give them cohesion and unique responsibilities. I think it's an easy way of thinking...
In the OO paradigm we use some therms on how to avoid this situation: cohesion and low decoupling (you could search for them over the Internet). If you can apply both of them in your code, it will be easier to read and maintain.
That's all
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For those of you in the Visual Studio environment, how do you feel about wrapping any of your code in #regions? (or if any other IDE has something similar...)
9 out of 10 times, code folding means that you have failed to use the SoC principle for what its worth.
I more or less feel the same thing about partial classes. If you have a piece of code you think is too big you need to chop it up in manageable (and reusable) parts, not hide or split it up.It will bite you the next time someone needs to change it, and cannot see the logic hidden in a 250 line monster of a method.
Whenever you can, pull some code out of the main class, and into a helper or factory class.
foreach (var item in Items)
{
//.. 100 lines of validation and data logic..
}
is not as readable as
foreach (var item in Items)
{
if (ValidatorClass.Validate(item))
RepositoryClass.Update(item);
}
My $0.02 anyways.
This was talked about on Coding Horror.
My personal belief is that is that they are useful, but like anything in excess can be too much.
I use it to order my code blocks into:
Enumerations
Declarations
Constructors
Methods
Event Handlers
Properties
Sometimes you might find yourself working on a team where #regions are encouraged or required. If you're like me and you can't stand messing around with folded code you can turn off outlining for C#:
Options -> Text Editor -> C# -> Advanced Tab
Uncheck "Enter outlining mode when files open"
I use #Region to hide ugly and useless automatically generated code, which really belongs in the automatically generated part of the partial class. But, when working with old projects or upgraded projects, you don't always have that luxury.
As for other types of folding, I fold Functions all the time. If you name the function well, you will never have to look inside unless you're testing something or (re-)writing it.
While I understand the problem that Jeff, et. al. have with regions, what I don't understand is why hitting CTRL+M,CTRL+L to expand all regions in a file is so difficult to deal with.
I use Textmate (Mac only) which has Code folding and I find it really useful for folding functions, I know what my "getGet" function does, I don't need it taking up 10 lines of oh so valuable screen space.
I never use it to hide a for loop, if statement or similar unless showing the code to someone else where I will hide code they have seen to avoid showing the same code twice.
I prefer partial classes as opposed to regions.
Extensive use of regions by others also give me the impression that someone, somewhere, is violating the Single Responsibility Principle and is trying to do too many things with one object.
#Tom
Partial classes are provided so that you can separate tool auto-generated code from any customisations you may need to make after the code gen has done its bit. This means your code stays intact after you re-run the codegen and doesn't get overwritten. This is a good thing.
I'm not a fan of partial classes - I try to develop my classes such that each class has a very clear, single issue for which it's responsible. To that end, I don't believe that something with a clear responsibility should be split across multiple files. That's why I don't like partial classes.
With that said, I'm on the fence about regions. For the most part, I don't use them; however, I work with code every day that includes regions - some people go really heavy on them (folding up private methods into a region and then each method folded into its own region), and some people go light on them (folding up enums, folding up attributes, etc). My general rule of thumb, as of now, is that I only put code in regions if (a) the data is likely to remain static or will not be touched very often (like enums), or (b) if there are methods that are implemented out of necessity because of subclassing or abstract method implementation, but, again, won't be touched very often.
Regions must never be used inside methods. They may be used to group methods but this must be handled with extreme caution so that the reader of the code does not go insane. There is no point in folding methods by their modifiers. But sometimes folding may increase readability. For e.g. grouping some methods that you use for working around some issues when using an external library and you won't want to visit too often may be helpful. But the coder must always seek for solutions like wrapping the library with appropriate classes in this particular example. When all else fails, use folding for improving readibility.
This is just one of those silly discussions that lead to nowhere. If you like regions, use them. If you don't, configure your editor to turn them off. There, everybody is happy.
I generally find that when dealing with code like Events in C# where there's about 10 lines of code that are actually just part of an event declaration (the EventArgs class the delegate declaration and the event declaration) Putting a region around them and then folding them out of the way makes it a little more readable.
Region folding would be fine if I didn't have to manually maintain region groupings based on features of my code that are intrinsic to the language. For example, the compiler already knows it's a constructor. The IDE's code model already knows it's a constructor. But if I want to see a view of the code where the constructors are grouped together, for some reason I have to restate the fact that these things are constructors, by physically placing them together and then putting a group around them. The same goes for any other way of slicing up a class/struct/interface. What if I change my mind and want to see the public/protected/private stuff separated out into groups first, and then grouped by member kind?
Using regions to mark out public properties (for example) is as bad as entering a redundant comment that adds nothing to what is already discernible from the code itself.
Anyway, to avoid having to use regions for that purpose, I wrote a free, open source Visual Studio 2008 IDE add-in called Ora. It provides a grouped view automatically, making it far less necessary to maintain physical grouping or to use regions. You may find it useful.
I think that it's a useful tool, when used properly. In many cases, I feel that methods and enumerations and other things that are often folded should be little black boxes. Unless you must look at them for some reason, their contents don't matter and should be as hidden as possible. However, I never fold private methods, comments, or inner classes. Methods and enums are really the only things I fold.
My approach is similar to a few others here, using regions to organize code blocks into constructors, properties, events, etc.
There's an excellent set of VS.NET macros by Roland Weigelt available from his blog entry, Better Keyboard Support for #region ... #endregion. I've been using these for years, mapping ctrl+. to collapse the current region and ctrl++ to expand it. Find that it works a lot better that the default VS.NET functionality which folds/unfolds everything.
I personally use #Regions all the time. I find that it helps me to keep things like properties, declarations, etc separated from each other.
This is probably a good answer, too!
Coding Horror
Edit: Dang, Pat beat me to this!
The Coding Horror article actual got me thinking about this as well.
Generally, I large classes I will put a region around the member variables, constants, and properties to reduce the amount of text I have to scroll through and leave everything else outside of a region. On forms I will generally group things into "member variables, constants, and properties", form functions, and event handlers. Once again, this is more so I don't have to scroll through a lot of text when I just want to review some event handlers.
I prefer #regions myself, but an old coworker couldn't stand to have things hidden. I understood his point once I worked on a page with 7 #regions, at least 3 of which had been auto-generated and had the same name, but in general I think they're a useful way of splitting things up and keeping everything less cluttered.
I really don't have a problem with using #region to organize code. Personally, I'll usually setup different regions for things like properties, event handlers, and public/private methods.
Eclipse does some of this in Java (or PHP with plugins) on its own. Allows you to fold functions and such. I tend to like it. If I know what a function does and I am not working on it, I dont need to look at it.
Emacs has a folding minor mode, but I only fire it up occasionally. Mostly when I'm working on some monstrosity inherited from another physicist who evidently had less instruction or took less care about his/her coding practices.
Using regions (or otherwise folding code) should have nothing to do with code smells (or hiding them) or any other idea of hiding code you don't want people to "easily" see.
Regions and code folding is really all about providing a way to easily group sections of code that can be collapsed/folded/hidden to minimize the amount of extraneous "noise" around what you are currently working on. If you set things up correctly (meaning actually name your regions something useful, like the name of the method contained) then you can collapse everything except for the function you are currently editing and still maintain some level of context without having to actually see the other code lines.
There probably should be some best practice type guidelines around these ideas, but I use regions extensively to provide a standard structure to my code files (I group events, class-wide fields, private properties/methods, public properties/methods). Each method or property also has a region, where the region name is the method/property name. If I have a bunch of overloaded methods, the region name is the full signature and then that entire group is wrapped in a region that is just the function name.
I personally hate regions. The only code that should be in regions in my opinion is generated code.
When I open file I always start with Ctrl+M+O. This folds to method level. When you have regions you see nothing but region names.
Before checking in I group methods/fields logically so that it looks ok after Ctrl+M+O.
If you need regions you have to much lines in your class. I also find that this is very common.
region ThisLooksLikeWellOrganizedCodeBecauseIUseRegions
// total garbage, no structure here
endregion
Enumerations
Properties
.ctors
Methods
Event Handlers
That's all I use regions for. I had no idea you could use them inside of methods.
Sounds like a terrible idea :)