I am getting rubocop error 'Class definition is too long. [236/100]'.
My class looks like below:
class SomeClassName
include HelperModule
attr_accessor :aaa, :bbb, :ccc
.... methods .....
end
What might go wrong?
The rubocop docs ClassLength says "length of a class exceeds some maximum value".
What does it mean?
Yes, this is because the overall lines are considered to be too many by rubucop. I agree classes shouldn't get too long but think that should ultimately be determined by: does the class have a single responsibility, are the methods concise enough, are there methods that could be shared via module, etc... The number/alert is a great warning though. If things in the class look OK, you can add # rubocop:disable ClassLength immediately above the class definition.
This likely means that your class definition takes more than 100 lines of code.
(There's lots of good info here already, but I came to this answer looking for the syntax for specifying the max lines per class in Rubocop, and I figure others might come here for that as well.)
In .rubocop.yml
# Allow classes longer than 100 lines of code
ClassLength:
Max: 250 # or whatever ends up being appropriate
General answer
Do I need to disable this cop if I want my class to be longer than 100 here or need to configure the maximum length. What would you suggest?
I use rubocop with this workflow, assuming I encounter a pre-existing code base with loads of warnings:
Run rubocop --auto-gen-config to create a "TODO" file. Include that file in your primary rubocop configuration file. See their documentation for details. In your example, it would generate a configuration that allows long classes (at least 236 lines, or more if you have larger classes).
Now, if you run rubocop, it will ignore all offences that you put in your TODO file - i.e., everything will looke fine now. Only if you introduce more errors/warnings (like a class with 237 lines) will it fire up again. So, at this point, rubocop will not do anything for you except prevent you to make it worse.
Once in a while, when I got some time to kill, I pick a rule from the TODO file and work on it. There are three possibilities:
Remove the rule from the TODO file. This will restore the original behaviour of rubocop.
Relax the number associated with it. Say, the class length is limited to 250 right now; I would like to set it to (say) 100 lines, but I know that I do not have time to refactor many classes right now. So I set it to 240. This will trigger all classes that are between 240 and 250 lines; likely only a few that I can handle easily. I fix them and move on. Another day, I maybe return to it and go from 240 to 230 etc.
Sometimes I decide that I do not bother about a particular warning. Then I move the configuration from the TODO file to the proper .rubocop file, allowing it permanently.
So, there are no hard and fast rules about all of this. You are supposed to find your own values. Some things that rubocop objects to are totally fine with me since they are more down to coding style than correctness or whatever.
Specific answer
Do I need to disable this cop if I want my class to be longer than 100 here or need to configure the maximum length. What would you suggest?
I most certainly do have a maximum amount of lines configured for my class files (as well as for methods). The length of a unit of code (be it a class or a method) is a very simple yet effective "code smell" that points to grown code and candidates for refactoring/splitting.
I have picked some numbers for me, and I stick with them. I.e., I don't constantly move them up or down to suit the particular code around, but if a piece of code grows "1 line too large", I take action. Most times my target is to split it roughly in half, which will, in the long run, lead to the minimum required effort.
If a class is very long, it usually breaks the "one responsibility per class" rule. It is usually beneficial to break it down into parts. Not just random subclasses, but actully OO-justifiable, patterned, constructs.
If a method is very long, it can sometimes point to OO measures to be taken (i.e., classes introduced or the method being split over existing classes; especially if the method consists of large if/else constructs or especially case statements), but more often it calls for simple old-fashioned refactoring into smaller (likely private) methods.
Have fun finding your favourite settings in rubocop, it's awesome.
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.
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Personally I can't stand region tags, but clearly they have wide spread appeal for organizing code, so I want to test the temperature of the water for other MS developer's take on this idea.
My personal feeling is that any sort of silly trick to simplify code only acts to encourage terrible coding behavior, like lack of cohesion, unclear intention and poor or incomplete coding standards.
One programmer told me that code regions helped encourage coding standards by making it clear where another programmer should put his or her contributions.
But, to be blunt, this sounds like a load of horse manure to me. If you have a standard, it is the programmer's job to understand what that standard is... you should't need to define it in every single class file.
And, nothing is more annoying than having all of your code collapsed when you open a file. I know that cntrl + M, L will open everything up, but then you have the hideous "hash region definition" open and closing lines to read.
They're just irritating.
My most stead fast coding philosophy is that all programmer should strive to create clear, concise and cohesive code. Region tags just serve to create noise and redundant intentions.
Region tags would be moot in a well thought out and intentioned class.
The only place they seem to make sense to me, is in automatically generated code, because you should never have to read that outside of personal curiosity.
I like regions, and use them all the time. I use them to group members of the same kind inside classes.
You already have the means to collapse methods, classes and namespaces in the editor. Regions give you an option to create another level that lets you arrange the code in a way that corresponds to what you think is important.
StyleCop doesn't like regions:
SA1124: DoNotUseRegions
Cause
The C# code contains a region.
Rule Description
A violation of this rule occurs whenever a region is placed anywhere within the code. In many editors, including Visual Studio, the region will appear collapsed by default, hiding the code within the region. It is generally a bad practice to hide code, as this can lead to bad decisions as the code is maintained over time.
How to Fix Violations
To fix a violation of this rule, remove the region from the code.
There is some discussion about whether or not this is a reasonable rule.
The consensus seems to be that some people like regions and some people don't - it is up to individual teams to decide. The most important thing is to use a consistent style throughout your project.
One place where regions might be acceptable is to group all the methods that implement a particular interface. It is worth noting that Visual Studio automatically adds a region if you use the code generation feature to provide method stubs for implementing an interface.
The only place they seem to make sense to me, is in automatically generated code, because you should never have to read that outside of personal curiosity.
The partial class feature is better for separating automatically generated code from manually generated code within the same class.
When working with automatically generated source, code can be added to the class without having to recreate the source file. Visual Studio uses this approach when it creates Windows Forms, Web service wrapper code, and so on. You can create code that uses these classes without having to modify the file created by Visual Studio.
I think that #region is perfectly fine. I've never used it myself, but if you have a large or complex class, it can help with finding what you're looking for. Imagine if you're implementing ID3D10Device1- that's over a hundred methods to implement. You want to just throw them all in one place?
I do use regions to organize bigger constructs in a class, ie. a Dependency Property with callback and methods getting called by this, eg. you have a DP that takes an IEnumerable<T>, and you want to use the weak event pattern to respond to INotifyCollectionChanged. This can take some code, and as I won't be touching it after coding it, I put it in a region.
However, if you resort to regions to structure your logic, this is severe code smell and that's what the StyleCop rule in Mark's post is pointing hat.
while I am programming I use regions a lot they help me keeping my code organised and be able to focus only on parts I care. I always add comments on the regions and what are they about .But when I am done I am always removing them. Its a handy tool, that's all.
IHMO, if you have #region section in a class, it means that you have two behaviors in your class and so you should split your class in two objects.
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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 :)