C# – Is nesting types considered bad practice

cdesignreadability

As noted by the title, is nesting types (e.g. enumerated types or structures in a class) considered bad practice or not? When you run Code Analysis in Visual Studio it returns the following message which implies it is:

Warning 34 CA1034 : Microsoft.Design :
Do not nest type
'ClassName.StructueName'.
Alternatively, change its
accessibility so that it is not
externally visible.

However, when I follow the recommendation of the Code Analysis I find that there tend to be a lot of structures and enumerated types floating around in the application that might only apply to a single class or would only be used with that class. As such, would it be appropriate to nest the type sin that case, or is there a better way of doing it?

Best Answer

Nested types are not bad. The warning you are receiving is not suggesting you never have a nested type. It is simply indicating that your nested type should use an appropriate access modifier and code location.

If the nested type is truly only used inside the containing class (i.e. it is an internal data container or status indicator), then set its access modifier to private.

If the nested type is part of one or more method signatures, then it is not in fact local to the containing class. It represents a message being passed to or from instances of the containing class. In this case, it is arguably better to move the nested type out of the containing class, and give it a more open access modifier such as internal or public.

In short, the warning appears to be recommending that you make local types private, and shared types should stand alone.

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Java Readability – Why Are Nested Loops Considered Bad Practice?

Nested loops are fine as long as they describe the correct algorithm.

Nested loops have performance considerations (see @Travis-Pesetto's answer), but sometimes it's exactly the correct algorithm, e.g. when you need to access every value in a matrix.

Labeling loops in Java allows to prematurely break out of several nested loops when other ways to do this would be cumbersome. E.g. some game might have a piece of code like this:

Player chosen_one = null;
...
outer: // this is a label
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      }
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}

While code like the example above may sometimes be the optimal way to express a certain algorithm, it is usually better to break this code into smaller functions, and probably use return instead of break. So a break with a label is a faint code smell; pay extra attention when you see it.

Java JPA – Is ElementCollection Considered Bad Practice?

I had a simple case with I first solved with an enum that was stored inside a ElementCollection. It would suffice in your situation because you would most likely just query the whole collection and then you can do your operations on the Set. If you want on the other hand to have your choices to be more extensible you should create another Entity for DownloadFilePreferences.

ome best practices suggest to never have a class without a primary key

Just because you didn't declare a primary it doesn't mean that your JPA implementation doesn't create an id on the mapping table.

Best Answer

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