Which is the better name for a method that returns a boolean?
IsSupportContentType
or
CanSupportContentType
3 Answers
Is vs. Can
According to the Microsoft naming convention recommendations, both "Is" and "Can" are OK (and so is "Has") as a prefix for a Boolean.
In plain English, "Is" would be used to identify something about the type itself, not what it can do. For example, IsFixed, IsDerivedFrom, IsNullable can all be found in CLR types and methods. In all of these cases, "Is" is followed by an adjective.
Meanwhile, "can" more clearly indicates a capability, e.g. CanEdit, CanRead, CanSeek. In each of these cases, can is followed by a verb.
Since "Support" is a verb, I think in your case CanSupportContentType is better.
Shorter alternative
On the other hand, the conventions say the prefix is optional. What's more, it's kind of cheesy to include the argument type in the method name, since a developer can see the type of the argument in intellisense. So you could just name your method Supports and define it like this:
public bool Supports(System.Net.Mime.ContentType contentType)
...which is shorter and still clearly communicates the purpose. You'd call it like this:
ContentType contentType = new ContentType("text/plain");
var someClass = new MediatorsClass();
bool ok = someClass.Supports(contentType);
Or as a compromise maybe this is best:
public bool CanSupport(System.Net.Mime.ContentType contentType)
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61It's nice when it reads well:
if ( someClass.Supports(contentType) )May 9, 2017 at 23:28 -
6
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9A method called "CanSupports" initiallty mades me wonder who spent time to make the software able to support cans (as in tin cans). Just "Supports" is the better option, no doubt!– T. SarMay 10, 2017 at 13:10
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7Sometimes developers can't tell when something "sounds weird," e.g. if English is not their first language.– John WuMay 10, 2017 at 18:28
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10Sometimes a shorter version is worse. E.g. in the C++ Standard library we have
std::vector::empty(). From its name only, does it empty the vector? Or does it return whether the vector is empty? Actually the latter, since the former task is done bystd::vector::clear(). But you must in general read the docs to be sure. As an opposite example, Qt'sQVectoris easier to understand in this regard, since its method of checking for emptiness isQVector::isEmpty().– RuslanMay 10, 2017 at 21:08
It's worth mentioning that the "should" prefix can also be used. According to Apple's guideline, not just "can" and "should", modal verbs in general can be used to name functions that return boolean. I can't see many use of "will" but "should" is nice for advice-inquiring hooks, as seen in reactjs:
shouldComponentUpdate: (newProps: any) => boolean
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27should is imho pretty poor naming, "well, it should close the document, but i'm actually not quite sure"– LovisMay 10, 2017 at 13:13
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4@lovis: I think Harry's comment is very valid. For example, I could delegate some database-related actions through a plugin layer, each plugin has a "ShouldCloseConnection" method which informs the framework that some cleanup should be performed. Just an example, but "should" is definitely a valid prefix.– gregMay 10, 2017 at 15:30
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1
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1@Lovis We generally use
is...but useshould...in some function argument names, places where the boolean indicates what the function is supposed to change things to. If a function can optionally close a document, calling the parameter controlling thatisClosedwould be accurate (it’s not closed yet) and so we would useshouldCloseto indicate that this is what the function is supposed to do. (Arbitrary example; we wouldn’t likely have a function like this, particularly since closing a document should be weighty enough to have a dedicated call.)– KRyanMay 10, 2017 at 18:36 -
1More seriously, how would you prefix a boolean for some element that has to show, to be displayed: myButton.shouldShow, anything else?– lapinMay 2, 2019 at 7:54
For the people against the use of "should" prefix for boolean arguments, here is my fresh last one used for an optional argument name (but I need to agree that I can't even remember last time I've used this prefix):
MethodNameToUpdateDataList(..., bool shouldDeactivateMissingIds = false) {}
Neither "is", "can" nor "will" prefix seems ok there... What do you think?
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Another one: shouldAutoAllocateMovements. Whaou, none for years and two used in the same day :D– IslemNov 12, 2021 at 14:28
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Know I think that I understand, actually, most of the time, even with quite good coding practice when we use a boolean argument named without a standard prefix, we usually use directly the verb. Also meaning that, everytime we see a case like this, that means that it could have been prefixed with "should".– IslemNov 12, 2021 at 23:17
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What exactly does "should" indicate? Is there some logic behind this method that sometimes deactivates IDs? If not, the should prefix is redundant and misleading.– kiwironNov 22, 2021 at 6:40
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@kiwiron: The anwser to your question: "Is there some logic behind this method that sometimes deactivate" --> is Yes ! That is why, the caller of this method has to decide (himself) or let default but, he can force to true in some cases. The method itself doesn't know yet when to do it or not, but the method still handle both logics. The caller is the one knowing when here.– IslemFeb 9 at 13:16
IsSupportedContentTypeto be grammatically correct. (unless "support content type" acts as a noun, which seems unlikely)supportsContentType? The following is entirely readable:if (abc.supportsContentType("text/html")). "can support" implies that there are further conditions to support the content-type.