If a method takes a class/struct as an input parameter, what is the best way to name it?
Example:
class Person{}
class Address{}
class Utility{
//name **style 1** - use method overloading
public void Save(Person p){}
public void Save(Address a){}
*//name **style 2** - use unique names that define what they are doing
//or public void SavePerson(Person p){}
//and public void SaveAddress(Address a){}*
}
I personally like style 1 (Use the languages features - in this case overloading).
If you like style 1, can you point me to any "official" documentation, that states this to be a standard?
I would say your challenge is not in the field of method naming, but rather type design. A type that is responsible for saving both Person objects and Address objects seems like a type with more than one responsibility. Such a type will tend to grow and grow and grow and will eventually get hard to maintain. If you instead create more specialized types, method naming may automatically become a simpler task.
If you would still want to collect these methods in the same type, it's mostly a matter of style. One thing to perhaps think about is whether this type may be consumed by code written in another language, and that does not support method overloading. In such cases the longer names is the way to go. Otherwise just stick to what feels best (or whatever is the ruling convention at your workplace).
It is a matter of style.
If you don't like long method names, go with 1.
If you don't like long overload lists, go with 2.
The important bit is to keep consistent, so do not mix the two styles in one project.
If you are seeing that you have many such methods, you may need to rethink your design - perhaps a solution involving inheritance would be more appropriate.
Distinct names avoid entirely any problems associated with method overloading. For example:
Ambiguity is avoided if an argument's type matches more than one of the candidates.
In C++, overloaded methods can hide those of the same name in a superclass.
In Java, type erasure prevents overloaded methods differing only by type parameterization.
It would also be worthwhile to ask whether polymorphism could be used instead of overloading.
Related
I read through the TypeScript Coding guidelines
And I found this statement rather puzzling:
Do not use "I" as a prefix for interface names
I mean something like this wouldn't make a lot of sense without the "I" prefix
class Engine implements IEngine
Am I missing something obvious?
Another thing I didn't quite understand was this:
Classes
For consistency, do not use classes in the core compiler pipeline. Use
function closures instead.
Does that state that I shouldn't use classes at all?
Hope someone can clear it up for me :)
When a team/company ships a framework/compiler/tool-set they already have some experience, set of best practices. They share it as guidelines. Guidelines are recommendations. If you don't like any you can disregard them.
Compiler still will compile your code.
Though when in Rome...
This is my vision why TypeScript team recommends not I-prefixing interfaces.
Reason #1 The times of the Hungarian notation have passed
Main argument from I-prefix-for-interface supporters is that prefixing is helpful for immediately grokking (peeking) whether type is an interface. Statement that prefix is helpful for immediately grokking (peeking) is an appeal to Hungarian notation. I prefix for interface name, C for class, A for abstract class, s for string variable, c for const variable, i for integer variable. I agree that such name decoration can provide you type information without hovering mouse over identifier or navigating to type definition via a hot-key. This tiny benefit is outweighed by Hungarian notation disadvantages and other reasons mentioned below. Hungarian notation is not used in contemporary frameworks. C# has I prefix (and this the only prefix in C#) for interfaces due to historical reasons (COM). In retrospect one of .NET architects (Brad Abrams) thinks it would have been better not using I prefix. TypeScript is COM-legacy-free thereby it has no I-prefix-for-interface rule.
Reason #2 I-prefix violates encapsulation principle
Let's assume you get some black-box. You get some type reference that allows you to interact with that box. You should not care if it is an interface or a class. You just use its interface part. Demanding to know what is it (interface, specific implementation or abstract class) is a violation of encapsulation.
Example: let's assume you need to fix API Design Myth: Interface as Contract in your code e.g. delete ICar interface and use Car base-class instead. Then you need to perform such replacement in all consumers. I-prefix leads to implicit dependency of consumers on black-box implementation details.
Reason #3 Protection from bad naming
Developers are lazy to think properly about names. Naming is one of the Two Hard Things in Computer Science. When a developer needs to extract an interface it is easy to just add the letter I to the class name and you get an interface name. Disallowing I prefix for interfaces forces developers to strain their brains to choose appropriate names for interfaces. Chosen names should be different not only in prefix but emphasize intent difference.
Abstraction case: you should not not define an ICar interface and an associated Car class. Car is an abstraction and it should be the one used for the contract. Implementations should have descriptive, distinctive names e.g. SportsCar, SuvCar, HollowCar.
Good example: WpfeServerAutosuggestManager implements AutosuggestManager, FileBasedAutosuggestManager implements AutosuggestManager.
Bad example: AutosuggestManager implements IAutosuggestManager.
Reason #4 Properly chosen names vaccinate you against API Design Myth: Interface as Contract.
In my practice, I met a lot of people that thoughtlessly duplicated interface part of a class in a separate interface having Car implements ICar naming scheme. Duplicating interface part of a class in separate interface type does not magically convert it into abstraction. You will still get concrete implementation but with duplicated interface part. If your abstraction is not so good, duplicating interface part will not improve it anyhow. Extracting abstraction is hard work.
NOTE: In TS you don't need separate interface for mocking classes or overloading functionality.
Instead of creating a separate interface that describes public members of a class you can use TypeScript utility types. E.g. Required<T> constructs a type consisting of all public members of type T.
export class SecurityPrincipalStub implements Required<SecurityPrincipal> {
public isFeatureEnabled(entitlement: Entitlement): boolean {
return true;
}
public isWidgetEnabled(kind: string): boolean {
return true;
}
public areAdminToolsEnabled(): boolean {
return true;
}
}
If you want to construct a type excluding some public members then you can use combination of Omit and Exclude.
Clarification regarding the link that you reference:
This is the documentation about the style of the code for TypeScript, and not a style guideline for how to implement your project.
If using the I prefix makes sense to you and your team, use it (I do).
If not, maybe the Java style of SomeThing (interface) with SomeThingImpl (implementation) then by all means use that.
I find #stanislav-berkov's a pretty good answer to the OP's question. I would only share my 2 cents adding that, in the end it is up to your Team/Department/Company/Whatever to get to a common understanding and set its own rules/guidelines to follow across.
Sticking to standards and/or conventions, whenever possible and desirable, is a good practice and it keeps things easier to understand. On the other side, I do like to think we are still free to choose the way how we write our code.
Thinking a bit on the emotional side of it, the way we write code, or our coding style, reflects our personality and in some cases even our mood. This is what keeps us humans and not just coding machines following rules. I believe coding can be a craft not just an industrialized process.
I personally quite like the idea of turning a noun into an adjective by adding the -able suffix. It sounds very impropper, but I love it!
interface Walletable {
inPocket:boolean
cash:number
}
export class Wallet implements Walletable {
//...
}
}
The guidelines that are suggested in the Typescript documentation aren't for the people who use typescript but rather for the people who are contributing to the typescript project. If you read the details at the begging of the page it clearly defines who should use that guideline. Here is a link to the guidelines.
Typescript guidelines
In conclusion as a developer you can name you interfaces the way you see fit.
I'm trying out this pattern similar to other answers, but exporting a function that instantiates the concrete class as the interface type, like this:
export interface Engine {
rpm: number;
}
class EngineImpl implements Engine {
constructor() {
this.rpm = 0;
}
}
export const createEngine = (): Engine => new EngineImpl();
In this case the concrete implementation is never exported.
I do like to add a Props suffix.
interface FormProps {
some: string;
}
const Form:VFC<FormProps> = (props) => {
...
}
The type being an interface is an implementation detail. Implementation details should be hidden in API:s. That is why you should avoid I.
You should avoid both prefix and suffix. These are both wrong:
ICar
CarInterface
What you should do is to make a pretty name visible in the API and have a the implemtation detail hidden in the implementation. That is why I propose:
Car - An interface that is exposed in the API.
CarImpl - An implementation of that API, that is hidden from the consumer.
In the smell Data Class as Martin Fowler described in Refactoring, he suggests if I have a collection field in my class I should encapsulate it.
The pattern Encapsulate Collection(208) says we should add following methods:
get_unmodified_collection
add_item
remove_item
and remove these:
get_collection
set_collection
To make sure any changes on this collection need go through the class.
Should I refactor every class which has a collection field with this pattern? Or it depends on some other reasons like frequency of usage?
I use C++ in my project now.
Any suggestion would be helpful. Thanks.
These are well formulated questions and my answer is:
Should I refactor every class which has a collection field with this
pattern?
No, you should not refactor every class which has a collection field. Every fundamentalism is a way to hell. Use common sense and do not make your design too good, just good enough.
Or it depends on some other reasons like frequency of usage?
The second question comes from a common mistake. The reason why we refactor or use design pattern is not primarily the frequency of use. We do it to make the code more clear, more maintainable, more expandable, more understandable, sometimes (but not always!) more effective. Everything which adds to these goals is good. Everything which does not, is bad.
You might have expected a yes/no answer, but such one is not possible here. As said, use your common sense and measure your solution from the above mentioned viewpoints.
I generally like the idea of encapsulating collections. Also encapsulating plain Strings into named business classes. I do it almost always when the classes are meaningful in the business domain.
I would always prefer
public class People {
private final Collection<Man> people;
... // useful methods
}
over the plain Collection<Man> when Man is a business class (a domain object). Or I would sometimes do it in this way:
public class People implements Collection<Man> {
private final Collection<Man> people;
... // delegate methods, such as
#Override
public int size() {
return people.size();
}
#Override
public Man get(int index) {
// Here might also be some manipulation with the returned data etc.
return people.get(index);
}
#Override
public boolean add(Man man) {
// Decoration - added some validation
if (/* man does not match some criteria */) {
return false;
}
return people.add(man);
}
... // useful methods
}
Or similarly I prefer
public class StreetAddress {
private final String value;
public String getTextValue() { return value; }
...
// later I may add more business logic, such as parsing the street address
// to street name and house number etc.
}
over just using plain String streetAddress - thus I keep the door opened to any future change of the underlying logic and to adding any useful methods.
However, I try not to overkill my design when it is not needed so I am as well as happy with plain collections and plain Strings when it is more suited.
I think it depends on the language you are developing with. Since there are already interfaces that do just that C# and Java for example. In C# we have ICollection, IEnumerable, IList. In Java Collection, List, etc.
If your language doesn't have an interface to refer to a collection regarless of their inner implementation and you require to have your own abstraction of that class, then it's probably a good idea to do so. And yes, you should not let the collection to be modified directly since that completely defeats the purpose.
It would really help if you tell us which language are you developing with. Granted, it is kind of a language-agnostic question, but people knowledgeable in that language might recommend you the best practices in it and if there's already a way to achieve what you need.
The motivation behind Encapsulate Collection is to reduce the coupling of the collection's owning class to its clients.
Every refactoring tries to improve maintainability of the code, so future changes are easier. In this case changing the collection class from vector to list for example, changes all the clients' uses of the class. If you encapsulate this with this refactoring you can change the collection without changes to clients. This follows on of SOLID principles, the dependency inversion principle: Depend upon Abstractions. Do not depend upon concretions.
You have to decide for your own code base, whether this is relevant for you, meaning that your code base is still being changed and has to be maintained (then yes, do it for every class) or not (then no, leave the code be).
I've been reading on refactoring and replacing conditional statements with polymorphism. The trouble I have is that it only seems to make sense to me when you have a more complex case where, without polymorphism, you would have to repeat the same switch statements or if-elses many times. I don't see how it makes sense if you're only doing it once - you have to have that conditional somewhere, right?
As an example, I recently wrote the following class, which is responsible for reading a XML file and converting its data into the program's objects. There are 2 possible formats for the file that we are supporting, so I simply wrote a method in the class for handling each one, and used a case-switch to determine which one to use:
public class ComponentXmlReader
{
public IEnumerable<UserComponent> ImportComponentsFromXml(string path)
{
var xmlFile = XElement.Load(path);
switch (xmlFile.Name.LocalName)
{
case "CaseDefinition":
return ImportComponentsFromA(xmlFile);
case "Root":
return ImportComponentsFromB(xmlFile);
}
}
private IEnumerable<UserComponent> ImportComponentsFromA(XContainer file)
{
//do stuff
}
private IEnumerable<UserComponent> ImportComponentsFromB(XContainer file)
{
//do stuff
}
}
As far as I can tell, I could write a class hierarchy for this to do the parsing, but I don't see the advantage here - I'd still have to use a case-switch to determine which class to instantiate. It looks to me like it would be extra complexity for no benefit. If I was going to keep these classes around and do more things with them that depended on the file type, then it would eliminate doing the same switch in multiple places, but this is single-use. Is this right, or is there some reason or technique I'm not seeing that makes it a good idea to use a polymorphic class hierarchy to do this?
If you had, say, an abstract ComponentImporter class, with concrete subclasses FromA and FromB, you could instantiate one of each, and put it in a Map. Then you could call componentImporterMap.get(xmlFile.Name.LocalName).importComponents() and avoid the switch.
As with all design choices, context is key. In this case, you have what seems to be a fairly simple class handling two very similar tasks. If the two Import methods contained very little duplicate code, then including them in a single class is perhaps the best choice since, as you say, it reduces complexity.
However, it's possible you'll use this class in the future, and even add new types of imports. In that case, the class would be more reusable if it was polymorphic.
Additionally, since these methods sound very similar, you're likely to have a bunch of duplicate code, which you could keep in a base class and only put import-specific code in the child classes.
Plus, as Carl mentions, there are numbers of ways to implement this logic without using a case statement.
The good style (Clean Code book) says that a method's name should describe what the method does. So for example if I have a method that verifies an address, stores it in a database, and sends an email, should the name be something such as verifyAddressAndStoreToDatabaseAndSendEmail(address);
or
verifyAddress_StoreToDatabase_SendEmail(address);
although I can divide that functionality in 3 methods, I'll still need a method to call these 3 methods. So a large method name is inevitable.
Having And named methods certainly describes what the method does, but IMO it's not very readable as names can be very very large. How would you solve it?
EDIT: Maybe I could use fluent style to decompose the method name such as:
verifyAddress(address).storeToDatabase().sendEmail();
but I need a way to ensure the order of invocation. Maybe by using the state pattern, but this causes the code to grow.
How I approach this is to make the 3 smaller methods as you mentioned and then in the higher method that calls the 3 smaller ones, I name it after the "why" I need to do those three things.
Try to define why you need to do those steps and use that as the basis of the method name.
A single method should not do 3 things. Thus divide the work into 3 methods:
verifyAddress
storeAddress
sendEmail
I'm following up on my previous comment, but I've got more here than would fit reasonably in a comment so I'm answering.
The details of the method belong in the documentation not in the name of the method (in my opinion). Think of it this way... By putting SendEmail in the name of the method, you're committing implementation details to the method name. What if a decision is made down the road to send notification via SMS or twitter or something else instead of email? Do you change the name of the method and break your API, or do you have a method name that misleads the consumers of the API? Something to consider.
If you insist on keeping the functionality of the method in its name, I'd urge you to find something more generic. Perhaps something along the lines of VerifySaveAndNotify(Address address). That way, the method name tells you what it's doing without specifying how it does it. The parameter of type Address let's you know what is being verified and saved. All of that works together to make your method name informative, flexible, and terse.
EDIT: Maybe I could use fluent style to decompose the method name such as:
verifyAddress(address).storeToDatabase().sendEmail();
but I need a way to ensure the order of invocation. Maybe by using the state pattern, but this causes the code to grow.
To ensure ordering of commands in a fluent style, each result would be an object that exposes only the functionality required by the next step. For example:
public class Verifier
{
public DataStorer VerifyAddress(string address)
{
...
return new DataStorer(address);
}
}
public class DataStorer
{
public Emailer StoreToDataBase()
{
...
return new Emailer(...);
}
}
public class Emailer
{
public void SendEmail()
{
...
}
}
This is handy if you need to create a very granular design and want to optimise your classes for reuseability, but is likely to be design overkill under most circumstances. Better probably as others have said to choose a name that represents what the whole process is supposed to represent. You could simply call it "StoreAndEmail", making an assumption that verification is something you do routinely before committing data to any destination. The alternative if you don't mind names being long is to simply describe it in full and accept that a long name is necessary. In the end, it really doesn't cost you anything, but can certainly make you code more specific in its intent.
Starting with this code:
new Person("ET").WithAge(88)
How can it be refactored to:
new Person("ET", 88)
What sequence of refactorings needs to be performed to complete the transformation?
Why? Because there could be hundreds of these, and I wouldn't want to introduce errors by doing it manually.
Would you say a drawback with fluent interfaces is they can't easily be refactored?
NOTE: I want to do this automatically without hand typing the code.
Perhaps the simplest way to refactor this is to change the name "WithAge" to "InitAge", make InitAge private, then call it from your constructor instead. Then update all references of new Person(string).WithAge(int) to use the new constructor.
If WithAge is a one-liner, you can just move the code to your new constructor instead, and do away with InitAge altogether, unless having the additional method provides extra readability.
Having good unit tests will isolate where errors are introduced, if they are.
Assuming that WithAge is a method on Person that returns a Person, what about something like
Person(string name, int age)
{
this.name = name;
this.WithAge(age);
}
Or more generalized:
Person(SomeType originalParameter, FluentParamType fluentParameter)
{
//Original constructor stuff
this.FluentMethod(fluentParameter);
}
And then as make the FluentMethod private if you don't want it, or keep it public if you want to allow both ways.
If this is C# (ideally you would tag the question with the language), the Person class needs this constructor:
public Person(string name, int age)
: this(name) { WithAge(age); }
To then change all client code to call this new constructor where appropriate, you would need to find all occurrences of the pattern:
new Person(x1).WithAge(x2)
where x1 and x2 are expressions, and replace them with:
new Person(x1, x2)
If there are other modifier methods aside from WithAge, it might get more complicated. For example:
new Person(x1).WithHair(x2).WithAge(x3)
Perhaps you'd want that to become:
new Person(x1, x3).WithHair(x2)
It all depends on whether you have an IDE that lets you define language-aware search/replace patterns like that. You can get a long way to the solution with simple textual search and replace, combined with a macro that replays a sequence of key presses.
Would you say a drawback with fluent
interfaces is they can't easily be
refactored?
Not especially - it's more that refactoring features in IDEs are either designed flexibly enough to let you creatively invent new refactorings, or else they are hard-coded for certain common cases. I'd prefer the common cases to be defined as examples that I could mutate to invent new ones.
I don't have any practical experience with that sort of thing, but if I was in your situation the place I'd go looking would be custom Eclipse refactorings (or the equivalent in Refactor! Pro for .Net if that's what you're using).
Basically what you want is a match and replace, except that your regular expressions should match abstract syntax trees rather than plain text. That's what automated refactorings are.
One risk of this refactoring is that the target version is less precise than the original. Consider:
class Person {
public Person(String name, int age);
public Person(String name, int numberOfChildren);
}
There is no way to tell which of these constructors the chained call to Person.WithAge should be replaced with.
So, automated support for this would have to check for such ambiguities before allowing you to proceed. If there is already a constructor with the target parameters, abort the refactoring.
Other than that it seems pretty straightforward. Give the new constructor the following content:
public Person(String name, int age) {
this(name);
withAge(age);
}
Then you can safely replace the original call with the new.
(There is a subtle additional risk, in that calling withAge within the constructor, i.e. on a partially constructed object, isn't quite the same as calling it after the constructor. The difference matters if you have an inheritance chain and if withAge does something non-trivial. But then that's what your unit tests are for...)
Write unit tests for the old code.
Refactor until the tests pass again.