Software Engineering Stack Exchange
Software Engineering Stack Exchange

Questions tagged [trait]

19 questions
19
votes
1 answer

Why not make a language with mixin-only inheritance?

It seems that in all class-based or prototypal OOP languages, mixins are either an afterthought or a secondary feature. However, to me it looks like traditional inheritance is just a specific case of using a single mixin. I am assuming this is…
Den
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17
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2 answers

Should a trait refer to parent methods?

Is it a code smell if the methods in my trait refer to parent::methods or to methods that are assumed to be in the utilising class? A random (senseless) example trait foo { public function bar() { return parent::bar() . 'baz'; …
Kamafeather
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10
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2 answers

What's the difference between a Mixin and a Trait?

From what I can tell from Scala and Hack- Mixins: Can have state (ie. instance properties) Can only provide concrete methods Can have constructors, that are called in the same order that their classes were mixed in If A mixes in B and C, A…
bcherny
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10
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2 answers

Is there a way to document required properties in traits (PHP)?

I'm fairly new to using traits in PHP and am wondering if there is a way to ensure that a class including a trait has particular properties. I know that you can use something like the following to ensure the using class has particular…
Privateer
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10
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2 answers

Why can't the Scala compiler give pattern matching warning for nonsealed classes/traits?

If I use an unsealed trait or abstract class in Scala and then use pattern matching, I wonder, does the compiler not know at compile time for this particular patternmatch what possible implementations of this trait/class are available? So, if it…
valenterry
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8
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2 answers

Is it possible to mock and inject traits in PHPUnit?

I need to extend a third party class I cannot modify. The class's dependencies are for the most part injected through the constructor, making them easy to mock. However the class also uses methods from a trait that call global services directly,…
TravisCarden
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7
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1 answer

Comparision of modeling with inheritance vs idiomatic trait based composition

I recently I started learning Rust and Scala and what struck me was the lack of inheritance model that I'm used to in C++ and Java. Although I can model simple things with structs and traits in Rust, I want to see a more idiomatic way to model…
sadiq.ali
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7
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2 answers

Is trait composition an good practice?

So, I am now dealing with this relatively new codebase which uses, and sometimes feels like it abuses traits. Since I have been exposed to trait usage in a rather limited fashion, I was wondering whether the way they are using them makes sense. I…
memo
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7
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1 answer

Why are Scala's Either and Option types not interfaces/traits but classes?

I wanted to create a class CompileResult, that can be treated like an Either type but has some additional useful methods. It should be a CompileSuccess or a CompileFailure (which, too, has some extended functionality). However I can't do that…
valenterry
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6
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3 answers

How to track C++ class traits?

As a fan of regular types and value semantics, I'm keen on classes becoming more regular and being non-polymorphic. As a fan of non-throwing operations, I'm keen on operations being noexcept. I also appreciate confirmation of what special member…
Louis Langholtz
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6
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1 answer

What is the most generic way to provide a variable amount of outputs from a Rust function?

I am currently writing an API for machine learning algorithms in Rust and I would like for a single genetic algorithm, artificial neural network, or Bayesian network to provide multiple outputs so that for instances in which there may be redundancy,…
vadix
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6
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1 answer

Use StringLike instead of String in Scala?

Scala has the StringLike trait. Let's say I want to create a case class Name and internally it should save the name with some characters. Should I use case class Name(name: StringLike) or case class Name(name: String)? The former is obviously more…
valenterry
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5
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2 answers

Does such a design pattern exist? (Multi-Strategy/Multi-Traits)

Is there a design pattern that would allow a class from a hierarchy to 'subscribe to' concrete methods? For example, say you have an abstract base class that requires the implementation of a method. Public MustInherit Class Rule ' Common…
Igneous01
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3
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2 answers

Using PHP traits to simulate multiple inheritance

For this question I want to present my current design and my idea of using a trait. I would like to know whether my understanding of traits is correct and whether my problem can be solved with another design not involving them. My current class…
Christian Ivicevic
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3
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2 answers

How to use scala case classes when delegation is needed

Let's assume in our application we want to model cars. We also want to model a car repository where we store some registered cars. How should that be modeled in scala? Here comes my approach: First, I create a case class PlainCar. This is just a car…
valenterry
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