mixins | 易学教程

Python Mixin - Unresolved Attribute Reference [PyCharm]

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问题 I am using a mixin to separate a range of functionality to a different class. This Mixin is only supposed to be mixable with the only child class: class Mixin: def complex_operation(self): return self.foo.capitalize() class A(Mixin): def __init__(self): self.foo = 'foo' in my method Mixin.complex_operation PyCharm gives warning 'Unresolved Attribute Reference foo'. Am I using the mixin pattern correctly? Is there a better way? (I would like to have type hints and autocompletion in my mixins,

understanding comparable mixin and enumerable mixin

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问题 I am a newbie and learning ruby. Would like to have a better understanding of the question asked. I don't understand the use of comparable mixin and enumerable mixin. I mean we don't include these in our class when we need to use them, right? if we want to compare two objects we simply write x > y. Then what is the use of explicitly using them? 回答1: Great Question Akash! Sometimes it's not "simple" how two objects can be compared! What if you have a Dog class? How do you compare two Dog

How to solve “Implementation restriction: trait … accesses protected method … inside a concrete trait method.”

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问题 A Java library class I'm using declares protected getPage(): Page { ... } Now I want to make a helper Scala mixin to add features that I often use. I don't want to extend the class, because the Java class has different subclasses I want to extend at different places. The problem is that if I use getPage() in my mixin trait , I get this error: Implementation restriction: trait MyMixin accesses protected method getPage inside a concrete trait method. Is there a solution how to make it work,

Single Responsibility and Mixins

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问题 Given that Mixins generally introduce new behaviour into a class, this generally implies that a class would have more than one behaviour. If a class has a single responsibility this is defined as the class having only one reason for change. So, I can see this from two different perspectives The class only has one reason for change. The module mixed in also has only one reason for change. If the class is changed only the class will need retesting. If the module is changed only the module needs

Scala compiler cannot infer mix-in type for pattern matching

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问题 I have a use case for algebraic groups over finite permutation sets. Because I would like to use the group for various permutation classes which are otherwise unrelated, I would like to do this as a mix-in trait. Here's an excerpt of my attempt trait Permutation[P <: Permutation[P]] { this: P => def +(that: P): P //final override def equals(that: Any) = ... //final override lazy val hashCode = ... // Lots of other stuff } object Permutation { trait Sum[P <: Permutation[P]] extends Permutation

Alternatives to abstract classes in Ruby?

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问题 I am new to Ruby. A simple example, what I need: class Animal abstract eat() class Cat < Animal eat(): implementation class Dog < Animal eat(): implementation In other words, the eat() method should be required for all the classes which extend Animal. In JAVA I would just use an abstract class, but after doing some research I found that many people don't use it in Ruby and mixin / modules are recommended instead. However, I don't understand, if modules can do more than just include an

Is mixin considered a design pattern?

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问题 Are mixins considered a design pattern? Structural? 回答1: They're a language feature. A "pattern" is different from a feature, in that it resolves a set of forces that may influence a situation in contradictory ways. Features, by their presence or absence, tend to create the forces that patterns resolve. Many design patterns (Double Dispatch is a good example) came about to work around language limitations (in this case method dispatching on a single argument). 回答2: Yes, it is in Ruby. Design

Can you test if a mixin exists?

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问题 Sass quick question (hopefully) here. Can you test for the existence of a mixin? e.g. @if thumbnail-mixin {} @else { //define mixin }. Ideally I'd use @unless , but that only exists on a fork. I'm aware you can overwrite a mixin but I'm thinking more if you can have a default mixin, rather than having to specify N variables in every case. 回答1: Sass does not currently have native functionality to determine if a mixin exists or not. https://github.com/nex3/sass/issues/561#issuecomment-14430978

Mixins in Tapestry5

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问题 I'm new to Tapestry5, but because of an internship I need to work with it. Currently I am trying to build a mixin to integrate a CSRF token (explanation here) to any form. Is it even possible to achieve this in a mixin? If yes, could I access functions that the mixin offers from the page? I am really not sure about how mixins really work and I'm having big difficulties on finding information about how to create one. Can somebody explain how to create a mixin and if what I'm trying to do is

LESS: concatenate multiple background rules

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I have a mixin that creates a gradient with vendors' prefixes, and I would like to add this background to a DIV in addition to another background-image . .horizontal(@start-color: #555; @end-color: #333; @start-percent: 0%; @end-percent: 100%) { background:@start-color; background-image: -webkit-linear-gradient(left, @start-color @start-percent, @end-color @end-percent); background-image: -o-linear-gradient(left, @start-color @start-percent, @end-color @end-percent); background-image+: linear-gradient(to right, @start-color @start-percent, @end-color @end-percent); background-repeat: repeat-x;