traits

问题 I'm trying to understand how the following class works taken from an answer from this thread: Scala Popup Menu Since the thread is pretty old I decided to just start a new question. I'm new to Scala with a Java background and I'm wondering how this class works. I read that an object with the same name as a class is like a class with a singleton object? I'm not sure how this fits in to achieving the wrapper though.. (why do we need the object?) And what exactly does the SuperMixin trait do?

问题 I'm trying to understand how the following class works taken from an answer from this thread: Scala Popup Menu Since the thread is pretty old I decided to just start a new question. I'm new to Scala with a Java background and I'm wondering how this class works. I read that an object with the same name as a class is like a class with a singleton object? I'm not sure how this fits in to achieving the wrapper though.. (why do we need the object?) And what exactly does the SuperMixin trait do?

问题 I need to update the dictionary of a mapped trait some time after initial trait creation. How do I do this? The following code: from traits.api import (HasTraits, Trait) class bar(HasTraits): zap = Trait("None", {"None": None}) def __init__(self): # In reality, determined programmatically at runtime. add_dict_entries = {"One": 1} new_dict = {"None": None} new_dict.update(add_dict_entries) self.zap = Trait("None", new_dict) theBar = bar() yields: Traceback (most recent call last): File "tst

问题 I recently came across Traits in PHP and I'm trying to understand them. During my research I stumbled upon this Stack Overflow question: Traits vs. Interfaces. The accepted answer mentions the following: An interface defines a set of methods that the implementing class must implement. When a trait is use'd the implementations of the methods come along too--which doesn't happen in an Interface. So far so good but this sounds exactly like the difference between an interface and an abstract

问题 Apart from the inheritance aspect, is there a difference between the following class templates: 1| trait TraitA extends TraitB 2| trait TraitA { self: TraitB => } I would like to split responsibilities between TraitA and TraitB but the former cannot function without the latter. How would you express this intent? To me solution [2] would be the more natural approach. However I do not want to put the burden on implementers mixing in what needs to be mixed in anyway. 回答1: My preference is

问题 I'm currently working on a huge javascript project which has a huge class hierarchy and heavily uses mixins to extend functionality of base classes. Here is an example of how mixin looks like, we're using compose library to create class-like objects: // Base.js var Base = compose({ setX: function (x) { this.x = x; }, setY: function (y) { this.y = y; }, setPosition: function (x, y) { this.setX(x); this.setY(y); } }) // SameXAndY.js - mixin var SameXAndY = compose({ // Executes after setX in

问题 Is there a way to specify that a trait has to provide a concrete implementation of a method? Given some mixin class A extends B with C { foo() } The program will compile if either of A , B , or C implements foo() . But how can we force, for example, B to contain foo 's implementation? 回答1: You can do the following: class A extends B with C { super[B].foo() } This will only compile if B implements foo . Use with caution though as it (potentially) introduces some unintuitive coupling. Further,

问题 I would like to wrap a non-Traits model class for use with Python Traits. My goal is to write a Traits-based UI to manipulate an "external" model class. The external model class has been generated by SWIG and so I cannot add enthought.traits.api.HasTraits as an ancestor (I think, though I may be wrong). My current best attempt is from enthought.traits.api import HasStrictTraits, Property, Instance class ExternalModel(): foo = 'foo' class TraitsModel(HasStrictTraits): _e = Instance

问题 So, I was trying to make a finagle server, talk to sentry (not important), and stumbled upon a case, where I needed to inherit from two classes (not traits) at the same time, let's call them class SentryHandler extends Handler and class TwitterHandler extends Handler , and assume, that I need to create MyHandler , that inherits from both of them. After a moment of stupidity, when I thought it was impossible without using a dreaded "delegation pattern", I found a solution: trait SentryTrait

问题 I have a trait trait B { type Index: Sized + Copy; fn bounds(&self) -> (Self::Index, Self::Index); } I want to get all the Index es within bounds : fn iterate<T: B>(it: &T) { let (low, high) = it.bounds(); for i in low..high {} } This won't work since there's no constraint that the type T can be "ranged" over, and the compiler says as much: error[E0277]: the trait bound `<T as B>::Index: std::iter::Step` is not satisfied --> src/main.rs:8:5 | 8 | for i in low..high {} | ^^^^^^^^^^^^^^^^^^^^^