composition

问题 Is it possible to compose for example: (defn- multiple-of-three? [n] (zero? (mod n 3)) (defn- multiple-of-five? [n] (zero? (mod n 5)) into: multiple-of-three-or-five? so I can use it for filtering: (defn sum-of-multiples [n] (->> (range 1 n) (filter multiple-of-three-or-five?) (reduce +))) Also I don't want to define it like this: (defn- multiple-of-three-or-five? [n] (or (multiple-of-three? n) (multiple-of-five? n))) For example with Javascript module Ramda it would be achieved as: http:/

问题 I'm still learning Golang and I want to ask something. Is it possible to do something like this and passing any other child to PMethod that extending Parent struct? type Parent struct{ PAttribute string } func (p *Parent) PMethod(c *Child){ fmt.Println("this is parent Attribute : " + p.PAttribute) fmt.Println("this is child Attribute : " + c.CAttribute) } type Child struct{ Parent CAttribute string } type Child2 struct{ Parent CAttribute string } func main(){ c := Child{ Parent{ "parent" },

问题 In my concrete class I need to implement (set public) only certain methods of an abstract class. So I cannot extend it beacause all the abstract methods are public. I could use composition, and forward just methods I need, but I obviously need to implement the abstract class. So, I'm wondering, is it a good approach to implement an abstract class in a private class and then forward in the parent class only the needed methods of the inner class? For example: public class ConcreteClass{ private

问题 I have this domain model: class Person < ActiveRecord::Base composed_of :address, mapping: [%w(address_street street), %w(address_city city), %w(address_zip_code zip_code), %w(address_country country)] validates :name, presence: true, length: { maximum: 50 } validates :surname, presence: true, length: { maximum: 50 } validates_associated :address end class Address include ActiveModel::Validations include ActiveModel::Conversion extend ActiveModel::Naming attr_reader :street, :city, :zip_code,

问题 I'm practicing java by building a simple directory. I have 4 Classes. These are: Person Address Contact testClass I have already finished creating this system and it works the way I want it. I did this by making 3 different arrays for the Person, Address and Contact. To link the Person, Address and Contact together I place them on there respective array with the same index number. (Not literally linking them together, just a way to know which address or contact to access when editing a person

问题 I think I understand the difference between interface and abstract. Abstract sets default behavior and in cases of pure abstract, behavior needs to be set by derived class. Interface is a take what you need without the overhead from a base class. So what is the advantage of interface over composition? The only advantage I can think is use of protected fields in the base class. What am I missing? 回答1: An interface defines how you will be used. You inherit in order to be reused. This means you

问题 I am currently planning the design for a new system I will need to code that interacts with a back-end API. I was contemplating object composition and inheritance and decided that the most correct procedure in my situation would be to go with composition over inheritance as my objects have a "has a" relationship to one another and not an "is a". I find now though that because some objects are reliant on other, there may be cases were "object A" has an attribute which is "object B" and an

问题 Say I have a mean function defined like so: mean xs = sum xs / (fromIntegral $ length xs) but I want it in some tacit form, like this: mean = sum / (fromIntegral . length) Is there a built-in Haskell way to do something along these lines without having to build up my own tacit function (something like this): tacit :: (a -> b -> c) -> (d -> a) -> (d -> b) -> d -> c tacit a b c i = a (b i) (c i) In this form, the function looks like this: mean = tacit (/) sum (fromIntegral . length) but it

问题 I understand the basics of function composition in F#, as, for example, described here. Maybe I am missing something, though. The >> and << operators seem to have been defined with the assumption that each function only takes one argument: > (>>);; val it : (('a -> 'b) -> ('b -> 'c) -> 'a -> 'c) = <fun:it@214-13> > (<<);; val it : (('a -> 'b) -> ('c -> 'a) -> 'c -> 'b) = <fun:it@215-14> What I'd like to do, however, is something like the following: let add a b = a + b let double c = 2*c let

问题 Scala functions has following methods for chaining: fn1.andThen(fn2) fn1.compose(fn2) But how can be written this case: I have function cleanUp() which has to be called always as last step. And I have a bunch of other functions, like that: class Helper { private[this] val umsHelper = new UmsHelper() private[this] val user = umsHelper.createUser() def cleanUp = ... // delete user/ and other entities def prepareModel(model: TestModel) = { // create model on behalf of the user } def commitModel(