interface

问题 While walking through some c++11 concepts, I came across the terms narrow contract and wide contract . But I failed to figure out a simple function example(s) which is/are written for these contracts. Can I see a simple function example that distinguishes between these two contracts? 回答1: Wide contract functions have well-defined behavior for all possible inputs, while narrow contracts mean that the functions can only be called when certain preconditions are met. Note that input might include

问题 Is there an easy way in Ruby for me to get a list of the IP addresses for all network interfaces? It needs to work in Linux/Win/OSX and I'd prefer to not have to parse ifconfig/ipconfig unless I absolutely have to. 回答1: As of Ruby 2.1, Socket#getifaddrs is available: 001:0> require 'socket' => true 002:0> Socket.getifaddrs.map { |i| i.addr.ip_address if i.addr.ipv4? }.compact => ["127.0.0.1", "192.168.1.121", "192.168.1.181"] 回答2: Check out the following post: http://coderrr.wordpress.com

问题 I have a interface like the below : public interface a { public void m1(); public void m2(); public void m3(); } public class A implements a { public void m3() { // implementation code } } I want to avoid implementation for the rest of the method. one way is to have all the methods without implementing in the class that tries to implement interface . How do I avoid this. Example code would help me understand better :) 回答1: public interface a{ public void m1(); public void m2(); public void m3

问题 I need a base class like TInterfacedObject but without reference counting (so a kind of TNonRefCountedInterfacedObject ). This actually is the nth time I need such a class and somehow I always end up writing (read: copy and pasting) my own again and again. I cannot believe that there is no "official" base class I can use. Is there a base class somewhere in the RTL implementing IInterface but without reference counting which I can derive my classes from? 回答1: In the unit Generics.Defaults

问题 I've seen a couple similar threads to this question, but none of them really answer the question I want to ask. For starters, unfortunately I'm working with existing API code so sadly, while there may be a better way to do what I'm asking about, I'm locked in to doing it similarly to the way it is because backwards compatibility is non-negotiable. I have a response class that currently contains an enum for an error code and a string description. The error codes define a fairly nice and

问题 I am playing with type assertion using the following dummy code, and I got the error: cannot type switch on non-interface value Does anyone know what does that mean? package main import "fmt" import "strconv" type Stringer interface { String() string } type Number struct { v int } func (number *Number) String() string { return strconv.Itoa(number.v) } func main() { n := &Number{1} switch v := n.(type) { case Stringer: fmt.Println("Stringer:", v) default: fmt.Println("Unknown") } } http://play

问题 I am playing with type assertion using the following dummy code, and I got the error: cannot type switch on non-interface value Does anyone know what does that mean? package main import "fmt" import "strconv" type Stringer interface { String() string } type Number struct { v int } func (number *Number) String() string { return strconv.Itoa(number.v) } func main() { n := &Number{1} switch v := n.(type) { case Stringer: fmt.Println("Stringer:", v) default: fmt.Println("Unknown") } } http://play

问题 I had an interview where interviewer asked me first what is the difference between abstract class with all the methods abstract and an interface. I replied that if it is required to inherit something in the future you will not be able to do it if you have already extended a class. Then, he stated that it was a situation where one would never have to extend any other class and you have to implement a contract. In this circumstance, which would be better, an abstract class or an interface? I

问题 I'm just about to write my first application in a duck typed language (Groovy). If I was to write the same application in a static typed language then I would need to define some interfaces. Obviously because of the duck typing in Groovy they are not actually required. At the moment I am thinking that it might make sense to define them anyway as documentation of the methods that need to be implemented in the various objects. Am I missing the point? 回答1: I've been reading on this recently here

问题 I've just started with TypeScript and I'm trying to understand why the following inline object definition isn't considered valid. I have a collection of objects - their type is irrelevant (to me), but they implement the interface so that when I iterate through them I know that the interface methods will be present in each object in the collection. I came across a "compiler" error when I tried to create an object with private information required to implement the required method: interface