constructor

问题 I have a class of form something like this: class A{ public function __constructor(classB b , classC c){ // } public function getSum(var1, var2){ return var1+var2; } } My test case class is something like this: use A; class ATest extends PHPUnit_Framework_TestCase{ public function testGetSum{ $a = new A(); $this->assertEquals(3, $a->getSum(1,2)); } } However when I run the phpunit, it throws some error like: Missing argument 1 for \..\::__construct(), called in /../A.php on line 5 Even if I

问题 Is it wrong to have a lot of parameters inside a constructor? Like 10 to 15 parameters? Because I was designing a class where a constructor will have lots of parameters, for example, a Person class. My example person class has 6 parameters in its constructor: public class Person { private String fName; private String lName; private String mInitial; private int age; private String contactNumber; private String emailAddress; public Person(String fName, String lName, String mInitial, int age,

问题 I am trying to integrate pubnub-react in react native. Here's my code: import React, { Component } from 'react'; import PubNubReact from 'pubnub-react'; import {key1,key2} from '../config.js export default class extends Component { constructor(props) { super(props); this.pubnub = new PubNubReact({ publishKey: key1, subscribeKey: key2 }); this.pubnub.init(this) } render() { return null } } This is throwing this error: [[TypeError: Object is not a constructor (evaluating 'new _pubnubReact

问题 I am trying to integrate pubnub-react in react native. Here's my code: import React, { Component } from 'react'; import PubNubReact from 'pubnub-react'; import {key1,key2} from '../config.js export default class extends Component { constructor(props) { super(props); this.pubnub = new PubNubReact({ publishKey: key1, subscribeKey: key2 }); this.pubnub.init(this) } render() { return null } } This is throwing this error: [[TypeError: Object is not a constructor (evaluating 'new _pubnubReact

问题 I'm writing a custom API using Reflection to save Objects to file. I have the following class structure: @Constructor public XYZPOJO(@Key(key = "word") String word, @Key(key = "variations") ArrayList<String> varList) { this.word = word; this.varList = varList; } String word; ArrayList<String> varList = new ArrayList<String>(); @Key(key = "word") public String getWord() { return word; } @Key(key = "variations") public ArrayList<String> getVarList() { return varList; } When saving Object to

问题 I'm pretty new to OOP and I need some help understanding the need for a constructor in a python class. I understand init is used to initialize class variables like below: class myClass(): def __init__ (self): self.x = 3 print("object created") A = myClass() print(A.x) A.x = 6 print(A.x) Output: object created 3 6 but, I could also just do, class myClass(): x = 3 print("object created") A = myClass() print(A.x) A.x = 6 print(A.x) which prints out the same result. Could you please explain why

问题 I'm pretty new to OOP and I need some help understanding the need for a constructor in a python class. I understand init is used to initialize class variables like below: class myClass(): def __init__ (self): self.x = 3 print("object created") A = myClass() print(A.x) A.x = 6 print(A.x) Output: object created 3 6 but, I could also just do, class myClass(): x = 3 print("object created") A = myClass() print(A.x) A.x = 6 print(A.x) which prints out the same result. Could you please explain why

问题 First attempt and everything works fine: class Base { public: Base() {std::cout << "default ctor!\n"; } }; ... Base b{}; Base b_one = {}; Another way of implementation(add explicit ): class Base { public: explicit Base() {std::cout << "default ctor!\n"; } }; ... Base b{}; Base b_one = {}; // error! Why? I have read on cppreference that in both cases default initialization would be used and no diffences. From list initialization: Otherwise, If the braced-init-list is empty and T is a class

问题 My debugging work in IE ended today by finding that constructor.name is undefined . I created the following simple code that reproduces the issue: ({}).constructor.name === undefined // => true Is there any workaround to make this work? Maybe overriding somehow the prototype? If possible, I don't want to change the syntax, because the change would be major. JSFIDDLE 回答1: The problem is simply that the name property of function objects is not supported in Internet Explorer. The property is non

问题 In the following example, why is myList null when no parameter is passed to the constructor? I declare it as an empty ( growable ) list in the class. class MyListClass { List myList = []; MyListClass({this.myList}); } void main() { final obj = MyListClass(); assert(obj.myList != null); } What is the best way to pass an optional list, but default to an empty list? I know you can do the following, but maybe there is a better way? MyListClass({this.myList}) { this.myList ??= []; } UDATE: This is