class

问题 I am trying to lazy-load data from the server into a Map. For that reason I would like to add functionality to Map, so that when a key doesn't exist, a call is done to get the value . What I tried is this: class LazyMap extends Map { // use .length for now. When this works, go use xhr operator [](key) => LazyMap.putIfAbsent(key, () => key.length); } LazyMap test = new LazyMap(); main() { print(test.containsKey('hallo')); // false // I prefer to use this terse syntax and not have to use

问题 Can anyone helps me understand why this is this giving me an error? The error being "NameError: name 'self' is not defined". I have a similar class higher up in my code and that works fine? I'm using 'xlrd' and team is a reference to a workbook.sheet_by_name. class Rollout: def __init__(self, team, name): self.team = team self.name = name self.jobs = {} self.start_row = 1 self.last_row = self.team.nrows for i in range(self.start_row,self.last_row): try: self.jobs[i-1] = [str(self.team.cell

问题 This question already has answers here : Calling class staticmethod within the class body? (5 answers) Closed 2 years ago . Let's assume I have a class, with a static method, and I want a class property to be set to the value that this method returns: class A: @staticmethod def foo(): return 12 baz = foo() But doing this I get an error: Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 5, in A TypeError: 'staticmethod' object is not callable I found a

问题 I have a situation that looks like the following code: #include <iostream> class A { public: A() { std::cout << "A created!" << std::endl; } ~A() { std::cout << "A destroyed!" << std::endl; } virtual const char* Name() { return "A"; } }; class B : public A { public: B() { std::cout << "B created!" << std::endl; } ~B() { std::cout << "B destroyed!" << std::endl; } const char* Name() { return "B"; } }; int main() { A* a = new B(); std::cout << a->Name() << "\n"; delete a; return 0; } I want B

问题 Why the following code doesn't compile? namespace mtm { template<class T> class Matrix { private: public: class AccessIllegalElement; }; Matrix::AccessIllegalElement{}; } I'm trying to implement the inner class for handling errors Error I get: 'Matrix' is not a class, namespace, or enumeration Plus, if inside AccessIllegalElement I want to write a function that prints the illegal index what is preferable? 1) to define a function that takes one parameter 2) to give every class object a member

问题 Full Code at https://codepen.io/CodeLegend27/pen/ExPZRxa did read similary articles but didnt managed to solve it so my array looks like this: I have this loop for (let i = 0; i < ultraarr.length; i++) { ultraarr.sort(); $(".row").append(ultraarr[i].display()) } this calls the function display which is a class function and it basically inserts the data into html. What i want it to DO: i want it ordered according to the dates ascending. did research the a-b stuff but cant see the solution for

问题 I wrote the following code using C++11 standard: .h file: #include "Auxiliaries.h" class IntMatrix { private: Dimensions dimensions; int *data; public: int size() const; IntMatrix& operator+=(int num); }; Bit I am getting and error saying that: error: use of overloaded operator '+' is ambiguous (with operand types 'const mtm::IntMatrix' and 'int') return matrix+scalar; Any idea of what causes this behaviour and how may I fix it? 回答1: You declared the operators in the mtm namespace so the

问题 new to Dart here, sorry in advance if this is a redundant question; I couldn't find the answer. I created a function simulateRequest and then passed it to its own class SimReq and saved it in a file on its own. I imported the class in the main file, but when I try to execute it, I get an error, here is the class code: class SimReq { void simulateRequest() async { // first future holds family name String famNameFunc = await Future.delayed(Duration(seconds: 2), (){ String famName = 'Shanshi';

问题 Good afternoon. I started discussing this issue here, but I thought that the topic is worthy of a separate question, since I could not find the answer “from the swipe”. Panee was discussed at StaskOverflov Thanks to this decision, changes were made to the class (new full code). Now the changed type of the class is as follows: class Seasonality_ProgressBar : Control #region --События-- public delegate void OnValueChangedEvent(int value); public event OnValueChangedEvent OnValueChanged;

问题 E.g., I have an empty function to clear a linked list: void empty(Node* head) { if (head->next) { empty(head->next); } delete head; head = nullptr; } But then I created a class for the linked list, so now I don't need to pass the head argument: void empty() { if (head->next) { empty(head->next); } delete head; head = nullptr; } But empty(head->next) line is obviously wrong as empty doesn't take any arguments. The idea comes to my mind to create a function inside a function (with lambda),