constructor

问题 So i know how to use it, how it works.The question what is the point in real life scenario. Imagine created class without toString() overriding. So what is the point in that class if you can't display it properly ?? And please try not to explain how constructor chaining works or something like that. I know how it works. I want to know does anyone do this in real life because without toString() overriding i don't see the point public class ConstructorChaining { String a; int b; int c; int d;

问题 I am trying to initialize all properties in class (lists) with using reflection: public class EntitiesContainer { public IEnumerable<Address> Addresses { get; set; } public IEnumerable<Person> People { get; set; } public IEnumerable<Contract> Contracts { get; set; } public EntitiesContainer() { var propertyInfo = this.GetType().GetProperties(); foreach (var property in propertyInfo) { property.SetValue(property, Activator.CreateInstance(property.GetType()), null); } } } I am getting exception

问题 Somewhere along the way, I added a constructor to my Todo class: export class Todo { id: number; title: string; complete: boolean = false; editMode: boolean = false; constructor(values: Object = {}) { Object.assign(this, values); } } I don't understand the purpose of the code in the constructor. My application seems to work both with and without it, but I am hesitant to remove the code What is the purpose of Object.assign(...) in this constructor? 回答1: This a method to easily add the values

问题 I decided to see if assigning a reference to a member would make a member a reference. I wrote the following snippet to test it. There's a simple class Wrapper with an std::string as a member variable. I take take a const string& in the constructor and assign it to the public member variable. Later in the main() method I modify the member variable but the string I passed to the constructor remains unchanged, how come? I think in Java the variable would have changed, why not in this code

问题 I have a class having Autowired Constructor. now when i am autowiring this class object in my class. how do i pass arguments for constructor?? example code: Class having Autowired Constructor: @Component public class Transformer { private String dataSource; @Autowired public Transformer(String dataSource) { this.dataSource = dataSource; } } Class using autowire for component having constructor with arguments: @Component public class TransformerUser { private String dataSource; @Autowired

问题 I want to have a derived class which has a default constructor that initializes the inheirited members. Why can I do this class base{ protected: int data; }; class derived: public base{ public: derived(){ //note data = 42; } }; int main(){ derived d(); } But not this class base{ protected: int data; }; class derived: public base{ public: derived(): //note data(42){} }; int main(){ derived d(); } error: class ‘derived’ does not have any field named ‘data’ 回答1: An object can only be initialized

问题 I mostly code in PHP and Java, but I will occasionally work on the front end of a project and use JavaScript. I usually create objects differently than below, but I came across this and it caught my interest being that the syntax is similar to what I usually program in. I was poking around, trying to figure out how to use instance variables in JavaScript classes using the syntax below. I've tried declaring the instance variables by name; , or _name; , or var name; , or all of those previous

问题 Is there a way to make groovy ignore extra attributes in a map during object instantiation? Example: class Banana{ String name } def params = [name:'someGuy', age:13] new Banana(params) In this example, groovy throws a No such property: age exception (obviously because age isn't defined in the Banana class. Without resorting to manually mapping only the desired attributes from the map to the constructor of the Banana class, is there a way to tell Banana to ignore the extra attributes? I

问题 Is there a way to make groovy ignore extra attributes in a map during object instantiation? Example: class Banana{ String name } def params = [name:'someGuy', age:13] new Banana(params) In this example, groovy throws a No such property: age exception (obviously because age isn't defined in the Banana class. Without resorting to manually mapping only the desired attributes from the map to the constructor of the Banana class, is there a way to tell Banana to ignore the extra attributes? I

问题 I'm working on developing a custom Java object persistence framework as I recently discussed in this question. One issue I am trying to solve is to force uniform annotation values in constructor parameter and method. Is it possible to know which parameter in constructor was used to set a specific field in class via reflection? For example, if constructor contains parameter String textXYZ and class contains field String textABC and in constructor I do: textABC = textXYZ (so field/parameter