constructor

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 years ago . The oops rule is "No class can exist without constructor".its ok.But in java Anonymous class can'never have its constructor.because it does not have any name. So it is contradict OOPS rule..I m really confused.Is it breaking OOPS rule?Please help 回答1: Actually, they have one implicit constructor. Suppose you

问题 I want to model the relationship between two entities, a group and an account with JPA/Hibernate. An account can have several groups, but not vice versa, so we have a OneToMany relationship between account and group. My working colleague suggested to model the entities Account and Group like public class Account { private List<Group> groups = new ArrayList<Group>(); public Account() {} public void setGroups(List<Group> usergroups) { this.groups = groups; } @OneToMany(mappedBy = "account")

问题 I want to model the relationship between two entities, a group and an account with JPA/Hibernate. An account can have several groups, but not vice versa, so we have a OneToMany relationship between account and group. My working colleague suggested to model the entities Account and Group like public class Account { private List<Group> groups = new ArrayList<Group>(); public Account() {} public void setGroups(List<Group> usergroups) { this.groups = groups; } @OneToMany(mappedBy = "account")

问题 All of the classes that I'm working on have Create()/Destroy() ( or Initialize()/Finalized() ) methods. The return value of the Create() method is bool like below. bool MyClass::Create(...); So I can check whether initialization of the instance is successful or not from the return value. Without Create()/Destroy() I can do the same job in constructor() and destructor() but I can't solve below problem. Can anyone help me? Thanks in advance. I cannot use exceptions because my company doesn't

问题 I have a following inheritance hierarchy: Class A : Form Class B : Class A Class A needs to be able to accept a parameter so that I can create the instance of Class B like this: ClassB mynewFrm = new ClassB(param); How do I define such a constructor in Class A? thanks! I am using Winforms in .net 3.5, c# EDITED: Class A and Class B are defined as forms, using partial classes. So I guess this is turning into a question about partial classes and custom (overriden) constructors. 回答1: Here is a

问题 Let's say I have multiple threads and each of them is trying to create objects of the same class. Will the simultaneous creation of objects of the same type in different threads interfere with each other? Do I need to use "lock" within the constructor? 回答1: This depends very much on the implementation of the constructor. If the constructor is only accessing members of that class, and not any external static classes or methods, then yes - it is thread safe. But if that constructor is accessing

问题 Let's say I have multiple threads and each of them is trying to create objects of the same class. Will the simultaneous creation of objects of the same type in different threads interfere with each other? Do I need to use "lock" within the constructor? 回答1: This depends very much on the implementation of the constructor. If the constructor is only accessing members of that class, and not any external static classes or methods, then yes - it is thread safe. But if that constructor is accessing

问题 An example would be: XNamespace ns = "my namespace" Why not?: XNamespace ns = new XNamespace ( "my namespace" ) What's the idea behind using implicit/explicit convertions instead of constructors? Convenience? Is there a guideline for this? 回答1: Convenience? More or less, yes. Consider the case for when you’ve got a number-like object (say, a Complex ) on which you do calculations. Clearly, writing code such as: Complex result = c1 * new Complex(2) + new Complex(32); is very annoying and hard

问题 Suppose I have the following (simplified case): class Color; class IColor { public: virtual Color getValue(const float u, const float v) const = 0; }; class Color : public IColor { public: float r,g,b; Color(float ar, float ag, float ab) : r(ar), g(ag), b(ab) {} Color getValue(const float u, const float v) const { return Color(r, g, b) } } class Material { private: IColor* _color; public: Material(); Material(const Material& m); } Now, is there any way for me to do a deep copy of the abstract

问题 class Foo { public: explicit Foo() {} explicit Foo(Foo&) {} }; Foo d = Foo(); error: no matching function for call to 'Foo::Foo(Foo)' I tried changing Foo(Foo&) to Foo(Foo) as the error suggests, which AFAIK is not a valid constructor, and sure enough I get: error: invalid constructor; you probably meant ‘Foo (const Foo&)’ What gives? How do I resolve this? (This is on GCC by the way) 回答1: There are two questionable things that you have in your copy constructor. First, you've made the copy