constructor

问题 Are there any details on whether or not an object is cleaned up using finalize() if that object's constructor thew an exception. When this method is called is notoriously ill defined. According to the manual: The Java programming language does not guarantee which thread will invoke the finalize method for any given object. It is guaranteed, however, that the thread that invokes finalize will not be holding any user-visible synchronization locks when finalize is invoked. If an uncaught

问题 I'm trying to use Kotlin in my Android project. I need to create custom view class. Each custom view has two important constructors: public class MyView extends View { public MyView(Context context) { super(context); } public MyView(Context context, AttributeSet attrs) { super(context, attrs); } } MyView(Context) is used to instantiate view in code, and MyView(Context, AttributeSet) is called by layout inflater when inflating layout from XML. Answer to this question suggests that I use

问题 Recently read in a article on dotnetpearls.com here saying that static ctors take a substantial amount of perfomance hit. Could not fathom why? 回答1: I think "substantial" is an overstatement in most use cases. Having a static constructor (even if it does nothing) affects type initialization time due to the presence/absence of the beforefieldinit flag. There are stricter guarantees about timing when you have a static constructor. For most code, I'd suggest this doesn't make much difference -

问题 Please help me with this. I was trying to fix this for two hours. This is my code. class deviceC { private: deviceA devA; deviceB devB; wayPoint destination,current; public: deviceC(wayPoint destination1){ destination=destination1; devA=deviceA(); devB=deviceB(); } }; This is the error: cannot find default constructor to initialize member 'deviceC::destination' in function deviseC::destination(wayPoint) 回答1: You need an initializer list in your constructor, because member destination and

问题 Please help me with this. I was trying to fix this for two hours. This is my code. class deviceC { private: deviceA devA; deviceB devB; wayPoint destination,current; public: deviceC(wayPoint destination1){ destination=destination1; devA=deviceA(); devB=deviceB(); } }; This is the error: cannot find default constructor to initialize member 'deviceC::destination' in function deviseC::destination(wayPoint) 回答1: You need an initializer list in your constructor, because member destination and

问题 I'm writing a C++ application in which I have a Controller class with two nested structs, defined in my header file as follows: class Controller { struct help_message { // controller.hpp, line 19 std::string summary; std::string details; help_message(const std::string&, const std::string&); }; struct player_command { cmd_t cmd; help_message help; // cmd_t is my own typedef, irrelevant for this question player_command(const cmd_t&, const help_message&); }; // more members... }; In my source

问题 I'm trying to persist Maps of properties as single JSON-encoded columns, as shown in this question. The problem I'm having is that apparently transient properties cannot be set in the default map constructor . Given any transient field: class Test { //... String foo static transients = ['foo'] } It seems that the map constructor (which Grails overrides in various ways) simply discards transient fields: groovy:000> t = new Test(foo:'bar') ===> Test : (unsaved) groovy:000> t.foo ===> null While

问题 The MFC's root object CObject's copy constructor and assignment are disabled by default. In MSDN, there is a description The standard C++ default class copy constructor does a member-by-member copy. The presence of the private CObject copy constructor guarantees a compiler error message if the copy constructor of your class is needed but not available. You must therefore provide a copy constructor if your class requires this capability. In CObject's source code, there is a comment: Disable

问题 I am trying to create a shared library in Linux. How can I pass an argument to function my_load() when library is loaded? In my C application, I make a call to test_func() then it automatically executes my_load() first before the called function then lastly it executes my_unload() #include <stdio.h> void __attribute__ ((constructor)) my_load(int argc, char *argv[]); void __attribute__ ((destructor)) my_unload(void); void test_func(void); void my_load(int argc, char *argv[]) { printf("my_load:

问题 I am trying to create a shared library in Linux. How can I pass an argument to function my_load() when library is loaded? In my C application, I make a call to test_func() then it automatically executes my_load() first before the called function then lastly it executes my_unload() #include <stdio.h> void __attribute__ ((constructor)) my_load(int argc, char *argv[]); void __attribute__ ((destructor)) my_unload(void); void test_func(void); void my_load(int argc, char *argv[]) { printf("my_load: