I know that namespace are preferred in C++ if you want to define static functions, but what to do when you have functions which access other functions but the other functions should be private and not be accessible by others. How to declare/define it ? Wouldn't it be much simple to use classes ? Or do I have to still use namespaces ?
Like this:
class Test1
{
public:
static void Start()
{
if(1) // Some checks...
{
ProcessStart();
}
}
private:
static void ProcessStart()
{
if(!Initialized)
{
//Initialize
}
// Do other stuff
}
static bool Initialized;
};
bool Test1::Initialized = false;
You don't need to expose private details in the public API:
foo.hpp:
#ifndef H_FOO
#define H_FOO
namespace Foo
{
void Start();
}
#endif
foo.cpp:
#include "foo.hpp"
namespace Foo
{
namespace
{
void ProcessStart()
{
// ...
}
}
void Start()
{
ProcessStart();
}
}
Only the header file ends up in your public /include directory, so nobody will ever know that there are private implementation functions (except perhaps your debugger).
Related
I am trying to use QTConcurrent class to launch some tasks asynchronously but I am getting some errors:
This is my code:
class A {
public:
void method1();
};
class B {
std::unique_ptr<A> ptr;
public:
void method2() {
QtConcurrent::run(&this->ptr, &A::method1);
}
}
I get compilation error.
Could someone tell me what the correct syntax is?
Thanks in advance and regards
I finally was able to find working version:
class A {
public:
void method1();
};
class B {
std::unique_ptr<A> ptr;
public:
void method2() {
QtConcurrent::run(this->ptr.get(), &A::method1);
}
}
I have written a custom OnMethodBoundaryAspect called TraceAspect. This aspect checks within the OnEntry, OnExit, and OnException methods whether tracing is enabled or not. I have a central class for reading and writing settings. Both of the two methods Settings.GetLoggingEnabled() and Settings.GetLogLevel() are called from the TraceAspect. They are there, so I reuse them which results in a StackOverflowException.
[assembly: MyCompany.MyProduct.TraceAspect]
[Serializable]
public class TraceAspect : OnMethodBoundaryAspect
{
public override void OnEntry(MethodExecutionArgs args)
{
if (Settings.GetLogginEnabled() && Settings.GetLogLevel() == LogLevel.Trace)
{
// Log the message
}
}
}
Applying the [TraceAspect(AttributeExclude = true)] attribute to the TraceAspect class leads to the same behaviour.
I could write something like this. But this is code duplication.
[assembly: MyCompany.MyProduct.TraceAspect]
[Serializable]
public class TraceAspect : OnMethodBoundaryAspect
{
public override void OnEntry(MethodExecutionArgs args)
{
if (this.GetLogginEnabled() && this.GetLogLevel() == LogLevel.Trace)
{
// Log the message
}
}
private bool GetLoggingEnabled()
{
// copy code from Settings.GetLogginEnabled()
}
private bool GetLogLevel()
{
// copy code from Settings.GetLogLevel()
}
}
How can I tell that the Settings.GetLoggingEnabled() and Settings.GetLogTrace() methods should not be traced, when they are called by the aspect?
You can break the recursion during logging by introducing a thread static flag to indicate that you're currently inside the logging call.
[Serializable]
public class TraceAspect : OnMethodBoundaryAspect
{
[ThreadStatic]
private static bool isLogging;
public override void OnEntry(MethodExecutionArgs args)
{
if (isLogging) return;
isLogging = true;
try
{
if (Settings.GetLogginEnabled() && Settings.GetLogLevel() == LogLevel.Trace)
{
// Log the message
}
}
finally
{
isLogging = false;
}
}
}
I'm writing C++ code that calls C# code. The C# may need to invoke methods back in the C++ code. If both parts were C# I think I would use following mechanism. Please note I pass EventHandler from ShouldBCpp to Csharp instead of registering in ShouldBCpp since ShouldBCpp does not know what csharp points to (& can't change CsharpBase).
public abstract class CsharpBase
{
public abstract void SomeMethodDoingActionInB();
}
public class Csharp : CsharpBase
{
public Csharp(EventHandler f)
{
MySpecialHook += f;
}
public event EventHandler MySpecialHook;
public override void SomeMethodDoingActionInB()
{
if (MySpecialHook != null)
MySpecialHook(this, null);
}
}
public class ShouldBCpp
{
public CsharpBase csharp;
public ShouldBCpp()
{
csharp = new Csharp(NotificationFromClassB); // actually using Activator::CreateInstance
}
public void NotificationFromClassB(object sender, EventArgs e)
{
}
public void Go()
{
csharp.SomeMethodDoingActionInB();
}
}
class Program
{
static void Main(string[] args)
{
ShouldBCpp shouldBCpp = new ShouldBCpp();
shouldBCpp.Go();
}
}
Question is how to write ShouldBCpp in C++/CLI. Bonus points for using delegate :)
Thank you
A simple translation to C++/CLI would look like this:
public ref class IsCppCLI
{
public:
CsharpBase^ csharp;
IsCppCLI()
{
csharp = gcnew Csharp(gcnew EventHandler(this, &IsCppCLI::NotificationFromClassB));
// You didn't show your Activator code,
// but I believe it would translate to C++/CLI as this:
csharp = dynamic_cast<CsharpBase^>(
Activator::CreateInstance(
Csharp::typeid,
gcnew array<Object^> {
gcnew EventHandler(this, &IsCppCLI::NotificationFromClassB)}));
}
void NotificationFromClassB(Object^ sender, EventArgs^ e)
{
}
void Go()
{
csharp->SomeMethodDoingActionInB();
}
}
This is a class library clr/c++ project.
Class A is unmanaged c++, class B managed c++.
I would like to create an object of B from a C# application and call the "void Sign" with that object and catch the StatusEvent in C#.
How to call B::Showsts from A::call_A in order to achieve this? Please keep in mind that call_A is called from a delegate of the B class object.
Thank you in advance!
public class A{
public:
int call_A();
};
public ref class B{
private:
A* a1;
public:
void Sign(String^ ufile);
void Showsts(string sts);
delegate void GetResult(String^);
event GetResult^ StatusEvent;
SpyrusLib(void){
a1=new A();
}
protected: ~SpyrusLib(){
delete a1;
}
private:
String^ str;
delegate int MySignDelegate(String^);
int MySign(String^ file);
void Callbacksign(IAsyncResult ^ar);
};
void B::Sign(String^ ufile){
MySignDelegate^ signDel = gcnew MySignDelegate( this, &B::MySign );
AsyncCallback^ cb = gcnew AsyncCallback( this, &B::Callbacksign);
signDel->BeginInvoke( ufile , cb, signDel );
}
int B::MySign(String^ file){
stdstr=msclr::interop::marshal_as<std::string>(file);
a1->call_A(stdstr);
}
void B::Showsts(string sts){
str = gcnew String(sts.c_str());
StatusEvent(str);
}
int A::call_A(string stat){
?-Showsts(stat);
}
I'm not sure it's the best solution but I solved it adding the following things to the classes:
typedef void (__stdcall * Unmanagedstatus)(string sts);
using namespace std;
public class A{
private:
Unmanagedstatus sendmsg;
public:
int call_A();
spyrus(Unmanagedstatus unm)
{
sendmsg=unm;
}
};
public ref class B
{
private:
delegate void Managedstatus(string);
Managedstatus^ managed;
IntPtr unmanaged;
A* a1;
public:
SpyrusLib(void)
{
managed = gcnew Managedstatus(this, &B::Showsts);
unmanaged = Marshal::GetFunctionPointerForDelegate(managed);
a1=new A((Unmanagedstatus)(void*)unmanaged);
}
}
int A::call_A(string stat){
sendmsg(stat); // this will call B::Showsts and the events raised
//from Showsts are also working in the C# app
}
I have an interface, and I was trying an example on dynamic polymorphism as follows:
#include <iostream>
using namespace std;
class foo{
public:
virtual void set();
virtual void printValue();
};
class fooInt : public foo{
private:
int i;
public:
int get(){
return i;
}
void set(int val){ //override the set
i = val;
}
void printValue(){
cout << i << endl;
}
};
int main(){
foo *dt; //Create a base class pointer
dt = new fooInt; //Assign a sub class reference
dt->set(9);
}
However when I compile this, I get no matching function for call to ‘foo::set(int)’. Where am I going wrong? I tried to read this article, and I still couldn't figure out the mistake.
class foo has no method set(int). It has a method set(), but no method set(int).
If you intend to override an inherited method, the superclass method and your method must have the same signature:
class foo {
...
// If you really want an abstract class, the `= 0`
// ensures no instances can be created (makes it "pure virtual")
virtual void set(int) = 0;
...
}
This is because your definition of
virtual void set();
Should be
virtual void set(int val);
The corrected program is given here
#include <iostream>
using namespace std;
class foo {
public:
virtual void set(int val)=0;////////here you have void set() function with no argument but you tried to override void set(int val) which take one argument.
virtual void printValue()=0;
};
class fooInt : public foo{
private:
int i;
public:
fooInt()
{
cout<<"constructor called\n";
}
int get(){
return i;
}
void set(int val){ //override the set
i = val;
}
void printValue(){
cout << i << endl;
}
};
int main(){
foo *dt; //Create a base class pointer
dt=new fooInt;
dt->set(9);
dt->printValue();
}
Fault of the previous program were
1.You tried to override set() {no argument} with set(int val){one argument}.
2.When a class contain a pure virtual function,it must be implemented by its derived classes.
3. No object can be created of a class which contain a pure virtual function.But ref can be created.
Thanks