Thread: Please check my C++

OK, three things:
_date should probably be date_ instead. Underscore identifiers are typically reserved for implementation.
2) I forgot: you don't need the "struct" keyword here in C++ - all you need is "tm* timeinfo" - no more!
3) What are you trying to do?

Then call setDate inside the Date constructor, but what's this about?

Code:

Class A
{
private:
     Date currentDate(Date::getCurrentTime());   // Is this correct?
};

And you want to do...

Code:

Date::Date()
{
SetDate( getCurrentTime() );
}

?

I think I get what you are trying to do. You are trying to initialize the members of class A, yes?
In that case, you initialize them via the constructor:

Code:

A::A(): /* Initializer list */ startDate(startDate.getCurrentTime()), endDate(something)
{
}

Although, better might be to make the default date constructor store the current time in itself, so the constructor for A would then be:

Code:

A::A(): /* Initializer list */ startDate(), endDate(something)
{
}

No, you probably want to make "currentTime" a static function, so that you can call it without having a valid Date object.

Then you could do:

Code:

Contract::Contract(): issued( Date::getCurrentTime() )

--
Mats

1) The ":" symbolizes the beginning of the initializer list. Everything in the initializer list calls the constructor of what you put there. There it is mandatory, for example, if you have a base class with a constructor that takes one argument. You'll have to use the initializer list to call the correct constructor with the correct argument.

2) That's why I said probably make the constructor get the default time.

3) There are two issues:
3a) It's invalid syntax - you can't call a constructor after the object is constructed. You can only assign. Again, this leads to unnecessary waste of resources.
3b) It's typically undefined behavior to call a member function of a class before it's constructed, so it's very bad.

4) Since getCurrentTime does not rely on the object it's a member of (it only gets the current system time and not the current time embedded in the object), it's better to make it static as mats suggests. That way you can call it without having to worry about constructing the object first.

Originally Posted by Elysia

2) That's why I said probably make the constructor get the default time.

Elysia, i would also like to initialize a time object with zeros, not current time...

4) Since getCurrentTime does not rely on the object it's a member of (it only gets the current system time and not the current time embedded in the object), it's better to make it static as mats suggests. That way you can call it without having to worry about constructing the object first.

I don't know if i understand you, where did mats say this [EDIT: Sorry i missed his post]? anyway, here's my date class with now 'static' keyword...

Code:

class Date						
{
public:
	Date();
	Date(tm dt);
	void SetDate(tm dt);
	static tm getCurrentTime();
	int getDay();
	int getMonth();
	int getYear();
	int getHour();
	int getMinute();
	tm getLocalDT();
private:
	int day;
	int month;
	int year;
	int hour;
	int minute;
	tm local_dt;
};

// Get the local date and time of system
static tm Date::getCurrentTime()
{
	time_t rawtime;
	tm* timeinfo;

	time( &rawtime );
	timeinfo = localtime ( &rawtime );

	return *timeinfo;
}

What difference that this 'static' function make?

Originally Posted by csonx_p

Elysia, i would also like to initialize a time object with zeros, not current time...

But initializing them with 0s doesn't make much sense, does it? It's an invalid date.

I don't know if i understand you, where did mats say this?

Just above my previous reply.

anyway, here's my date class with now 'static' keyword...

You should put static only in front on the definition, not the implementation and it would be correct.

What difference that this 'static' function make?

Basically, it does so that all of the classes share only one instance of the function. The reason is that getCurrentTime is not bound to the object - your class. It does nothing of the sort - it doesn't return the time of the object, it doesn't set the time in the object.
There it should better be static or you can make it a free function.

A static function is not passed a "this" pointer of the current class object - which means that it's basically a free function, but it's described within a class. This means that you can call it without having an existing object.

You can't call a constructor with the object that it is constructing. That's like using the car you are building to transport the bits you need to build the car - doesn't work, right? [yes, you could have a "half-finished car" - but computers don't work well with "half-done" things].

You also can't call one constructor from another constructor, e.g.

Code:

class X
{
   X() {
     X(0);   // calling X(int x) with zero - not valid. 
   };
   X(int x)
   {
     ... 
   };
}

--
Mats