I have a struct as follows:
struct temp
{
char* person;
char* address;
int id;
int phone;
}
And I have a struct variable as
temp var;
I wish to initialize the member of the structs in a constructor like:
Data ( )
{
var -> person = {};
var -> address = {};
var.id = 0;
var.phone = 0;
..............
}
person and address are char arrays.
I am not sure if that is the correct way to initialize them in C++. Any suggestions ?
A proper approach in C++ is to use std::string in place of char*.
struct temp
{
std::string person;
std::string address;
int id;
int phone;
}
This change would ensure that the resources for your string are managed automatically.
If you must use C strings as part of a learning exercise, and you wish to initialize them to an empty string (as opposed to a NULL pointer), you can use operator new[], like this:
Data ( )
{
var -> person = new char[1];
var -> person[0] = 0;
var -> address = new char[1];
var -> address[0] = 0;
var.id = 0;
var.phone = 0;
}
If you take this approach, you need to add code that de-allocates the memory once you are done with your var, i.e. something like this:
delete[] var -> person;
delete[] var -> address;
new" or "operator new"? Don't we love it.
std::string, it does not care about the size - it would take as much or as little as is there, and it will change later if you wish to add or remove some characters. It would also free memory at the end.this pointer except to disambiguate the expression. In this case, don't use this-> unless there's also a local variable or a function parameter named var that would "shadow" the member variable var.If you want to set the pointer field to NULL (or nullptr in C++11) try
var -> person = NULL;
If you want to set it to a literal constant string, try something like
var -> person = "John Doe";
(As Paul R commented, make that a std::string)
Better yet, make your struct temp an authentic class so provide constructors and destructors to it. Read about the Rule of three (in C++11, it is becoming the rule of five).
-> operator in my life, and now both you and the TS do it. Did I miss a hip new coding standard somewhere?I would simply set them to NULL. On a side note, I couldn't help but notice you had var-> and var. mixed. If you create an object, it is [.] If you are referencing a pointer to the base object it is [->].
typedef struct TTEMP
{
char* person;
char* address;
int id;
int phone;
}TTemp;
Data ( )
{
TTemp var;
var.person = NULL;
var.address = NULL;
var.id = 0;
var.phone = 0;
..............
}
this-> is not required. However, the most IDEs provide the syntax completion, when you begin to type this->. That's why you'll often see the redundant this in code.
Struct in C++ is (almost) the same as class, but with all members public by default. You can also initialize in a constructor.
struct temp
{
char* person;
char* address;
int id;
int phone;
temp():person(0),address(0),id(0),phone(0){}
}
temp t; // initialized!
If for some reasons you don't want to have a constructor, create a factory function, which will encapsulate the initialization of the members and create the instances only there. This used to be actually the way in C to mimic the constructors.
temp* create_my_temp()
{
temp *t;
//create using malloc or new
//initialize t;
return t;
}
std::string, as nature intended.nullptr(orNULLif pre-C++11)->for some fields and.for others?