Array problem

[Tommy Lang]

Hi!

I have aa array with pointers to the class(object) Person that I
created
( Person *ptr[10]; ). From class person there are two derived classes,
student and employee. I can add and remove objects of these types in
my array. Now I want to be able to search for a specific object of my
choice based on the persons name. How do I do that?? I need help.

So far this is what I've come up with...

//The class Personlist contains the Person *ptr[10], and functions
//to add/remove objects.
bool Personlist::fin d(char* name, int & position)
{
bool result = true;
int i = 0;
position = -1;

while(i<number_ of_elements)//number_of elements is number of
//objects in array
{
//The Person class have a variable called m_name.
//How can I reach it from here and compare it to what
//name is sent into this function? For now I just want
to
//return true or false (and reference to position).

i++;
}

if(position == -1)
result = false;

return result;

}


Thanks,
Tommy

[Patrik Stellmann]

Re: Array problem

<snip>[color=blue]
> //The class Personlist contains the Person *ptr[10], and functions
> //to add/remove objects.
> bool Personlist::fin d(char* name, int & position)[/color]
You should use 'const char* name' since you're not goint to modify that
string! Even better would be to use std::string instead of char-arrays...[color=blue]
> {
> bool result = true;
> int i = 0;
> position = -1;
>
> while(i<number_ of_elements)//number_of elements is number of
> //objects in array[/color]
Hint: You could already leave the loop when you have found the name in
the list and, thus, position is no more -1.[color=blue]
> {
> //The Person class have a variable called m_name.
> //How can I reach it from here and compare it to what
> //name is sent into this function? For now I just want
> to
> //return true or false (and reference to position).[/color]
The function to compare to char-arrays is strcmp which returns 0 if both
are equal. If you'd use std::string you can simply use the operator==.[color=blue]
>
> i++;
> }
>
> if(position == -1)
> result = false;
>
> return result;
>
> }[/color]
You should also consider using std::map instead of an array to store the
Person-pointers since it is much more flexible and more comfortable to
use...

[Sharad Kala]

Re: Array problem


"Tommy Lang" <mums_se@yahoo. se> wrote in message
news:78dde37d.0 402250037.5a1a6 486@posting.goo gle.com...[color=blue]
> Hi!
>
> I have aa array with pointers to the class(object) Person that I
> created
> ( Person *ptr[10]; ). From class person there are two derived classes,
> student and employee. I can add and remove objects of these types in
> my array. Now I want to be able to search for a specific object of my
> choice based on the persons name. How do I do that?? I need help.
>
> So far this is what I've come up with...
>
> //The class Personlist contains the Person *ptr[10], and functions
> //to add/remove objects.
> bool Personlist::fin d(char* name, int & position)
> {
> bool result = true;
> int i = 0;
> position = -1;
>
> while(i<number_ of_elements)//number_of elements is number of
> //objects in array
> {
> //The Person class have a variable called m_name.
> //How can I reach it from here and compare it to what
> //name is sent into this function? For now I just want
> to[/color]
Ibelieve Personlist ia nother class different from person.
Add a public member function to your Person class.
It should return you the m_name varaible.
Then use strcmp to compare the values in this function.
Even better and safe is to use std::string.

-Sharad

[John Harrison]

Re: Array problem


"Tommy Lang" <mums_se@yahoo. se> wrote in message
news:78dde37d.0 402250037.5a1a6 486@posting.goo gle.com...[color=blue]
> Hi!
>
> I have aa array with pointers to the class(object) Person that I
> created
> ( Person *ptr[10]; ). From class person there are two derived classes,
> student and employee. I can add and remove objects of these types in
> my array. Now I want to be able to search for a specific object of my
> choice based on the persons name. How do I do that?? I need help.
>
> So far this is what I've come up with...
>
> //The class Personlist contains the Person *ptr[10], and functions
> //to add/remove objects.
> bool Personlist::fin d(char* name, int & position)[/color]

That should be

bool Personlist::fin d(const char* name, int & position) const

const correctness is important in C++.
[color=blue]
> {
> bool result = true;
> int i = 0;
> position = -1;
>
> while(i<number_ of_elements)//number_of elements is number of
> //objects in array
> {
> //The Person class have a variable called m_name.
> //How can I reach it from here and compare it to what
> //name is sent into this function? For now I just want
> to
> //return true or false (and reference to position).[/color]

Are you using a character array or a string to store the name? You should be
using a string but many newbies don't because they aren't taught right. I'm
going to assume a character array.

You should have something like this in your Person class

class Person
{
public:
...
const char* get_name() const { return m_name; }
...
private:
...
char m_name[99]; // name is a character array
...
};

Then in your loop you use strcmp to compare the passed in name with the
person name.

if (strcmp(ptr[i]->get_name, name) == 0)
// names are the same
else
// names are different

john

[Karl Heinz Buchegger]

Re: Array problem

John Harrison wrote:[color=blue]
>
>
> class Person
> {
> public:
> ...
> const char* get_name() const { return m_name; }
> ...
> private:
> ...
> char m_name[99]; // name is a character array
> ...
> };
>
> Then in your loop you use strcmp to compare the passed in name with the
> person name.
>
> if (strcmp(ptr[i]->get_name, name) == 0)[/color]

Typo:
if (strcmp(ptr[i]->get_name(), name) == 0)


--
Karl Heinz Buchegger
kbuchegg@gascad .at

[John Harrison]

Re: Array problem

>[color=blue]
> if (strcmp(ptr[i]->get_name, name) == 0)
>[/color]

Sorry, should be

if (strcmp(ptr[i]->get_name(), name) == 0)

john