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ostringstream and istringstream (An easy question).

I am trying to use a ostringstream object from sstream library file. I am using << to perform a formatted output operation. Using ostr<<(arg) operation will cause ostr to store the argument as a string. Then I use ostr.str() function to read the arg into a string object. Now my problem is I want to clear whatever has been stored in ostr object and pass another arguement to it. How can I do it? Reply asap.Thanks.

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jhshukla

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pb_india

use:

ostr.flush();

b_vishwajit

ASKER

I am gonnna try that. I have another doubt: If I have an object declared as Object *obj in my main program then how would I pass this object to function to called print() to create and initialize the object and then print its data members. Reply. Thanks.

b_vishwajit

ASKER

ostr.flush() does not work. In fact I tried ostr.flush() before posting my question on this forum. But seekp(0) does work. Thanks jhshukla. Now can some one clarify my other doubt of passing objects to functions.

jhshukla

Object *obj;
print(&obj);

void print(Object **pObj){
*pObj = new Object();
(*pObj)->field1 = some_value1;
...
cout
<< (*pObj)->field1 << endl
<< (*pObj)->field2 << endl
......
<< (*pObj)->fieldn << endl;
}

if you will be printing the contents quite often then you should consider overloading the << operator. gtg to class. will give details after coming back.

happy programming.
jaydutt

b_vishwajit

ASKER

Thank you again for replying. I did it the following way: (took me one hour to figure it out since I am newbie to c++)
      Object *obj;
      void print(Object*);//dateObj=new Date("10","11","1983");
      print(dateObj);

print(Object *obj)
{
obj=new Object();
cout<<obj->toString()<<endl;

}

It works. Which one do you think is better and why? Thanks.

b_vishwajit

ASKER

does seekp(arg); work for istringstream too? I have'nt tried it yet. Or do I have to use seekg(); Thanks.

itsmeandnobodyelse

That works also:

ostringstream oss;
string s;
oss << "A string";
cout << oss.str() << endl;
oss.str(""); // make string empty
oss << "Another string";
cout << oss.str() << endl;

Regards, Alex

P.S. Should work for istringstream too.

b_vishwajit

ASKER

Thank you Alex. I will try your suggestion for istringstream as seekp() works for ostringstream.You said:
>>That works also:

Whats "that"? U mean seekg();?

itsmeandnobodyelse

>> how would I pass this object to function to called print()

void print(Object*& pObj)
{
pObj = new Object(arg1, arg2, arg3); // init your data members in the constructor
cout << *pObj;
}

For this you need ostream::operator<< like that:

ostream& operator<< (ostream& os, const Object& obj) const
{
os << obj.getFirstMember() << " " << obj.getSecondMember() << .... << endl;
}

Make a forward declaration in the class header and implementation either as inline in the header too or in the cpp file of class Object.

Regards, Alex

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itsmeandnobodyelse

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