C++/Language/try catch

Catch all types of exceptions

<source lang="cpp">

1. include <iostream>

using namespace std; void XHandler(int test){

  try {
     if(test==0) throw test;
     if(test==1) throw "a";
     if(test==2) throw 123.23;
  }catch(...){
     cout << "Caught one." << endl;
  }

} int main(void){

  cout << "Start: " << endl;
  XHandler(0);
  XHandler(1);
  XHandler(2);
  cout << "End";

}

 </source>

Catch By Non Const Reference

<source lang="cpp">

1. include <fstream>
2. include <iostream>
3. include <vector>
4. include <string>
5. include <exception>

using namespace std; void readIntegerFile(const string& fileName, vector<int>& dest) {

 ifstream istr;
 int temp;
 istr.open(fileName.c_str());
 if (istr.fail()) {
   throw exception();
 }
 while (istr >> temp) {
   dest.push_back(temp);
 }

} int main(int argc, char** argv) {

 vector<int> myInts;
 const string fileName = "IntegerFile.txt";
 try {
   readIntegerFile(fileName, myInts);
 } catch (exception& e) {
   cerr << "Unable to open file " << fileName << endl;
   exit (1);
 }
 for (size_t i = 0; i < myInts.size(); i++) {
   cout << myInts[i] << " ";
 }
 cout << endl;
 return (0);

}

 </source>

Catch By Value

<source lang="cpp">

1. include <fstream>
2. include <iostream>
3. include <vector>
4. include <string>
5. include <exception>

using namespace std; void readIntegerFile(const string& fileName, vector<int>& dest) {

 ifstream istr;
 int temp;
 istr.open(fileName.c_str());
 if (istr.fail()) {
   throw exception();
 }
 while (istr >> temp) {
   dest.push_back(temp);
 }

} int main(int argc, char** argv) {

 vector<int> myInts;
 const string fileName = "IntegerFile.txt";
 try {
   readIntegerFile(fileName, myInts);
 } catch (exception e) {
   cerr << "Unable to open file " << fileName << endl;
   exit (1);
 }
 for (size_t i = 0; i < myInts.size(); i++) {
   cout << myInts[i] << " ";
 }
 cout << endl;
 return (0);

}

 </source>

Catch char pointer type exception

<source lang="cpp">

1. include <iostream>

using namespace std; void XHandler(void)

{
  try {
     throw "hello";
   }
  catch(char *) {
     cout << "Caught char * inside XHandler." << endl;
     throw;
   }
}

int main(void)

{
  cout << "Start: " << endl;
  try {
     XHandler();
   }
  catch(char *) 
  {
     cout << "Caught char * inside main." << endl;
   }
  cout << "End";
  
}
 
   
 </source>

Catch different types of exception

<source lang="cpp">

1. include <iostream>

using namespace std; void XHandler(int test) throw(){

  if(test==0)
    throw test;
  if(test==1)
    throw "a";
  if(test==2)
    throw 123.23;

} int main(void){

  cout << "Start: " << endl;
  try{
     XHandler(0);                  // try passing 1 and 2 for different responses
  }catch(int i){
     cout << "Caught an integer." << endl;
  }catch(char c){
     cout << "Caught a character." << endl;
  }catch(double d){
     cout << "Caught a double." << endl;
  }
  cout << "End";

}

 </source>

Catch exception from a function

<source lang="cpp">

1. include <iostream>

using namespace std; void XHandler(int test) throw(int, char, double){

  if(test==0) throw test;
  if(test==1) throw "a";
  if(test==2) throw 123.23;

} int main(void){

  cout << "Start: " << endl;
  try {
     XHandler(0);                  // try passing 1 and 2 for different responses
   }
  catch(int i) {
     cout << "Caught an integer." << endl;
   }
  catch(char c) {
     cout << "Caught a character." << endl;
   }
  catch(double d) {
     cout << "Caught a double." << endl;
   }
  cout << "End";
 
}
 
   
 </source>

Catch int type exception in a function

<source lang="cpp">

1. include <iostream>

using namespace std; void XHandler(int test){

  try {
     if(test) throw test;
  }catch(int i){
     cout << "Caught exception #: " << i << endl;
  }

} int main(void){

  cout << "Start: " << endl;
  XHandler(1);
  XHandler(2);
  XHandler(0);
  XHandler(3);
  cout << "End";

}

 </source>

Catch more than one type of exceptions

<source lang="cpp">

1. include <iostream>

using namespace std; void XHandler(int test){

  try {
     if(test==0) throw test;
     if(test==1) throw "a";
     if(test==2) throw 123.23;
  }catch(int i){
     cout << "Caught an integer." << endl;
  }catch(...){
     cout << "Caught one." << endl;
  }

} int main(void){

  cout << "Start: " << endl;
  XHandler(0);
  XHandler(1);
  XHandler(2);
  cout << "End";

}

 </source>

Checking for a divide-by-zero exception.

<source lang="cpp">

1. include <iostream>

using std::cout; using std::cin; using std::endl; class DivideByZeroException { public:

  DivideByZeroException()
     : message( "attempted to divide by zero" ) { }
  const char *what() const { return message; }

private:

  const char *message;

}; double quotient( int numerator, int denominator ) {

  if ( denominator == 0 )
     throw DivideByZeroException();
  return static_cast< double > ( numerator ) / denominator;

} int main() {

  int number1, number2;
  double result;
  cout << "Enter two integers (end-of-file to end): ";
  while ( cin >> number1 >> number2 ) {
     try {
        result = quotient( number1, number2 );
        cout << "The quotient is: " << result << endl;
     }
     catch ( DivideByZeroException ex ) { 
        cout << "Exception occurred: " << ex.what() << "\n";
     }
     cout << "\nEnter two integers (end-of-file to end): ";
  } 
  cout << endl;
  return 0;

}

 </source>

Code block of try...catch

<source lang="cpp">

1. include <iostream>

using namespace std; int main(void){

  cout << "Start" << endl;
  try {
     cout << "Inside try block." << endl;
     cout << "Still inside try block." << endl;
  }catch(int i){
     cout << "Caught an exception--value is: " << endl;
     cout << i << endl;
  }
  cout << "End";

}

 </source>

Finally catch all Exceptions

<source lang="cpp">

1. include <iostream>
2. include <stdlib.h>

using namespace std; void foo() {

  int  i, j;
  i = 14;
  j = 15;

} void call_foo() {

  int  k;
  k  = 12;
  foo();

} void call_foo2() {

  double  x = 1.3;
  throw (x);

} int main() {

  try {
     call_foo();  //foo exitted with i and j destroyed
     call_foo2();
  }
  catch (char* message)
  {
     cerr << message << endl;
     exit(1);
  }
  catch(int n) { cout << "\ncaught it " << n << endl; }
  catch( ... )      
  {
     cerr << "THAT"S ALL FOLKS." << endl;
     abort();
  }

}

 </source>

Localize a try/catch to a function.

<source lang="cpp">

1. include <iostream>

using namespace std;

void myFunction(int test) {

 try{
   if( test ) 
      throw test;
 }catch(int i) {
   cout << "Caught Exception #: " << i << "\n";
 }

} int main() {

 cout << "Start\n";
 myFunction(1);
 myFunction(2);
 myFunction(0);
 myFunction(3);
 cout << "End";
 return 0;

}

 </source>

Use multiple catch statements.

<source lang="cpp">

1. include <iostream>

using namespace std;

void myFunction(int test) {

 try{ 
   if(test) 
      throw test; // throw int 
   else 
      throw "Value is zero"; // throw char * 
 } 
 catch(int i) { 
   cout << "Caught One!  Ex. #: " << i << "\n"; 
 } 
 catch(char *str) { 
   cout << "Caught a string: "; 
   cout << str << "\n"; 
 } 

}

int main() {

 cout << "start\n"; 

 myFunction(1); 
 myFunction(2); 
 myFunction(0); 
 myFunction(3); 

 cout << "end"; 

 return 0; 

}

 </source>

Using Multiple catch Statements

<source lang="cpp">

1. include <iostream>

using namespace std; void myFunction(int test) {

 try{
   if(test) throw test;
   else throw "Value is zero";
 }
 catch(int i) {
   cout << "Caught Exception #: " << i << "\n";
 }
 catch(const char *str) {
   cout << "Caught a string: ";
   cout << str << "\n";
 }

} int main() {

 cout << "Start\n";
 myFunction(1);
 myFunction(2);
 myFunction(0);
 myFunction(3);
 cout << "End";
 return 0;

}

 </source>