I am writing a code in which some process is done in if block. But if result of process is not aa expected, I want to execute else block.
if(condition1)
{
// Some processing
if(another condition)
//Do some task;
else
//Execute else of outer block;
}
else
{
}
You can do this by rewriting your if condition:
if (condition1) {
// Some processing
}
if (condition1 && another condition) {
// Do some task;
} else {
// Execute else of outer block;
}
condition1 it's by far the clearest of the answers presented thus far, including mine. It's there something missing?
While the admonitions against such construction are certainly worth considering in earnest, it is possible to do what you ask in a structured way using a switch statement with a fallthru.
e.g.:
switch(condition1)
{
case true:
// some processing
if(condition2)
{
// Do some task;
break;
}
[[fallthrough]]; // or just comment: fallthru if not using c++17
case false:
// execute else of outer block;
}
You can rely on the short-circuiting property of && and the expression separator operator , and write
if (condition1 && (some processing, another condition)){
// Do some task
} else {
// The outer block
}
Here some processing and another condition are only evaluated if condition1 is true.
This does have the advantage that condition1 is only evaluated once which is useful if it has side-effects.
It's also succinct but is not really feasible if some processing is not a simple expression (it works nicely if it's a function call).
some processing is brief or a function call, this solution can work well.Another technique to add to existing answers:
bool skip_X = false;
if (condition1)
{
// Some processing
if (another condition)
{
//Do some task;
skip_X = true;
}
}
if (!skip_X)
....
This avoids evaluating condition1 twice, which can be problematic if it has side effects or values in the expression could be changed by processing inside the if or even in another thread.
That said...
How can I jump from if block to else block without using goto?
The language has goto for a reason, and - just like people who say "how can my constructor report an error without throwing an exception" - by artificially restricting yourself from using the language feature clearly best suited to your need you create worse code.
if,else ifandelse? Of course this does not mean you should not put it in a function as suggested.