implementing retry in while loop - c++

Question

I am trying to implement a retry in the while loop. I want to retry 5 times and if the flag becomes true.
bool flag = false;
unsigned int count = 5;
while(!flag && count > 0) {
DataOperation opt = DataUser::Insert(data_point);
if(opt == DataOperation::DataEnum) {
UserPointData exist = DataUser::FindUser(data_point->user_id());
if(exist) {
exist->attributeData.put(key, value, len_value, client_id, last_modified_date);
flag = true;
}
} else {
// insert in data_point
data_point->attributeData.put(key, value, len_value, client_id, last_modified_date);
flag = true;
}
count--;
}
So if flag becomes true, then I will exit out of the loop
Second case, if flag is false for 5 times, then I will exit out of the loop as well.
Does this look right what I am doing?

Answer 1

Just like #Borgleader pointed out, the flag variable is unnecessary. You can stick with a break instruction and check after the loop if the count is still bigger than zero. If so, means your task succeeded.
unsigned int count = 5;
while(count > 0) {
DataOperation opt = DataUser::Insert(data_point);
if(opt == DataOperation::DataEnum) {
UserPointData exist = DataUser::FindUser(data_point->user_id());
if(exist) {
exist->attributeData.put(key, value, len_value, client_id, last_modified_date);
break; // success.
}
} else {
// insert in data_point
data_point->attributeData.put(key, value, len_value, client_id, last_modified_date);
break; // success.
}
count--;
}
if (count > 0) { /* succeeded within 5 tries. */ }

Answer 2

What you are doing seems fine but possibly more complicated than it needs to be.
For example you don't need to set a flag to exit you can simply call break;.
Here is a pattern I sometimes use that maybe simpler:
bool succeed_at_doing_stuff()
{
std::cout << "trying" << '\n';
return false;
}
int main()
{
int retries = 3;
while(retries--) // will exit when retries == 0, retries then becomes -1
{
if(succeed_at_doing_stuff())
break; // no need to set a flag
// take alternative action
}
if(retries < 0) // retries was decremented after last check
{
std::cerr << "error: gave up - too many retries" << std::endl;
return 1;
}
}

Answer 3

If you will use count variable only for that purpose, I suggest you to use a for loop so count will not be visible and memory of it will be reclaimed after exiting the scope of the loop. And use break statement to immediately exit the loop.
for(auto count = 0; count<5; ++count) {
DataOperation opt = DataUser::Insert(data_point);
if(opt == DataOperation::DataEnum) {
UserPointData exist = DataUser::FindUser(data_point->user_id());
if(exist) {
exist->attributeData.put(key, value, len_value, client_id, last_modified_date);
break;
}
} else {
// insert in data_point
data_point->attributeData.put(key, value, len_value, client_id, last_modified_date);
break;
}
}

Answer 4

The only change I would make is
if(opt == DataOperation::DataEnum) {
UserPointData exist = DataUser::FindUser(data_point->user_id());
if(exist) {
exist->attributeData.put(key, value, len_value, client_id, last_modified_date);
flag = true;
} else {
count--;
}
I am not crazy about you setting count to 5 then counting down, as it is more obvious if you increment until you reach 5, but this will work.
You may want to break instead of setting flag, unless you are planning on using flag to differentiate between finding a match or exiting due to the conditional.