Question

I have declared a map like this

map<long long, list<SoundInfo *> > m_soundListMap;

and I also have this function

void addSoundInfo(long long deviceId, SoundInfo * info)

I am trying to add sound info associate with the device id as the key into the map. In this function, I assumed that a key and value pair has been added to the map. So I can retrieve the list of the sound info and add incoming sound info to the back of the list.

I want to catch an exception for the case that the map doesn’t have the key then I can create the key and value pair and insert into the map.

How do I catch this exception in C++?

Thanks in advance…

Answer 1

What is going to happen if I try to get the list and the map doesn’t have the key?

Depends on how you try to get the item.

list<SoundInfo*>& info_list = m_soundListMap[55];

Will create an empty list, insert it into the map and return that when the key doesn’t exist yet.

typedef map<long long, list<SoundInfo *> >::iterator iterator;
iterator iter = m_soundListMap.find(55);

Will return an iterator to the pair that holds both the key and the value, or will be map::end() if the key doesn’t exist. iter->second will be your list<SoundInfo*>.