switch()
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Dang, I just found that I can't use strings in a switch statement. What can I do to work around this? I tried .c_str() but that doesn't work, presumably because that changes a string to a char* and not an int, but I thought I'd try it anyway. What do I do for this? If there isn't a simple solution, I'll just use a bunch of ifs and else ifs, but now I'm curious and wish to know how to get it to work. Thanks!
-Servant of the Lord
You can create a std::map<std::string, something> to map strings to integers that you can switch on or function objects that you can invoke.
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Quote:Original post by SiCrane
You can create a std::map<std::string, something> to map strings to integers that you can switch on or function objects that you can invoke.
How do I do that? My string is called 'Input' so I would go:
std::map<Input, N_Input>switch(N_Input){ case "north" || "n": ...And do I need to include special headers, or is it in iostream?
He's saying have a map that converts "north" to ID_DIRECTION_NORTH or something like that which is a number. Then switch on the number.
If there are only a few possible strings I would just use a bunch of if/else statements. If there are a large number you could do something like map a string to a function pointer but that's more complicated.
If there are only a few possible strings I would just use a bunch of if/else statements. If there are a large number you could do something like map a string to a function pointer but that's more complicated.
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Quote:Original post by Anon Mike
He's saying have a map that converts "north" to ID_DIRECTION_NORTH or something like that which is a number. Then switch on the number.
If there are only a few possible strings I would just use a bunch of if/else statements. If there are a large number you could do something like map a string to a function pointer but that's more complicated.
I currently have 37 possible strings, so I'll try and map them. I still don't quite understand how this is done though, so could someone show me how to or point me to a small tutorial?
Something like this:
Or something like that. There may be a better way to do it, I'm not sure. It's been ages since I used std::map...
enum Direction{ North, South, West, East};std::map<Direction, std::string> stringMap;// In init code:stringMap[North] = "North";stringMap[South] = "South";stringMap[West] = "West";stringMap[East] = "East";// When you check the values:std::map<Direction, std::string>::iterator it = stringMap.find(input);if(it == stringMap.end()){ // Invalid input, can't find this string in the map (like the "default" case statement)}switch(it.first){ case North: break; case South: break; case West: break; case East: break;}Or something like that. There may be a better way to do it, I'm not sure. It's been ages since I used std::map...
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Thanks. That seems rather chunky for what seems like a simple thing. Someone should create a varation of switch which acepts most variables. I'll mess around with what you've given me though, and see if I can understand it and make switching simpler.
Thanks for all your help everyone.
Thanks for all your help everyone.
I'd go the other way, and map strings to directionids, not the other way around.
Note: you'll need to either come up with a case insensitive string compare, or else ensure that your strings are first converted to the proper case.
enum{ NORTH, EAST, SOUTH, WEST};std::map<std::string,int> the_map;the_map["NORTH"]=NORTH;the_map["N"]=NORTH;the_map["EAST"]=EAST;the_map["E"]=EAST;the_map["SOUTH"]=SOUTH;the_map["S"]=SOUTH;the_map["WEST"]=WEST;the_map["W"]=WEST;std::string command = getCommand();std::map<std::string,int>::iterator iter = the_map.find(command);if(iter != the_map.end() ){ switch(iter->second){ case NORTH: //go north break; case EAST: //go east break; case SOUTH: //go south break; case WEST: //go west break; default: //unknown command } }Note: you'll need to either come up with a case insensitive string compare, or else ensure that your strings are first converted to the proper case.
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