enumerations: Possible to get the "key" string?

[Georg J. Stach]

Hello,

taken I've declared an enumeration like this:

enum Color{ red,green,blue };

The internal representation of Color is of type integer and it's no problem
to print out their values.

But is it possible to get their string representing value _without_ having a
switch like this?

switch (Color) {
case (red):
string str("red");
.
.
.
}



Thanks for replies
Georg

 

[=?ISO-8859-1?Q?Andr=E9_Kempe?=]

Hello,

taken I've declared an enumeration like this:

enum Color{ red,green,blue };

The internal representation of Color is of type integer and it's no problem
to print out their values.

But is it possible to get their string representing value _without_ having a
switch like this?

switch (Color) {
case (red):
string str("red");
.
.
.
}

const char* str_table[ ] = { "red" , "green" , "blue" };
string str = str_table[ color ];

 

[Bob Hairgrove]

Hello,

taken I've declared an enumeration like this:

enum Color{ red,green,blue };

The internal representation of Color is of type integer and it's no problem
to print out their values.

But is it possible to get their string representing value _without_ having a
switch like this?

switch (Color) {
case (red):
string str("red");
.
.
.
}

There is no built-in way of doing this. One way would be to store the
strings in a std::map<Color,std::string>, then you could use the map's
find() function to retrieve the string. Alternatively, since you don't
assign values to the enumeration items yourself, the enum value is
equivalent to a sequential index. In that case you could also use a
vector<string> and use the enum value directly as an index into the
vector.

 

[Bob Hairgrove]

Hello,

taken I've declared an enumeration like this:

enum Color{ red,green,blue };

The internal representation of Color is of type integer and it's no problem
to print out their values.

But is it possible to get their string representing value _without_ having a
switch like this?

switch (Color) {
case (red):
string str("red");
.
.
.
}

const char* str_table[ ] = { "red" , "green" , "blue" };
string str = str_table[ color ];

Of course, this will not work if the enum values are not sequential
beginning with 0 (i.e. automatically generated). But it would work in
this special case.

 

[Greg]

There is no built-in way of doing this. One way would be to store the
strings in a std::map<Color,std::string>, then you could use the map's
find() function to retrieve the string. Alternatively, since you don't
assign values to the enumeration items yourself, the enum value is
equivalent to a sequential index. In that case you could also use a
vector<string> and use the enum value directly as an index into the
vector.

A std::map also supports indexing of its values with its keys:

#include <map>
#include <iostream>

enum Color { red, green, blue };

int main()
{
std::map< Color, std::string > colorMap;

colorMap[ red ] = "red";
colorMap[ blue ] = "blue";
colorMap[ green ] = "green";

std::cout << colorMap[ red ]; // prints red
std::cout << colorMap[ blue ]; // prints blue
...
}

Personally, I find the indexing more readable than calls to map::
find().

Greg

 

[Georg J. Stach]

enum Color { red, green, blue };

int main()
{
std::map< Color, std::string > colorMap;

colorMap[ red ]  = "red";
colorMap[ blue ] = "blue";
colorMap[ green ] = "green";
...
}

Thanks Greg and all who have also replied,

I suppose for my application this is the most robust and efficient solution,
as I'm able to sort the map and do some other operations on it.

 

[Greg Comeau]

taken I've declared an enumeration like this:

enum Color{ red,green,blue };

The internal representation of Color is of type integer and it's no problem
to print out their values.

But is it possible to get their string representing value _without_ having a
switch like this?

switch (Color) {
case (red):
string str("red");
.
.
.
}

Check out http://www.comeaucomputing.com/techtalk/#enumtostring