How to reduce a switch in a switch statement?

Question

So I'm making a method to create a salutation line based on two people from a database.

There are four parameters: the two names (name1 and name2) and the two genders (gender and gender2).

For every gender combination, I have a kind of different output.

For example: if gender 1 is M (man) and gender 2 is also M, the output should be something like:

Dear Sir name1 and Sir name2,

At this time, my switch looks like this:

switch(gender1){
    case 'M':
        switch(gender2){
            case 'M': printf("Dear Sir %s and Sir %s", name1, name2); break;
            case 'W': printf("Dear Sir %s and Madame %s", name1, name2); break;
            case 'R': ...
        }
        break;
    case 'W':
        switch(gender2){
            case 'M': printf("Dear Madame %s and Sir %s", name1, name2); break
            case 'W': printf("Dear Madame %s and Madame %s", name1, name2); break;
            case 'R': ...
        }
        break;
    case ...etc.
}

Note that I have multiple gender options, like 'R' for "Dear Relation" and some more that I do not have the time to translate.

How can I reduce this double switch statement?

Putting the second switch in a method is not an option because there is also a case where both of the names are the same and then the output should be combined like: "Dear Sir and Madame name1,"

score 32 · Accepted Answer · edited Jul 14 '15 at 13:21

Add the title to the parameters of the printf:

char* title1;
switch(gender1){
    case 'M':
        title1 = "Sir";
        break;
    case 'W':
       title1 = "Madam";
        break;
    case ...etc.
}
char* title2;
switch(gender2){
    case 'M':
        title2 = "Sir";
        break;
    case 'W':
       title2 = "Madam";
        break;
    case ...etc.
}
printf("Dear %s %s and %s %s", title1, name1, title2, name2);

you can extract the switch to its own function for re-usability and compactness.

score 18 · Answer 2 · answered Jul 14 '15 at 12:18

Radical solution: Let the user specify their own title (from a predefined list that you provide).

Your solution (as viewed through English eyes) only appears to cater for Lords ("Sir") and ladies; most men would be addressed as "Mr", most women as either "Miss", "Mrs" or "Ms", depending on their marital status and personal opinions. Then there's a whole slew of other honorifics based on professional standings - "Doctors", "Professors", "Reverends" and even, if you're feeling really optimistic about your site, "Holiness"!

Simpler solution: You need a [single] function to translate "gender" into an honorific. Code it once and call it for both people:

printf("Dear %s %s and %s %s" 
   , getTitle( gender1 ), name1 
   , getTitle( gender2 ), name2 
   ) ;

score 9 · Answer 3 · answered Jul 14 '15 at 16:10

Titles really belong in the database, but you stated you have no control over this. You have not specified a language tag but the syntax is in the C family, so this will be pseudocode that is almost C++:

map<string, string> titles;
titles.emplace("M", "Sir");
titles.emplace("F", "Madam");

cout << "Dear " << titles[gender1] << " " << name1 << " and "
     << titles[gender2] << " " << name2 << endl;

The benefit to this is you bury the selection logic in a data structure rather than a code structure: this is similar to delegating to the database, and is more flexible. If you keep that map as a static constant somewhere, you can almost use it like a database: it becomes a single structure to update which can be used in many places in the code without needing to write more code.

score 3 · Answer 4 · edited Apr 12 '17 at 07:31

ratchet freak's answer is quite a good idea if the sentences are all the same pattern, but with two insets, one each only dependent on gender1 respective gender2.

Phil W.'s answer is probably the most flexible answer as it allows explicit control over the greeting, though he's quite correct it's a radical change. You might not have the data in that form.

Kilian Foth's answer is probably the best for the question as asked, though he depends on switching on a string, which might not be possible or is likely more expensive at least.

A refinement on Kilian's answer is computing a single value from both inputs, and switching on that:

// Using a macro in C for readability. C++ would use a constexpr function
#define COMBINE(a, b) ((a<<CHAR_BIT)+b)

switch( COMBINE(gender1, gender2)) {
  case COMBINE('M', 'M'): 
    print "Dear Sirs";
    break;
  case COMBINE('M', 'F'): 
  case COMBINE('F', 'M'): 
    print "Dear Sir and Madam";
    break;
  ...
#undef COMBINE

Of course, as you are getting all four inputs (2 names and 2 genders) from a database, adding another table and joining on that to get the proper salutation is probably more flexible and maybe easier than the above.

score 2 · Answer 5 · answered Jul 14 '15 at 09:11

If your language allows you to do it, you can write

switch(gender1+gender2) {
  case "MM": 
    print "Dear Sirs";
    break;
  case "MF": 
  case "FM":
    print "Dear Sir and Madam";
    break;
  ...

It's not necessarily better than your version, since there's still duplication, but it does avoid the nested switch.

score 0 · Answer 6 · answered Jul 15 '15 at 14:52

You would typically want UI strings like this to be pulled in from a string table instead of being hard-coded in the source code, for localization and ease of updating. So the approach I would take would be to use the inputs to build a lookup key, so something like:

var lookupKey = "SALUTATION_" + gender1 + "_" + gender2;
var format = GetLocalizedString(lookupKey);
printf(format, name1, name2);

The other suggestions about letting users select their own titles is valid, if you have the opportunity to get that information. I would still use a string table lookup in the solution.

How to reduce a switch in a switch statement?

6 Answers6