In practice, the string series in c ++ -- use string in the switch statement (c ++ does C #, and break in the switch is still very powerful)

In practice, the string series in c ++ -- use string in the switch statement (c ++ does C #, and break in the switch is still very powerful)

How many times have you written this as a C ++ programmer out of habit or helplessness:

if (!strcmp(pszValue, "Value X"))    DoThis();else if (!strcmp(pszValue, "Value Y"))    DoThat();else if (!strcmp(pszValue, "Value Z"))    DoSomethingElse();else    DontKnowWhatToDo();

You have asked for thousands of times how nice it would be to use a switch at this time?

switch(strValue){case "Value X":    DoThis();    break;case "Value Y":    DoThat();    break;case "Value Z";    DoSomethingElse();    break;default:    DontKnowWhatToDo();    break;

The above code is legal in C Sharp, but as a C ++ programmer, you can only be helpless and helpless.

Here is the desire to use enum and std: map!

#include#include 
   
    #include 
    
     // Value-Defintions of the different String valuesstatic enum StringValue { evNotDefined,                           evStringValue1,                           evStringValue2,                           evStringValue3,                           evEnd };// Map to associate the strings with the enum valuesstatic std::map
     
       s_mapStringValues;// User inputstatic char szInput[_MAX_PATH];// Intializationstatic void Initialize();int main(int argc, char* argv[]){  // Init the string map  Initialize();  // Loop until the user stops the program  while(1)  {    // Get the user's input    cout << "Please enter a string (end to terminate): ";    cout.flush();    cin.getline(szInput, _MAX_PATH);    // Switch on the value    switch(s_mapStringValues[szInput])    {      case evStringValue1:        cout << "Detected the first valid string." << endl;        break;      case evStringValue2:        cout << "Detected the second valid string." << endl;        break;      case evStringValue3:        cout << "Detected the third valid string." << endl;        break;      case evEnd:        cout << "Detected program end command. "             << "Programm will be stopped." << endl;        return(0);      default:        cout << "'" << szInput   << "' is an invalid string. s_mapStringValues now contains "             << s_mapStringValues.size()              << " entries." << endl;        break;    }  }  return 0;}void Initialize(){  s_mapStringValues["First Value"] = evStringValue1;  s_mapStringValues["Second Value"] = evStringValue2;  s_mapStringValues["Third Value"] = evStringValue3;  s_mapStringValues["end"] = evEnd;  cout << "s_mapStringValues contains "        << s_mapStringValues.size()        << " entries." << endl;}
     
    
   

Here is a particularly important technique, that is, why is the first enumeration set to evNotDefined?

First, we need to clarify the role of std: map: operator:
1. Set the value of a key
2. At this time, you must note that, if it does not exist, it will be inserted.

That is, for s_mapStringValues in the program, if szInput is new, it will be inserted.
And the value is 0 by default.
If the first item of enumeration is evStringValue1, any unknown string value will lead to a valid switch case. That's why we did this.

========================================================== ======================================
There is also a small question to discuss, that is, the return Statement in the switch statement is powerful or break is powerful:
Code:

Switch (s_mapStringValues [szInput]) {case evStringValue1: cout <"Detected the first valid string." <endl; return 0; // will break be executed? Break; case evStringValue2: cout <"Detected the second valid string. "<endl; break; case evStringValue3: cout <" Detected the third valid string. "<endl; break; case evEnd: cout <" Detected program end command. "<" Programm will be stopped. "<endl; return (0); default: cout <" '"<szInput <"' is an invalid string. s_mapStringValues now contains "<s_mapStringValues.size () <" entries. "<endl; break ;}

Test. On the surface, return won't break.