Without encapsulation, external code can assign illegal or corrupted values directly to member variables. Encapsulation routes all modifications through validated member methods:
WITHOUT ENCAPSULATION:
External Code ──(Direct Write: balance = -50000)──► Unprotected Struct (Invalid State!)
WITH ENCAPSULATION:
External Code ──► withdraw(50000) ──► [Invariant Validation] ──► Denied / Approved#include <iostream>
#include <stdexcept>
class Thermostat {
private:
double currentTemperatureC; // Valid range: -20.0 to 60.0 C
public:
explicit Thermostat(double initialTemp = 20.0) {
setTemperature(initialTemp);
}
void setTemperature(double temp) {
if (temp < -20.0 || temp > 60.0) {
std::cout << "[Error] Temperature " << temp << "C is out of safe range [-20, 60]!\n";
return;
}
currentTemperatureC = temp;
std::cout << "[Thermostat] Target set to " << currentTemperatureC << " C\n";
}
double getTemperature() const {
return currentTemperatureC;
}
};
int main() {
Thermostat thermo(22.5);
thermo.setTemperature(26.0); // Valid
thermo.setTemperature(150.0); // Rejected by invariant validation
std::cout << "Current safe temperature: " << thermo.getTemperature() << " C\n";
return 0;
}