Exceptions

Validation Errors

Validation functions can throw when an input is outside the range the program accepts.

validation Throwing from validation keeps the normal path simple and sends invalid inputs to a handler.

Validation Errors

score
validation_errors.cpp
Replay: real traced execution (multi-file project)
#include <iostream>
#include <stdexcept>

void validateScore(int score) {
    if (score < 0 || score > 100) {
        throw std::out_of_range("score");
    }
}

int main() {
    int score = 85;

    try {
        validateScore(score);
        std::cout << "score=" << score << std::endl;
        std::cout << "valid=1" << std::endl;
    } catch (const std::out_of_range& error) {
        std::cout << "score=" << score << std::endl;
        std::cout << "valid=0" << std::endl;
    }

    return 0;
}

#include <iostream>
#include <stdexcept>

void validateScore(int score) {
    if (score < 0 || score > 100) {
        throw std::out_of_range("score");
    }
}

int main() {
    int score = -5;

    try {
        validateScore(score);
        std::cout << "score=" << score << std::endl;
        std::cout << "valid=1" << std::endl;
    } catch (const std::out_of_range& error) {
        std::cout << "score=" << score << std::endl;
        std::cout << "valid=0" << std::endl;
    }

    return 0;
}

#include <iostream>
#include <stdexcept>

void validateScore(int score) {
    if (score < 0 || score > 100) {
        throw std::out_of_range("score");
    }
}

int main() {
    int score = 120;

    try {
        validateScore(score);
        std::cout << "score=" << score << std::endl;
        std::cout << "valid=1" << std::endl;
    } catch (const std::out_of_range& error) {
        std::cout << "score=" << score << std::endl;
        std::cout << "valid=0" << std::endl;
    }

    return 0;
}

  1. score ← 85

    10int main() {11    int score→ 85 = 85; //@score=-5, 120

  2. try

    13try {14    validateScore(score85);15    std::cout << "score=" << score << std::endl;

  3. void validateScore(int score)

    4void validateScore(int score85) {5    if (score < 0 || score > 100) {

  4. validateScore(score);

    13try {14    validateScore(score85);15    std::cout << "score=" << score85 << std::endl;16    std::cout << "valid=1" << std::endl;17} catch (const std::out_of_range& error) {
    outputscore=85
valid=1

  5. return 0;

    22    return 0;23}

  1. score ← -5

    10int main() {11    int score→ -5 = -5;

  2. try

    13try {14    validateScore(score-5);15    std::cout << "score=" << score << std::endl;

  3. void validateScore(int score)

    4void validateScore(int score-5) {5    if (score < 0 || score > 100) {

  4. if (score < 0 || score > 100)

    4void validateScore(int score) {5    if (score-5 < 0 || score > 100) {6        throw std::out_of_range("score");7    }

  5. catch (const std::out_of_range& error)

    16    std::cout << "valid=1" << std::endl;17} catch (const std::out_of_range& error) {18    std::cout << "score=" << score << std::endl;19    std::cout << "valid=0" << std::endl;20}
    outputscore=-5
valid=0

  6. return 0;

    22    return 0;23}

  1. score ← 120

    10int main() {11    int score→ 120 = 120;

  2. try

    13try {14    validateScore(score120);15    std::cout << "score=" << score << std::endl;

  3. void validateScore(int score)

    4void validateScore(int score120) {5    if (score < 0 || score > 100) {

  4. if (score < 0 || score > 100)

    4void validateScore(int score) {5    if (score120 < 0 || score > 100) {6        throw std::out_of_range("score");7    }

  5. catch (const std::out_of_range& error)

    16    std::cout << "valid=1" << std::endl;17} catch (const std::out_of_range& error) {18    std::cout << "score=" << score << std::endl;19    std::cout << "valid=0" << std::endl;20}
    outputscore=120
valid=0

  6. return 0;

    22    return 0;23}