feature: Implemented Helper::setElement() (#310)

* feature: Implemented `Helper::setElement()`

This helper function can be used to get random items from a std::set
of objects.

* refactor: Use `Helper::setElement()`

Use helper function instead of rewriting code

* tests: Added tests for `Helper::setElement()`

include/faker-cxx/Helper.h

@@ -1,7 +1,9 @@
 #pragma once
 
+#include <algorithm>
 #include <functional>
 #include <numeric>
+#include <set>
 #include <span>
 #include <string>
 
@@ -67,6 +69,32 @@ class Helper
         return data[index];
     }
 
+    /**
+     * @brief Get a random element from a std::set.
+     *
+     * @tparam T an element type of the std::set.
+     *
+     * @param std::set of elements.
+     *
+     * @return T a random element from the std::set.
+     *
+     * @code
+     * std::set<char> chars{'a', 'b', 'c', 'd', 'e'};
+     * Helper::setElement(chars) // 'd'
+     * @endcode
+     */
+    template <class T>
+    static T setElement(const std::set<T>& data)
+    {
+        if (data.empty())
+        {
+            throw std::invalid_argument{"Data is empty."};
+        }
+        T item;
+        std::sample(data.begin(), data.end(), &item, 1, pseudoRandomGenerator);
+        return item;
+    }
+
     template <class T>
     struct WeightedElement
     {

src/modules/helper/HelperTest.cpp

@@ -4,6 +4,7 @@
 #include <regex>
 #include <stdexcept>
 #include <unordered_map>
+#include <vector>
 
 #include "gtest/gtest.h"
 
@@ -18,6 +19,24 @@ class HelperTest : public Test
 namespace
 {
 
+TEST_F(HelperTest, SetElement)
+{
+    std::set<char> chars{'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'l', 'm'};
+    std::vector<char> randomChars;
+    for (int i = 0; i < 30; ++i)
+    {
+        randomChars.push_back(Helper::setElement(chars));
+    }
+    for (auto character : randomChars)
+    {
+        ASSERT_TRUE(chars.find(character) != chars.end());
+    }
+}
+TEST_F(HelperTest, SetElementEmptyData)
+{
+    std::set<char> chars{};
+    ASSERT_THROW(Helper::setElement<char>(chars), std::invalid_argument);
+}
 TEST_F(HelperTest, ReplaceSymbolWithNumber)
 {
     std::string input = "123#456!";

src/modules/string/String.cpp

@@ -186,8 +186,7 @@ std::string String::binary(GuaranteeMap&& guarantee, unsigned int length)
         while (true)
         {
             // pick random char from targetCharacters
-            std::mt19937 gen(std::random_device{}());
-            std::sample(targetCharacters.begin(), targetCharacters.end(), &generatedChar, 1, gen);
+            generatedChar = Helper::setElement(targetCharacters);
 
             auto it = guarantee.find(generatedChar);
             // if no constraint on generated char, break out of loop