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<h1 id="use-macros"><a class="header" href="macros.html#use-macros">use macros</a></h1>
<p>which use cases valid for macros ?</p>
<ul>
<li>boilerplate coding
<ul>
<li>copy - paste / replacing style coding</li>
</ul>
</li>
<li>conditional coding
<ul>
<li>feature enabling / disabling depending on defined/not defined features in a globally accessible file
<ul>
<li>value based</li>
<li>state based</li>
</ul>
</li>
</ul>
</li>
</ul>
<p>macros are not good for true constant or compile time constants because they don't have memory address.</p>
<p>ok.. time to share some how to handle boiler plate coding with macros...</p>
<blockquote>
<p>preprocessor can replace macro args with used areas so you can think them like placeholders or aliases or variables but without type - just values</p>
</blockquote>
<blockquote>
<p>wrapping macro args with () is a good habit because you cannot be sure what passed into macro so best is use () with args as much as possible</p>
</blockquote>
<pre><code class="language-c++">
#define PROPERTY(type, name) \
private: \
type _##name; \
\
public: \
const type& name() const { return _##name; } \
void set_##name(const type& value) { _##name = value; }
struct MyS {
PROPERTY(int, id);
PROPERTY(std::string, name);
};
int main() {
MyS ms;
ms.set_id(101);
ms.set_name("hakan gedek");
std::cout << ms.id() << ":" << ms.name() << std::endl;
}
</code></pre>
<p>a long example which shows how to create a class with getter/setter impls, how to create an enum...</p>
<pre><code class="language-c++">#include <iostream>
#include <string>
#include <vector>
#include <memory>
#include <cassert>
// 1. Simple debug logging macro
#ifdef DEBUG
#define LOG(message) std::cout << "[DEBUG] " << __FILE__ << ":" << __LINE__ << " " << message << std::endl
#else
#define LOG(message) // Defines to nothing in release builds
#endif
// 2. Assert macro with better error messages
#define ASSERT(condition, message) \
do { \
if (!(condition)) { \
std::cerr << "Assertion failed: " << #condition << "\n" \
<< "Message: " << message << "\n" \
<< "File: " << __FILE__ << "\n" \
<< "Line: " << __LINE__ << std::endl; \
std::abort(); \
} \
} while (0)
// 3. Property accessors macro
#define PROPERTY(type, name) \
private: \
type name##_; \
public: \
const type& name() const { return name##_; } \
void set_##name(const type& value) { name##_ = value; }
// 4. Singleton pattern macro
#define DECLARE_SINGLETON(className) \
public: \
static className& getInstance() { \
static className instance; \
return instance; \
} \
private: \
className() = default; \
~className() = default; \
className(const className&) = delete; \
className& operator=(const className&) = delete; \
className(className&&) = delete; \
className& operator=(className&&) = delete
// 5. Factory method registration macro
#define REGISTER_PRODUCT(productId, productClass) \
static bool registeredProduct_##productClass = Factory::registerProduct(productId, \
[]() -> std::unique_ptr<Product> { return std::make_unique<productClass>(); })
// 6. String switch macro (C++ doesn't have native string switches)
#define STRING_SWITCH(str) const std::string& _switch_str = (str); if (false)
#define CASE(str) } else if (_switch_str == (str)) {
#define DEFAULT } else {
// 7. Automated class reflection-style macros
#define BEGIN_PROPERTIES(className) \
static std::vector<std::string> getPropertyNames() { \
std::vector<std::string> props;
#define PROPERTY_NAME(name) props.push_back(#name);
#define END_PROPERTIES \
return props; \
}
// 8. Enum-to-string conversion macro
#define ENUM_TO_STRING(enumType) \
inline std::string enumToString(enumType value) { \
switch (value) {
#define ENUM_VALUE(value) \
case enumType::value: \
return #value;
#define END_ENUM_TO_STRING \
default: \
return "Unknown"; \
} \
}
// Example usage of the macros
// Example with property macros
class Person {
PROPERTY(std::string, name)
PROPERTY(int, age)
public:
Person(const std::string& name, int age) : name_(name), age_(age) {}
BEGIN_PROPERTIES(Person)
PROPERTY_NAME(name)
PROPERTY_NAME(age)
END_PROPERTIES
};
// Example with enum-to-string macros
enum class Color { Red, Green, Blue, Yellow };
ENUM_TO_STRING(Color)
ENUM_VALUE(Red)
ENUM_VALUE(Green)
ENUM_VALUE(Blue)
ENUM_VALUE(Yellow)
END_ENUM_TO_STRING
// Example with singleton pattern
class Configuration {
DECLARE_SINGLETON(Configuration);
public:
std::string getDatabaseUrl() const { return "jdbc:mysql://localhost:3306/mydb"; }
};
// Example with factory pattern
class Product {
public:
virtual ~Product() = default;
virtual std::string getName() const = 0;
};
class ConcreteProductA : public Product {
public:
std::string getName() const override { return "ProductA"; }
};
class ConcreteProductB : public Product {
public:
std::string getName() const override { return "ProductB"; }
};
class Factory {
public:
using Creator = std::function<std::unique_ptr<Product>()>;
static bool registerProduct(const std::string& id, Creator creator) {
getRegistry()[id] = creator;
return true;
}
static std::unique_ptr<Product> createProduct(const std::string& id) {
auto it = getRegistry().find(id);
if (it != getRegistry().end()) {
return it->second();
}
return nullptr;
}
private:
static std::map<std::string, Creator>& getRegistry() {
static std::map<std::string, Creator> registry;
return registry;
}
};
// Register products
REGISTER_PRODUCT("A", ConcreteProductA);
REGISTER_PRODUCT("B", ConcreteProductB);
int main() {
// Using debug logging macro
LOG("Application started");
// Using assert macro
int x = 5;
ASSERT(x == 5, "x should be 5");
// Using property macros
Person person("John", 30);
std::cout << "Name: " << person.name() << ", Age: " << person.age() << std::endl;
person.set_age(31);
std::cout << "Updated age: " << person.age() << std::endl;
// Using reflection-style property listing
std::cout << "Person properties: ";
for (const auto& prop : Person::getPropertyNames()) {
std::cout << prop << " ";
}
std::cout << std::endl;
// Using enum-to-string conversion
Color color = Color::Blue;
std::cout << "Color: " << enumToString(color) << std::endl;
// Using singleton pattern
auto& config = Configuration::getInstance();
std::cout << "DB URL: " << config.getDatabaseUrl() << std::endl;
// Using factory pattern with registration macros
auto productA = Factory::createProduct("A");
std::cout << "Created: " << productA->getName() << std::endl;
// Using string switch macro
std::string fruit = "apple";
STRING_SWITCH(fruit) {
CASE("apple")
std::cout << "It's an apple" << std::endl;
CASE("orange")
std::cout << "It's an orange" << std::endl;
DEFAULT
std::cout << "Unknown fruit" << std::endl;
}
return 0;
}
</code></pre>
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