Changed error system to CRTP, rough draft

include/Errors.hpp

@@ -5,48 +5,84 @@
 #include <exception>
 #include <string.h>
 #include <string>
+#include <type_traits>
 #include <unordered_map>
 
 namespace nb {
 
 typedef std::unordered_map<unsigned int, const char*> ErrorCodeMap;
 
-class Error : public std::exception {
+template<class ErrorType>
+class ErrorBase : public std::exception {
 public:
-    Error(const unsigned int code=0, std::exception* const trace=nullptr) noexcept;
-    Error(std::string, std::exception* const=nullptr) noexcept;
-    Error(const Error&) noexcept;
+    static std::string lookup(unsigned int);
 
-    unsigned int code() const noexcept;
-    virtual const char* type() const noexcept final;
-    virtual const char* what() const noexcept override final;
+    virtual const char* what() const noexcept override final {
+        return static_cast<const ErrorType*>(this)->_msg.c_str();
+    };
+    unsigned int code() const noexcept {
+        return static_cast<const ErrorType*>(this)->_code;
+    };
 
-    template<typename NBError>
-    friend const char* ErrorCodeLookup(unsigned int);
 protected:
-    static const ErrorCodeMap ErrorCodes;
-    Error(
-        const unsigned int,
-        std::string,
-        std::exception* const,
+    ErrorBase() = default;
+    ErrorBase(
+        const unsigned int code,
+        std::string msg,
+        std::exception* const trace,
         unsigned int line=0,
         std::string filename=""
-    ) noexcept;
+    ) noexcept : _code{code} {
+         static_assert(std::is_same<const std::unordered_map<unsigned int, const char*>, decltype(ErrorType::ErrorMessages)>::value,
+            "const std::unordered_map<unsigned int, const char*> ErrorMessages must be "
+            "a class member."
+        );
+        static_assert(std::is_enum_v<typename ErrorType::ErrorCodes>, "enum ErrorCodes must be a class member.");
+        static_assert(std::is_same<std::underlying_type_t<typename ErrorType::ErrorCodes>, unsigned int>::value,
+            "enum ErrorCodes must be of underlying type unsigned int."
+        );
+        static_assert(std::is_same<const std::string, decltype(ErrorType::type)>::value,
+            "const std::string type must be a class member."
+        );
+
+        _msg = std::string(ErrorType::type);
+        _msg += ":" + std::to_string(code);
+        if (line && filename.size()) {
+            _msg += " in \'" + filename + "\':" + std::to_string(line);
+        }
+        _msg += "\n\t" + msg;
+        if (trace) {
+            _msg += "\nTraceback - " + std::string(trace->what());
+        }
+    }
     
-    const char* _type;
     const unsigned int _code;
     std::string _msg;
 };
 
-template<typename NBError>
-const char* ErrorCodeLookup(unsigned int code) {
-    for (auto kv : NBError::ErrorCodes) {
-        if (kv.first == code) {
-            return kv.second;
+
+class Error : public ErrorBase<Error> {
+public:
+    Error(unsigned int code, std::exception* const trace=nullptr) 
+        : ErrorBase<Error>(code, ErrorBase<Error>::lookup(code), trace) {}
+    
+    enum ErrorCodes : unsigned int {
+        UNDEFINED, BADERRORCODE
+    };
+    static const std::string type;
+    static const ErrorCodeMap ErrorMessages;
+
+};
+
+template<class ErrorType>
+std::string ErrorBase<ErrorType>::lookup(unsigned int code) {
+    for (auto kv : ErrorType::ErrorMessages) {
+        if (kv.first==code) {
+            return std::string(kv.second);
         }        
     }
 
-    throw Error(666);
+    throw Error(Error::ErrorCodes::BADERRORCODE);
 }
 
 } // namespace nb

src/NBCoreUtils/Errors.cpp

@@ -3,56 +3,11 @@
 namespace nb {
 
 // class Error
-const ErrorCodeMap Error::ErrorCodes = {
-    {0, "Undefined error."},
-    {666, "Unrecognized error code."}
+
+const std::string Error::type =  "Error";
+const ErrorCodeMap Error::ErrorMessages = ErrorCodeMap{
+    {ErrorCodes::UNDEFINED, "Undefined / general error."},
+    {ErrorCodes::BADERRORCODE, "Unrecognized error code."}
 };
 
-Error::Error(
-    const unsigned int code,
-    std::string msg,
-    std::exception* const trace,
-    unsigned int line,
-    std::string filename
-) noexcept : _code{code} {
-    _msg = std::string(type());
-    _msg += ":" + std::to_string(code);
-    if (line && filename.size()) {
-        _msg += " in \'" + filename + "\':" + std::to_string(line);
-    }
-    _msg += "\n\t" + msg;
-    if (trace) {
-        _msg += "\nTraceback - " + std::string(trace->what());
-    }
-}
-
-Error::Error(const unsigned int code, std::exception* const trace) noexcept
-: Error(code, ErrorCodeLookup<Error>(code), trace) {}
-
-Error::Error(std::string msg, std::exception* const trace) noexcept
-: Error(0, msg, trace) {}
-
-Error::Error(const Error& cp) noexcept
-: _type{cp._type}, _code{cp._code}, _msg{cp._msg} {} 
-
-unsigned int Error::code() const noexcept { return _code; }
-
-const char* Error::type() const noexcept { return this->_type; }
-
-const char* Error::what() const noexcept { return _msg.c_str(); }
-
-/* constexpr const char* Error::lookup(unsigned int code) noexcept {
-    char* ret = new char[512];
-    switch(code) {
-    case 0:
-        strcpy(ret, "General ");
-        strcat(ret, this->type());
-        break;
-    default:
-        strcpy(ret, this->lookup(code));
-        break;
-    }
-    return ret;
-} */
-
 }

tests/ErrorTest/main.cpp

@@ -3,29 +3,32 @@
 
 using namespace nb;
 
-class TestError : public nb::Error {
+class TestError : public ErrorBase<TestError> {
 public:
-    TestError(unsigned int code, nb::Error* const trace=nullptr) : _type("nb::TestError"), Error(code, ErrorCodeLookup<TestError>(code), trace) {}
+    TestError(unsigned int code, std::exception* const trace=nullptr) 
+        : ErrorBase<TestError>(code, ErrorBase<TestError>::lookup(code), trace) {}
     
-    friend const char* ErrorCodeLookup<TestError>(unsigned int);
-
-protected:
-    static const nb::ErrorCodeMap ErrorCodes;
-    const char* _type;
+    enum ErrorCodes : unsigned int {
+        A, B, C, D
+    };
+    static const std::string type;
+    static const ErrorCodeMap ErrorMessages;
 };
 
-const ErrorCodeMap TestError::ErrorCodes{
-    {0, "Hey!"},
-    {1, "How"},
-    {2, "You"},
-    {3, "Doin"}
+const std::string TestError::type="TestError";
+const ErrorCodeMap TestError::ErrorMessages{
+    {TestError::ErrorCodes::A, "Hey!"},
+    {TestError::ErrorCodes::B, "How"},
+    {TestError::ErrorCodes::C, "You"},
+    {TestError::ErrorCodes::D, "Doin"}
 };
 
 int main() {
-    TestError a(0);
-    TestError b(1, &a);
-    TestError c(2, &b);
-    throw TestError(3, &c);
+    TestError d(TestError::ErrorCodes::D);
+    TestError c(TestError::ErrorCodes::C, &d);
+    TestError b(TestError::ErrorCodes::B, &c);
+    TestError a(TestError::ErrorCodes::A, &b);
+    throw Error(Error::ErrorCodes::UNDEFINED, &a);
 
     return 0;
 }