Added virtual protected functions to base_sink

include/spdlog/sinks/base_sink.h

@@ -30,7 +30,7 @@ public:
     base_sink(const base_sink &) = delete;
     base_sink &operator=(const base_sink &) = delete;
 
-    void log(const details::log_msg &msg) final
+    void log(const details::log_msg &msg) final override
     {
         std::lock_guard<Mutex> lock(mutex_);
         sink_it_(msg);
@@ -45,18 +45,28 @@ public:
     void set_pattern(const std::string &pattern) final override
     {
         std::lock_guard<Mutex> lock(mutex_);
-        formatter_ = std::unique_ptr<spdlog::formatter>(new pattern_formatter(pattern));
+        set_pattern_(pattern);
     }
 
     void set_formatter(std::unique_ptr<spdlog::formatter> sink_formatter) final override
     {
         std::lock_guard<Mutex> lock(mutex_);
-        formatter_ = std::move(sink_formatter);
+        set_formatter_(std::move(sink_formatter));
     }
 
 protected:
     virtual void sink_it_(const details::log_msg &msg) = 0;
     virtual void flush_() = 0;
+
+    virtual void set_pattern_(const std::string &pattern)
+    {
+        formatter_ = spdlog::make_unique<spdlog::pattern_formatter>(pattern);
+    }
+
+    virtual void set_formatter_(std::unique_ptr<spdlog::formatter> sink_formatter)
+    {
+        formatter_ = std::move(sink_formatter);
+    }
     Mutex mutex_;
 };
 } // namespace sinks