add Chapter 15 - runtime observer implementation

Chapter15/observer/app/src/main_observer_rt.cpp

@@ -0,0 +1,91 @@
+#include <cstdint>
+#include <cstdio>
+
+#include <functional>
+
+#include <stm32f072xb.h>
+
+#include <hal.hpp>
+#include <stm32f0xx_hal_uart.hpp>
+#include <uart_stm32.hpp>
+
+#include <retarget.hpp>
+
+#include "etl/vector.h"
+
+class subscriber {
+public:
+    virtual void update(float) = 0;
+};
+
+class display : public subscriber {
+public:
+    void update(float temp) override {
+        printf("Displaying temperature %.2f \r\n", temp);
+    }
+};
+
+class data_sender : public subscriber {
+public:
+    void update(float temp) override {
+        printf("Sending temperature %.2f \r\n", temp);
+    }
+};
+
+class logger : public subscriber {
+public:
+    void update(float temp) override {
+        printf("Logging temperature %.2f \r\n", temp);
+    }
+};
+
+class publisher {
+public:
+    void register_sub(subscriber * sub) {
+        if(std::find(subs_.begin(), subs_.end(), sub) == subs_.end()) {
+            subs_.push_back(sub);
+        }
+    }
+
+    void unregister(subscriber * sub) {
+        if(auto it = std::find(subs_.begin(), subs_.end(), sub); it != subs_.end()) {
+            subs_.erase(it);
+        }
+    }
+
+    void notify(float value) {
+        for(auto sub: subs_) {
+            sub->update(value);
+        }
+    }
+
+private:
+    etl::vector<subscriber*, 8> subs_;
+};
+
+int main()
+{
+    hal::init();
+
+    hal::uart_stm32<hal::stm32::uart> uart(USART2);
+    uart.init();
+
+    retarget::set_stdio_uart(&uart);
+
+    logger temp_logger;
+    display temp_display;
+    data_sender temp_data_sender;
+
+    publisher temp_publisher;
+    temp_publisher.register_sub(&temp_logger);
+    temp_publisher.register_sub(&temp_display);
+    temp_publisher.notify(24.02f);
+
+    temp_publisher.unregister(&temp_logger);
+    temp_publisher.register_sub(&temp_data_sender);
+    temp_publisher.notify(44.02f);
+
+    while(true)
+    {
+    }
+}